I dont know if SD will make a difference. Certainly worth a shot. To me, it sounds like a high speed fueling issue with the injectors, or the ignition system. An ignition analyzer would really help at this point. Maybe call around to various shops and see if one has a dyno and an analyzer. Could save you a lot of time and headaches. Id still be leaning towards the ign. since it still does it with the injectors static.

Probably one of the best things I ever did was converting to the later PCMs that use the vortec dist. with remote module. Thats much more reliable. Ive yet to have any issues with it, and it works smoothly out to 6k. Much better system as it has fewer parts, more robust dist. (if you get a billet one), and a cooler running module.

As far as other options, why the megasquirt? Going to DIS? Even in stock form, the $0D can do PFI with only minor changes.

 

Its back in SD and I'm not going to say its fixed but it ran significantly better than it has in years. It felt very torquey and pulled past 5000 pretty effortlessly. It did begin to lean out pretty bad at that point but I'm running on the VE tables I last used with speed density which was with the little comp flat tappet cam, just higher fuel pressure this time, 40 psi to be exact. I'm going to keep playing with it and see what happens. I need to get a new ADX made up so I can datalog the VE tables and what not but thats minor stuff. Even then I think I will keep my driving locally until I can start to build up some trust in it again. Its still doing some weird stuff with the IAC and fuel trims near idle but the battery is now disconnected and hopefully a nice long PCM reset will clear some of the hiccups up.

 

The reason for that is probably because the SD doesnt see all the misfires like a MAF does. If you start misfiring with MAF, it quickly compounds the problem. It may make it easier to diagnose what is going on, though, as SD cant see any rapid flow changes, just manifold pressure.

I think a lot of your problems could have come from constantly messing with the fuel pressure w/o properly updating the injector constant. When you tune the SD, make sure you set the injector constant properly. You could get into the same issues all over again if the fueling gets screwed up. The FI is only as good as the calibration that it has.

Have you considered trying it on an ignition analyzer? That could at least rule out any potential ignition problems. All my problems with my last setup where all related to the junk HEI ignition system. They just dont work properly at high engine speeds. I never could tell if it was the dwell, or just the modules overheating, but I never had my old CC-HEI work for more than a week at a time. You could just be band-aiding the actual problem by changing the fueling.

 

A misfire will report a fuel problem. All that unburned fuel/air still registers on the O2 sensor.
Best case, if the constants do not reflect what's actually mechanically being delivered, then you don't really know, because all of everything is based on a lie.
You *can* end up with a tune that appears to work, but making any future adjustment remains a by gosh and by golly crap shoot.
Personally, one thing at a time. If I suspect ignition, absolutely nothing else changes until I'm satisfied ignition is correct. If I suspect fuel, same routine. Absolutely nothing else, to avoid adding in more unknowns, and complicating the problem by compounding errors, real or imagined. ( but that's me )

 

It will skew the fuel at P/T, not so much at WOT, depending on the calibration. The O2 is pretty heavily filtered, though, so it cant see individual misfires.

The MAF, though, can. The PCM updates the MAF sensor readings every time a cylinder fires, so if one misfires through the intake, it will disrupt the MAF readings and make the misfires worse.

 

Depends. Mine can detect individual misfires, but can't tell me which cylinder.
The filtering results in an over-all mixture error, lean as I recall, from excess O2, and the ECM responds by richening up the mix ( raising the INT, and possibly the BLM as well ) to counteract the lean condition it thinks it sees.
I've had misfires burn out catalytic converters because of this, due to flooding, and compounding the problem very quickly.
Of course, I'm SD TBI, not MAF.

If he's really going static, he's probably VERY rich, as static injectors flow their full rating, or what the pump can deliver, whichever is less.
We both agree ( methinks ) that accurate constants reflecting what the injectors are really delivering is still best, eliminating a dozen or so dependent variables.

 

There's a lot of really good technical information in this thread and some of the most knowledgable people on the subject here. This is why I have been reading this thread for years...

I just want to tell a story that happened to me at Englishtown NJ Raceway Park back in about 1977. I had a BB Nova, we had built in high school auto shop completed a few months before Hot ROd Magizine had an article on how to fit a BB in a 67 era Nova.

