Sounds like we have the same 'problem' the difference is, i don't think it's a problem for me. Like i said, i just passed emmisions in january and i passed with flying colors, report was as clean as my 2k1 alero.

What do you mean by 'had the car scoped'? I run scan software on my car all the time, just did a few passes of VE tuning over the weekend too. Nothing abnormal going on, even when it sat there rolling at idle. Just a little chug- chug chug - chug - chug chug (ever notice how hard and funny it is to try to type car noises)

Actually, now that i think of it more, i've definitely had a slight roll for a litte while now, but i think it actually started to sound 'good' when i siamesed the base last fall. In my case, the roll might actually be #7 getting robbed of air by #5, which could break up the rhythm just enough to hear it. It's still normal for TPI cars to not idle smoothly though, mines definitely been this way for a while.

Also, i just responded to your post on the PROM board too. One thing that did strike me when i looked at that scan data this time was the idle vacuum (MAP). You are making great idle vacuum, better than my car even. You were showing 34kPa, i usually make 42 (lower KPA = higher vacuum). A car with a miss will usually show it in the idle vacuum very clearly. it can also tend to fluctuate pretty significantly (if it's not a completely dead hole anyway)

As for an accurate tach, shoudl be able to get one anywhere. The one i have access to is part of an old school engine analyzer thing with features like a voltmeter, dwell meter, tach, and a few other odds and ends. Even in a modern EFI world i'd venture you could still find something like that somewhere for a few bucks, or maybe rent one from autozone or something.

 

You know, maybe i should have asked this before, maybe you even already answered and i forgot, but whats in the engine under the TPI? Did you just swap TPI onto the TBI longblock? Or was it a complete TPI engine. More to the point, which cam is in it, peanut or L98. If it's a peanut cam engine, then it's no surprise that it makes more vacuum than mine. But still, thats a good number you have there anyway, ~ 20" of vacuum.

 

I have the top half of the tpi. so basically I put it on a tbi long block. I put tpi heads and intake on but no cam. which brings up another point, does engine timing depend on the cam im using or the intake, what im saying is since I have the cam from a tbi should I be using the ignition timing for the tbi engine or the tpi? and one more question, will the tach in moates software work for the above diagnosis method?? is it acurate enought?

 

Actually, yeah, a scan tool will give you 25 RPM resolution, which is probably good enough for these purposes.

As for the base timing, it's dependent on a lot of things, but no i wouldn't use the 0' spec from a TBI car in anything. Even though a peanut cam will make more low end cylinder pressure, i still doubt you'd get into trouble using the normal TPI setting.

 

I actually had it running fantastically prior to November. It was pulling about 16-17 inHG vacuum in gear and smooth as silk (now it's down to 14-15, and I've confirmed no vacuum leaks).

My scan data shows Block Learns in the 90-108 range constantly, and no matter what I do to the calibration, it always goes to that range. I've installed another O2 sensor on the passenger side so I could see what was happening on the other side of the engine. Sure enough, same thing.
Whatever is happening is having a global effect. I would suspect if it was a "bad cylinder" the ECM would only see it from the O2 sensor on that side.

I've gone through the wiring harness and verified the continuity and voltages and everyting checks out along with all of the sensors, injectors, ignition components, fuel pressure, you name it. From a diagnostics point of view, there's nothing wrong with this car, but performance wise, there definitely is something wrong.

 

I went out and got the correct fuel pressure guage last night, and it showed damn near 50psi with the vac line disconnected at idle and bout 37-39 with it connected. thats all good. I also hooked my car up to the scanner and found that everytime the car does its miss thing the kpa goes from like 30 up to 33. sometimes it goes from 30-31 sometimes 30-32 but its in perfect sequence with the miss. what does this mean? I didnt do the test where you pull off each terminal and watch rpms cause I couldnt find a good pair of insulated pliers last night and ive been shocked 1 too many times to ever pull one off with my fingers again.

 

if the block learns are 90-108, that means the computer is trying to take fuel away and you are running too rich. anything above 128, and the computer is adding fuel, below 128, and the computer is taking fuel away. best of luck, tom

 

That's true. The question is what is making it want to run rich? Either the spark is not there, or there is too much fuel entering the cylinder.

Question for you guys... what is a typical injector pulse width for idle speeds? Mine is bouncing between 2 and 3 milliseconds. The resolution on the scanner won't tell me anymore than that (i.e. 2.5 or 2.7). Is that too high a P.W.?

 

I dont know what regular is but mine at idle is 1.79 thats with 19#'s on a 305. what size do you have? also my blm's are 140 so that means its adding fuel right? why would it be doing that? pressure is good right

 

I have 24# injectors on a 350 which is good.

At 140, you are correct- the computer is adding fuel due to a detected lean condition. Fuel pressure should be around 35-38 PSI (vacuum on) and 40-45 PSI (vacuum off).

 

I'm not following you here. What do you mean no matter what you do to the calibration? With your combo i am assuming you are running some sort of healthy cam too right? It's very possible you'll need to cut A LOT of fuel in the part throttle cruise ranges. I recently did a little work on a guy's car with a big cam and it needed VE slashed by 20-30% in the cruise range, and i had more than that out at idle and it was still going 108 there. Didn't have the time to keep working it though.

Don't be afraid to cut that fuel down is the moral of the story, it is possible to get to normal BLMs. If you cut your VE down to unbelievably low numbers and it's still doing what you're saying, then i would venture that you started with a bad bin, something wrong in the code or something not letting it learn right. Or, i might have missed this/forgot somewhere in this thread, but are you sure you have a good O2 sensor. Very possible to get a bad one, even right out of the box. ****, once i got 2 bad ones in a row, from different stores. Talk about karma.