One night we had problems running and the car was breaking up WOT. Did several things and several runs, no change. A guy walks up and starts talking to us in the pits and says 'Change the plugs" We say they only have 6-8 runs on them. He laughed and said change the plugs. A few runs later we change the plugs! Bingo! No breaking up. After that we only ran a set of plugs at the track 4 runs and never had the problem again. Could run the old plugs on the street for another year.

So have you changed your plugs?

And is there a differnce in todays plugs that would aleviate this problem? Run all year on plugs but WOT at track conditions and they would break up/misfire? I still never knew why? Still never knew who the guy was either but he came by about a month later and says "Cars running good!" we talked and he said put a couple more PSI in your slicks. We say but we just got them down to hooking up good! He says let them spin a little. POOF! half a second off out ET.

 

The why is that it takes more energy to arc the gap under higher pressures.
What's the in-cylinder PSI at WOT at max torque ? At max VE ? At max HP ?
A typical street engine at idle might take 11KV or so to fire reliably.
That same engine at WOT might take 18 or so.
If your ignition goes marginal at 16, well, you can guess what happens.

Sure !
What's the diameter of the tire at 4 PSI ?
Now, what's the diameter at 6 PSI ?
Allowing a "little" spin at launch, but gaining a good deal more at the big end.
Not as much as changing a rear end gear, but in that direction !

 

If you use some theoretical equations (Paschen's law), your looking at something like 30-40 kV to fire the plugs with a .060" gap in the cylinder when the engine is under full load. Obviously it will probably be a bit different in reality, but its a lot more than the 8-10 kV that it takes in open air. Having a module that can deliver the proper ammount of needed current to fire the coil is crucial. If the ignition isnt up to it, than not much else matters. The spark wont reliably jump the gap when the ignition system fires, and the engine will misfire, break up, and generally not make good power.

I had this with the HEI system. For me, it just didnt work at high RPMs over long periods. With each module it would initially be good, but it would degrade over time, and cause a weak spark. I think what happened was the power transister would degrade, and its saturated resistance would increase with time as the junction broke down from heat or whatever. Changing the fueling a bit to lower the cylinder pressures would help fix some of the misfires and loss of power, but it was just a band-aid for a weak ignition. Replacing the stock ignition with a later model design was the best power mod I ever did.

I still think oldred should put it on an analyzer to rule out the ignition before proceeding.

 

An easy test for a weak ignition is to put some fresh plugs in with a tighter gap. If now running at 035, gap at 030. Just use regular plugs, nothing fancy.

RBob.

 

On one occasion, some breakup at high RPM, progressively getting worse as I tried things, I pulled the super-duper extra platinum plugs gapped at 60 and replaced them with off-the-shelf cheapest Autolite they had, gapped about 15 just to see.
LAWRDY what a difference ! Ran like a scared rabbit !
Couple weeks later, wouldn't fire at all. ( confirmed with an inductive timing light )
Divorced coil HEI and careful examination showed rust penetrating the laminates of the coil frame.
New coil, back to 60 gap on the right ( more expensive platinum plugs ) and away we go ! Two years ago, as I recall. Same platinum plugs still in it.
It really was ignition !

 

Time for a not too eventful update. It sat all week with the battery unhooked to make dang sure all learned info was gone. Flashed it with basically the exact same tune only with some top end VE changes and smoothed the table a little overall. It ran pretty nice but was running lean under heavy load. By lean I mean by 4500 rpms it was in the 15:1 and heading leaner range. I went ahead and took it on up to 6000 just to see and saw 18:1 and it was cutting out some as it should do that lean. I realize its not good to run it that lean but if it melts down it melts down. At least I have some data now. Also at the same time at 4500 my pulse width was very low around 3.13 and falling as the rpms increased. By 6000 it was in the mid 2s if I remember right. The VE tables are nearly maxed and the pressure is there, just not the flow. I looked at my injector offset table and at what is supposed to be the stock 454 table and it seems rather low at 11-15 volts being in the 282 usec range. I changed that area to 650 usec and will try it tomorrow and see what happens.

 

I'm with the dimented one, a scope would tell volumes, even about mixture.

Make sure to keep an eye out for falling fuel pressure..

Let us know.

 

I understand. Been there. Really, 30 seconds should be enough.

My thing is lean cruise these days, so I've experimented with deliberately going lean, but not at high load like that.
Frankly, I'm surprised it'd fire at all THAT lean !

Again, I understand the desperation to gather some kind of data, even at risk.

Somewhere, I've got Rbob's chart of RPM vs time, and what's static at what RPM.
I'll try and find it, if you don't find it first.

If I was seeing what you're seeing, I'd be inclined to set up a test case.
Plumb an injector to spray into a can. Lock it on at whatever minimum voltage holds it open, and measure the actual flow for a minute, and probably the pressure at that flow.
It does sound like you're running out of fuel, so why is that ?
Either the injectors are not what you think they are, or the pump can't keep up.
For me, it was the pump, so I added a booster in-line with the tank pump.
Now, the tank pump merely primes the in-line, and I got flow !

Before I did that, I'd close the plug gap down to about .015 and do a quick run just to be sure the collected data is consistent.

 

The change to the injector offset will mostly affect areas of small PWs. This would be where the VE table is low in the low MAP areas. They will get richer.

The mid 2 msec at 6,000 RPM is giving up a lot of fuel. I am going to assume that the PCM is still using the standard TBI alternating fire on each plug firing for the following.

At 6,000 RPM each injector gets fired twice (8-cylinder here). So there is 5 msec of time available. For 85% DC, the injector would be open for 4.25 msec. As you can see there is a bunch of fuel time available.

Since the VE table is getting maxed out, need to tell the PCM that the injectors are smaller. This will cause the PW calculation to increase the PW across the board.

Note that the largest PW is right above peak torque. The PW will fall off from there, but the injectors are being fired more frequently to provide additional fuel to feed the HP.

RBob.

 

Wanted to drop a note in here about data logging injector PWs. The PCM may not be including the injector offset compensation in the ALDL stream. I know the ECMs such as the '7747 didn't, so it had to be added in mentally when looking at the data log.

Need to find out if the code base you are using does or not, and act accordingly to get the actual PW used for the DC% calculation.

RBob.

 

With the injector offset at 747 usec it was significantly better. Still not perfect but tons better. It actually revved to 6350 at part throttle (didn't mean the WOT shift requirements I guess) and bounced the rev limiter but it pulled right up there none the less. The AFR was a little sketchy in places but not too bad. The pulse width was pretty low around 2.75 so plenty of fuel there. It made the VE tables rich overall so I did a global VE table adjustment as well as telling the PCM its running at 30 psi rather than 40 to try and keep the PW from getting too short and disabled PE so if I remember right I will be able to log the BLMs clear up to 6000+ and see what the fuel table is really doing.

 

Why do you need to take it up so high? What kind of cam do you have in it currently? The LT4 hot cam? The higher you rev it, the harder it is on the injectors and ignition to keep up. 6k should be sufficient to get to the peak power of the engine. More than that really stresses things, especially if you have a stock rotating assembly.

 

Well, no !
Yes, you will be able to discern the general shape of the VE map, but that's all.
The actual values will be meaningless, because the numbers will be based on a configuration that you do not have.
This is precisely why I and Dimented have suggested that you don't lie to the ECM.
If you were feeding the ECM the injector and fuel pressures you really do have, then the values learned would be real. This way, they are not.
Also, because the variables are different, you won't be able to simply convert to true values, as they won't be linear.

 

Holy mackerel, this turned into quite a thread! Nice!

And my car is far from running:

https://www.thirdgen.org/forums/ltx-...-ever-v-4.html

 

Yes, well, some of us try to instill in the casual lurker that while some techniques may "work" in select circumstances, they should not be interpreted as a generally correct approach to solving for a single variable.
The preferred way to resolve an issue is to resolve the issue, not to add a compounding problem that appears on the surface to bandaid the original issue at the expense of an unknown number and severity of more unknown issues.

 

LoL gotta love them lurkers

 

Like I said before, set the injector flowrate to that for the ACTUAL flowrate at the current PSI, and then start tuning. Dont just slap something in there strictly to keep the PW low. It also wont help at idle. while it may keep the pulsewidths above the 1 msec mark, it will make the engine run rich at idle, which will waste fuel, foul the plugs, etc.

The required pulsewidth is ENTIRELY dictated by the fuel required by the engine, and the injectors actual flowrate. Your goal isnt to get X pulsewidth, but to deliver the proper ammount of fuel to obtain the desired fuel air ratios. If you turn up the pressure, you also need to change the injector constant.

Right now, your just throwing darts. The whole point of tuning is to match the calibration in the PCM to the engine, not to get a short pulsewidth, or to take a guess and see if it will make it run better. Set the pressure to something that will work for both idle and WOT, set the injector constant to what it should be, and use a wideband to calibrate the VE tables. Dont use the BLMs at high RPMs. Those are only marginally accurate, and require a lot of samples to get it right. Use a wideband.

If the WB data looks good, the PWs arent going static, and it still misfires, its not the fueling. Start looking elsewhere. Dont band-aid it by changing things until it sort of runs ok.

 

First of all I am using the correct injector flow rate calculation for the actual pressure and have been for the last week. I just reduced the fuel pressure to 35 psi from 40 psi and have a corrected flow rate of 16.13 I believe the unit is grams per second. I set my Power enrichment enable TPS to 100% across the boards and I am now able to datalog my BLMs in closed loop at 14.7:1 all the way to red line. I'm taking baby steps with it but at high load around 4000 it was running a little lean yet and the BLMs were in the 147 range so it was adding fuel as needed. I could both hear feel the change as fuel was being added. That being said I am using my wide bands narrow band output in place of my actual narrow band sensor. The data at high speed and load may not be completely accurate but it is accurate enough to tell me what I know and that is that its still lean. I'm still making educated guess based adjustments to the VE tables and actually have it pretty close below 3000. At 2200 at 70 mph it was running right on 127 as a matter of fact. A little rich below 2000 but all that will work out in the end. Here is a screenshot of what the VE table looks like after the latest changes that I won't test until tomorrow. It should get me pretty close. The reason for lowering the fuel pressure was very low pulse width at low engine load. I was getting into the .40 range and the injectors seemed to be having trouble pulsing a short enough amount of time to deliver the right amount of fuel, sort of like static in reverse. The main thing though is that its no longer misfiring.

 

The fueling is probably a lot closer now that your using the proper constants. That should help at least keep the fueling consistant at load, and prevent the engine from being potentially drowned in fuel. The injector constant is in grams/sec, FWIW. The calcs for the MAF and the SD work the same between the stock $0D and my code. Just the MAF is used to derive the cylinder airmass rather than the VE table.

IIRC, you dont have your EGR. Why not put the wideband into the linear EGR output? That way you can have it in your datalog. You can even set the ADS to convert the voltage into an AFR, and have the actual and desired AFRs next to eachother in the datalog. Thats how I had mine set up. That will save you from having to run it so lean at high load. That can really dump a lot of heat into the ex. valves and pistons. The CL routine swings about 14.7, so it could potentially be much leaner than stoich.

Its also entirely possible that it may misfire again when the fueling richens up. That causes the cylinder pressure to increase as it also increases the VE and quantity of gases generated during the combustion process. Hopefully it doesnt, but its a possibility. Keep us posted as to the results.

 

Well its doing it again. The air fuel ratio was running right at 14.4:1 and it pulled great until the 4500 range and started bucking and missing. The pulse width was good around 3.45 or there about and everything looked ok. I just don't get it. It runs so damn good up until that point and even then its still pulling pretty hard considering its running half retarded. If I had a lab scope and knew how to use it sure I could do that but I don't. I just have a hard time believing two totally different types of distributors could produce the exact same results and one being damn near new. I bet that large cap hei doesn't have but 2000 miles on it if even that. Its either got to be mechanical IE lifters pumping up/collapsing or electrical. Somewhere a page or two back a guy mentioned having the same type of issues and he ended up having bad wires/high resistance going from the ignition module to the PCM. It very well could be. The harness is 16 years old afterall and I've seen bad spots in harnesses that don't move, are inside completely out of the weather and not but a few years old. I guess its just cheap wire and sometimes they are made with breaks in them that when the time comes makes an open. I suppose its time I start doing some volt drop testing on the harness and see. Still it all goes back to it didn't do this before I put the LT4 hot cam in it and if I remember right it didn't do it right away with it either but it was after that cam went in I started having these problems. My comp hydraulic flat tappet lifters were always noisy but it would turn to 6000+ just fine if I wanted it to. It really didn't pull there but it did happen once or twice. Actually when I put the LT4 hot cam in I still ran Mystic 15w 40 oil for a while and then I think at the next oil change went to Mobil 1 5w 30. I'm half tempted to go back to 15w 40 or maybe even 20w 50 and see what the damn thing does.

 

14.4:1 might be ok for idle or cruise, but it's way lean for acceleration or load.
11.8-12.8 is normal for those conditions.

We are talking about an engine diagnostic scope, not a lab scope.
It will show conditions of both primary & secondary ignition.

 

Im using 5W-40 with my morel roller lifters. They bleed down faster than the stock ones, and dont work as well with the lower viscosity oils. They basically bleed down and tick. It doesnt cause any high RPM misfires, though.

A quick check of the lifters is to go out by the engine, and take the engine up to about 5k and see if the lifters start to clatter. If theyre bad enough to cause a misfire, you should be able to hear them clearly if theyre having problems staying pumped up, which is a possibility. I had it happen to one of my old crappy chinesium lifters that I was using with my isky flat tappet. The metering disk shattered, and caused the lifter to go completely flat. Made a hell of a lot of noise.

Engine problems aside, the most likely cause is the ignition. It could also possibly be an issue with the injector drivers in the PCM as well. Its possible that they could be failing. These are two things that you would need test equipment to see.

Also, how dirty is the base of the distributer? Is the clamp and the area around the intake where it bolts down clean? The reason I ask is that there is NO dedicated ground path with the HEI ignitions. The ground is solely through the distributor base, and through the hold-down clamp. If the base, clamp, bolt, or intake are dirty, then you will have a weak ignition. You can rule this out by taking some wire, and running it directly to the distributor. Clean a spot on the shaft portion of the housing, and take some bare or stripped copper wire (18 gauge is probably good) and clamp it to the base with a hose clamp. Run the other end to a nearby ground such as the block, or a ground strap, and make sure it has good contact when you secure it. If the misfires go away, then its a grounding issue.

 

I gotta come back to close down the plug gap A LOT to around .015 or so, and try that.
It can tell you more than you think !

 

I was just thinking the same thing. Close down the gap and see what happens. Oldred, are you running plugs for vortec heads? Stock they come gapped at .060". Works fine with the vortec ignition, but the gap might be a bit much for the HEI stuff, especially if its getting old.

 

Might be a bit off-topic, but since this thread is so full of nice tech info i guess it won't hurt to ask this as well =)
I keep reading that too loose gap makes it hard for the spark to arc over. That got me wondering, would a plug gap too small hurt anything? Also, 0.060 is a lot but if the Vortec ignition can do it, i guess it shows that this one has a lot of spark energy / high voltage to make the arc with a gap that big.

 

I would say you would want no tighter than stock on the plug gap unless you are running a power adder. Even a stock engine seems to respond better to a little wider gap.

Here is what I've gotten done in the last week. I bought new plugs, NGK TR55s. I was considering getting rapid fires but I couldn't see paying 5 bucks for a copper plug when iridiums weren't much more and NGKs are perfectly fine if not better. They were pre gapped at .055 and I set them all to .050 which should still be fine for the HEI to handle. I took my distributor hold down bracket off and it had that sort of tarnished rusty grimy appearance bare steel gets, the kind where if you were to try and ground a test light on it you would have to scratch around on it to get some shiny steel showing before it would ground. I took it to the wire wheel, it and the bolt both and reinstalled. If I can find a spot on the distributor housing I'm going to install a permanent ground from it to the second distributor hold down bolt hole in the intake. I still need to put the plugs in and also am going to change the TPS. A while back late one night around 2 AM I was heading home and the converter started cycling and it started jumping between 3rd and 4th for no reason. I've got a known good one so I might as well get that swapped out too.

 

Tighter gap will allow the ignition to more easily fire as the gap will break down at a lower voltage. But, its a diminishing returns things, and may cause issues if its too tight. It can also increase EM interference as it will increase the current through the wires when the plugs fire.

 

Yes, but you'd have to be in the 1/2 inch range with modern ignition systems, or under a tremendous amount of pressure. ( 20:1 comp ratio, or higher )
Of greater concern, is that it becomes "easier" for the coil to arc over internally, and destroy itself, or arc through the wires, etc. Once an arc occurs someplace other than at the spark plug, the damage is done. Car parts don't heal on their own.

OK, spark theory....
A spark plug serves two purposes. One is to start the fire. The other is to plug a hole in the head. Everything else is secondary.
Plugging the hole, obvious.
Lighting the fire, here we go.....

You want as much flamable mixture present within the gap when the spark occurs, to increase the reliability of something catching, and starting a fire.
The wider the gap, the more likely there is a good number of both gasoline and oxygen molecules within the gap, and hopefully in a ratio conducive to burning, but the wider the gap the more likely the coil arcs internally.
At very high speeds, a too wide gap can cause enough turbulence to be present within the gap to actually blow the spark out, if the ignition is weak.
At the other end, a gap down around .00001 or so, the number of molecules in the gap is ( obviously ) many orders of magnitude less, decreasing the chances of having a combustible mixture present when the spark occurs, but also taking much less from the ignition to cause a reliable spark, and shielding the gap from any turbulence.
Without getting to long winded, conclusions become as wide a gap as your ignition can reliably fire in the presence of compression pressures and turbulence will give you conditions most likely to ignite the fuel, which is the objective, yet not so wide that the ignition destroys itself by arcing anyplace other than at the plug. In the real world, this is somewhere between 0.020 and about 0.100 in almost all cases. ( possibly wider with coil on plug, depending on the internal construction of the coil itself )
So, if your ignition is going weak, closing the gap to 1/2 will reduce ignition system demands by a factor of 4 ! This is why I'm suggesting that he close his gap down to .010 or so as a test. ( it's a square law relationship for voltage and current demands )
Wide gaps will ( if they are going to at all ) misfire at high speeds due to turbulence and pressure combined with weak ignition system, or causing in-cylinder spark voltage demands to get so high that the arc occurs elsewhere, damaging the ignition system. Close gaps misfire at low speeds, like idle, or cranking, because there isn't enough turbulence to blow a flamable mixture into the gap.
Because this whole thread is about misfire above 4000 RPM, I still think a test at something like .010 or .015 is in order to expose deficiencies ( if any ) in his ignition system at high speed. If the breaking up goes away, then it's definitely an ignition problem. If it doesn't, at a .010 gap it's definitely NOT an ignition problem. In my mind, conclusively discovering whether or not it is an ignition problem is both easy, and a definitive step in the right direction.
*IF* it's an ignition problem, *then* replace the plugs first. At 0.010 gap even junk plugs will still fire reliably.
But, that's me..........

Addendum....
Close gaps also cause a much smaller ( physically ) flame kernel when the fire starts, and can slow the build up of the flame front to the point of requiring an extra 2 or 3 degrees advance. Not really a concern in this case, but just an additional point of information.

 

Once again more disappointment. New plugs, different tps and a nice clean shiny distributor hold down clamp. Still bucking and acting stupid as ever, actually probably worse. It seems to be getting just a little worse each time I drive it and its getting to the point I never drive it because I don't feel I can trust it anymore. Anyway now its doing it at light speeds to like going down main street where the speed limit is 20 mph. Just barely on the gas getting up to speed it bucks hard on the 1-2 shift and then catches itself. Once in 2nd at steady throttle, steady MAP, steady IAC, steady pulse width it will randomly start bucking to the point it feels like I've hit the fuel cut off (this is at 20 mph) and the pulse width will drop for no apparent reason and it will show lean because its basically shut the injectors off. I don't know what to do. I'm wondering if its some sort of RF interference but I'm not sure what it would be coming from. My PLX wideband controller is about 4 inches from the PCM but I don't recall it magically triggering this issue when I installed it. I really don't know where to go from here. It acts like it could be something corrosion related due to the fact it seems to get worse and worse as time goes on. I may just pull the damn harness and completely gut it and volt drop test every wire and make sure its all good and wrap it with tin foil and tape to keep out any RFI.


I've been thinking here. Are there any known issues with the G1 adapters from Craig Moates? Back before I got my emulator I started having connection issues with the ZIF socket which was later eliminated when I installed the emulator. I think it was the very same day I installed the emulator that I had drove it to work and on my way home that evening after taking off from a stop light it coughed about 3-4 times like someone had shut the fuel off then it took off like nothing had ever happened. I'm wondering if I'm still not getting some intermittent connection issues somewhere within the adapter. I've tried a known good PCM and still am using it and that made no difference.

 

I can attest to the higher voltage part. With a .060 gap, I have corona discharge around all the ignition system components that carry high tension. They all have a faint purple glow around them when you open the hood at night. Pretty creepy looking. Runs great, but really taxes all the insulation.

 

If you have your checksum enabled, and you dont get a blinking SES, I wouldnt worry about that.

As for the rest of it, the fact that its getting worse is a good thing. Now that its no longer intermittent, you can diagnose it easier. What happens when you pop another module in it?

 

I don't know. This distributor uses a different module than the small cap does. I just can't imagine it being the distributor since an entirely different brand new one really had no effect on the condition. Initially I thought it did and it did make it run better overall but its still there. I think I may pull the fuse on my wideband, my MAF sensor as its still hooked up and producing a signal although the wire isn't pinned, and cut out the wires tied into the VSS wires that were used to reroute it to pins F2 and F3 since those are just laying loose and taped up as well. I just don't think its ignition. Normally when you get a cylinder that drops out like when you have a bad plug wire or a cracked plug its a very abrupt quick little jolt of the engine especially at highway speeds. This is a lot smoother than that.

 

That's getting pretty intense ! I have no such glow running .060 routinely, but when I do run 0.100 gaps ( has to do with using the spark plug as the sensor for in-cylinder pressure measurements, and other such esoteric things ) things get dicey.
I gotta wonder in your case, if the glow is corona due to voltage ( which is an energy loss ) or due to induction from current ? The quick check ( again ) is to close down the gaps about 1/2 and see if the glow goes away. If it does, it's voltage. If not, it's current, and a really hot ignition !

At the other end, close gaps ( to eliminate high speed misfire ) is exactly why the MSD multi-strike ignition was invented ! To eliminate low speed ( below 3000 ) misfire due to small gaps.

 

Although I agree, I will add that I've had, at one time or another, random failure problems with every adapter, eeprom, ZIF socket, that I've ever run, except for eprom chips, and the EBL flash.
Almost all of them did produce at least one blink on the SES light, but a very few didn't.

 

The more I think about it the more I'm convincing myself that it could be the G1 adapter causing all the problems. Back when I used chips and the zif socket it wasn't unusual to plug one in and go for a drive and below say half throttle it be completely fine or it may go 5-10 miles then all of the sudden start acting to and try to die or go into limp mode. I kept thinking I was getting bad burns and finally realized if I pulled over and unlocked the zif and wiggled the chip and relocked it that it would go ahead and run. When I got rid of the zif and went with the emulator I figure all the problems would be gone. Like I said one on the very first things it did with it installed was cough 3-4 times for no apparent reason and then seemingly be fine from then on. As time went on it started acting more and more unpredictable to the point now it likes to randomly lean itself WAY out to the point the BLMs are in the 90s then it will start adding back like nothing ever happened. Also sometimes when I datalog I get a lot of sudden blips in the datalog and the digital gauges on scannerpro will peg and I accumulate a lot of errors and then other times it will datalog without a single hiccup. If it would run on the stock chip I would plug it in directly and see what happens but it won't. One more thing. When I first started tuning I went quite a while without a zif socket and only the G1 and was plugging and unplugging chips from it pretty often and it wasn't really meant to be used like that. I wonder if I didn't wear the contacts some which eventually lead to where I am at now.

 

ive been following your thread for awhile now hoping to see if you could work out the bugs. sad to see you have a worsening problem. i dont have much to offer but maybe it can help a little. years ago i had a problem with breaking up at higher rpm's, it wasnt until i tore down the engine and realized that there wasnt enough clearance in the valvetrain, the retainers were contacting the guides. i thought it was floating the valves, but i had pretty aggresive springs and figured it was something in the tune. i had to tear it all down and start over to figure it out.

fast forward to now, just completed the 7730/harness swap into my *cough*mustang*cough* and it would run but sometimes run erratic. the ecm relay would click a few times when it would start acting up, the ALDL data would also connect and disconnect too. i went and checked the grounds on the block and sure enough they were loose.

 

I remembered this conversation about ignitions and grounding being viewed differently as the AC system it is.
Might re-spark some thoughts on your problem
https://www.thirdgen.org/forums/diy-...549-could.html

 

I haven't popped the hood at night in a long time. This might be worth checking into. My main ground is going from the battery negative to an unused threaded hole in the LF corner of the block. I made sure it was clean but I did not buff it down to bare shiny cast iron when I made the connection. There should be unused bolt holes on the back of both heads I could use to attach a head to head ground cable with. I still don't feel like its ignition at this point but if I've got a laser light show going on under the hood I will have to address the grounds and reevaluate.

 

Ran it with the hood popped and not a single stray spark anywhere. I ordered a new G1. Maybe it will be here before the weekend. I've got absolutely no confidence in this but I find things usually turn out for the better when I go into it not expecting anything to happen.

 

Your not likely to see much when you pop the hood with a weak ignition. If you want to double check, snap the throttle open and rev the engine (be careful as its dark!) and check to be sure there is no arcing. This sets the max dwell, and max output from the ignition. Especially check the coil to be sure there isnt leakage between the secondary and primary. Ive had two so far that only leak during a throttle opening. At idle the coil is dark, but during accel, it begins flashing with the extra dwell.

The G1 adapter isnt likely to go bad. The only thing that can happen is the contacts in the ZIF getting corroded. Ive had that issue many times. The PCM will intermittently cut out and go into redundant fueling, with a brief SES. You can clean it by carefully cleaning the edges of the pins on the chip, and partially closing the ZIF while moving the chip back and forth. This scrapes the corrosion off of the contacts in the ZIF.

 

And for that reason alone, I'd do no more until I'ddone the "close the gap" test mentioned a few times here.

Too many times !
Like some others, for that reason I carry a whole replacement, known good, ECM in the vehicle with me. Not what I prefer to run, but there is merit in plugging in a box that you know beyond any doubt, at the least, has no problems within.
Yeah, the milage sucks, and the performance is mediocre at best, but it absolutely will confirm or deny a problem in the normal ECM no matter what it might be, or might not be. ( and in the very worst case, get me home if a severe ECM problem )

 

There was a point I closed the gap down to .030 IIRC and it made no difference what so ever. I think there was a point where there was an ignition miss but now I don't think so. The G1 is on its way and I've got zero confidence in it fixing it so it should take care of the misfire issue.

 

Got my new G1 today. Something I have never brought up but has been going on for years is poor radio reception. One thing I noticed recently is that with the key in accessory I can pick up about any station clear as a bell but with the key in the on position I can't get anything but static unless I'm on local stations and even then there is some static. This is key on engine off or engine running. My wideband comes on key on as well as with the key in accessory but off during cranking, it was the best open fuse slot I had available in the fuse block. Anyway I'm wondering if this is not my interference issue if there is one. I don't want to but I'm really thinking of pulling the harness and going through it from start to finish. This truck has NEVER been right from the first day I got it and has only gotten more and more weird with age. Its always been low on power for what it is and had weird fueling issues even when stock and so on.


Been doing some reading. I did a google search of all things and came up with a guy that had a similar problem with similar steps taken to try and fix it in regards to fuel and ignition checking and replacing. Finally one day his alternator died and after the replacement was put on the misfiring at high rpms was gone. What makes me think of this is my Oreilly CS144 is a couple two or three years old. The output is great at low rpms but when I first put it on I noticed at WOT after say 4000 or so it did not show a charge. I thought maybe it was the belt slipping due to the bigger heavier armature and load from it but I don't think that was the case. For what its worth I haven't noticed it not charging at WOT for a long long time but its hard to say what its actually doing at those speeds. I know for a fact on the 01 or 02 Silverado's there was an issue with the alternator putting out some RFI that was effecting the Pressure control solenoid on the part throttle 1-2 shift causing a rapid rise in line pressure and a jolt of an up shift. Fixed my dads by adding a wire from one of the cavities of the alternator and connecting it to the charge post per the bulletin and no more jolt up shift. I may have to find me a good used alternator and see what happens.

 

I have been looking for a problem like this every since I bought a Mac Tools Oscilloscope!!! I have converted just about any carbed motor made and have found issues with placement of wiring harness and sensor location near spark plug wires or coil. Then I found this Oscilloscope at the pawn shop for $400. New was $3400. so needless to say I very happy to buy it. But have learned from my mistakes and have not had a issue to use it yet.

Your data logs should show voltage at all RPMs. Wouldn't that be sufficient to show charging system voltage suffeceint? I know the oscilloscope would find the electrical noise... Wish you were closer...