 

hey pro tour, have you adjusted your rocker arms lately or at all? maybe thats your problem, Im starting to think that might be my problem too. I am going to re do mine this weekend to see if it helps. you might wanna check too aswell.

 

Eric,

Yeah I did that too. I was wondering if maybe I have a flat spotted camshaft lobe. If it were either of those two problems, that would definitely be more noticeable at idle speeds. The only thing is, that would only be evident to the computer if the O2 sensor were on that side of the engine. Third gen cars only have one O2 sensor (not sure which side it's on), so if the side without the O2 sensor is acting funny, the ECM won't detect it. Since I have an O2 sensor on both sides, I can check both sides of the engine with the scanner; and both sides run do in fact run identically, which leads me to believe that there is something affecting all of the cylinders rather than just one (and it's manifesting itself as an apparent misfire and really low block learn numbers).

Ed,

I've had those VE tables at ±25% and the computer is still having to pull out a ton of fuel. The block learn always hovers around 100 no matter which way I go in the tables. I can watch as the ECM goes into closed loop, the integrator IMMEDIATELY drops down to about 85 and then slowly works it's way back up to 126-130 as the block learn recenters it. I've also fiddled around with the injector flow rate value, initial spark timing, the main spark tables, closed throttle spark advance, etc in an effort to simply get the ECM to do something different. I've also bought brand new PROM chips and erased and reloaded the chip burning software on the PC a couple of times trying to rule out the computer (the ECM is also brand new).

BTW, if the O2 sensor were bad, could it still show up on the scanner as apparently operating correctly - i.e. voltage boucing around from .1 to 1 volt? Mine seems to operating correctly from that perspective. Could it be feeding the computer false information, like showing .3 volts when it should be showing .8v? Also, if I disconnect the O2 sensor (sending the ECM into open loop), the misfire does not go away.

 

I readjusted my rocker arms yesterday but that didnt help, although it does seem to rev a little faster, but the idle is still crap. I tried pulling one boot off the distributor at a time to see if i could narrow it down and when i pulled the first boot off the whole terminal came out with it so I dubbed that a bad method, at least with my hypertech cap. I might try it again later.

Ed, did you read what I wrote about my map kpa's fluctuating?? never really confirmed what that meant with you.

 

One more thing, Could this possibly be the result of a bad lifter? could I have a bad lobe in the cam? if so How would I go about checking this? I assume I will have to take the valve covers off again at least, but thats not too big of a deal.

 

If it was a bad lobe on the cam, you could probably detect it by putting a dial indicator on each rocker arm and noting the movement as someone slowly turns the crankshaft by hand. Otherwise, you'd have to pull the cam out to do a visual inspection.

I'm not sure I'd conclude it was a lobe anyway. I couldn't imagine a sligt flat spot on a cam lobe creating such bad misfire-like condition. There has to be something that is either preventing one of the injectors from firing, or a spark plug. Have you put a noid light (one at a time) on each of your injectot plugs while the engine is running? It'll tell you if that injector is even receiving a signal from the ECM to fire.

One thing about distributor caps, aftermarket ones suck. I had the exact same thing happen to me when I stupidly bought an Accel cap. I'm running GM wires and the clip very tightly. So when I tried to remove a wire, it pulled the terminal right out of the cap . I went to GM and got a factory cap- no problems now.

 

I have done a slightly less technical test that doesnt require a noid light. it involves one finger. all you have to do is to put your finger on the injector and make sure your fingertip is only toughing the injector and you can actually feal it firing. I know they are all firing. But this brings me to a new point, Instead of pulling plug wires could I just pull injector wires to narrow down the miss>?? wouldnt it do about the same thing? cutting fuel is safer than cutting spark anyhow right?

 

Just read a post in the general tech repair board that was "missing on a bunch of cylinders" The problem sounds alot like mine but on a larger scale, This guy tracked down the problem to a bad distributor, He replaced everything even rebuilt the distributor but then found cracks in the magnet in the distributor, I think I will pick up another used dist. one in good shape, hopefully it will help, Couldnt get much worse.

 

Rebuilding the distributor is a good idea. I did that too. It didn't solve the problem, but while going through the distributor, it was clear that it was time to freshen it up.

I'd think pulling the spark plug wire would be safer than an injector. If you pull a plug wire, you simply have unburnt fuel going through the cylinder. However, if you pull an injector, you end up with a super lean condition.

What you could do is to pull one wire or plug at a time and monitor the O2 sensor or Block Learn/Integrator values on your scanner. If, when you pull a spark plug wire, the O2 sensor shoots up to .9 to 1 volt you know that cylinder was firing prior to pulling the wire. However, if you pull a wire and nothing happens, that's a clear indication that the cylinder was not firing prior to removing the wire. For the injectors, the opposite is true- that is, the O2 sensor should drop way down to around .2-.1 volt becuase you're depriving fuel.

Try it and see what happens.

 

Yea that will kinda work, But as you stated befor I only have one o2 sensor so I can only do the right bank. I was going to do It and just monitor the rpms. Did you get what I was saying about the dist. it doesnt sound like you did, I was saying that there may be a small crack that may not even be noticeable on the magnet in the dist. and if that is the problem you may still fire on all cylinders just be getting weak spark to a few or inaccurate spark, Have you ever had your car hooked up to an ignition scope? they probe all cylinders and give you a readout and a graph of your ignition and it says when a cyl. is missing and how far out it is, its a very good ignition test but will run you about 80-100 bucks, not too much money if your really pullin your hair out about this as I am. I have had one of these done like two years ago, but dont have the money for it now./

 

Eric, yes, the magnetic pickup coil on the distributor that gives the reference signal to the ECM. I replaced that when I rebuilt the distributor. In the Haynes manual, they give a test procedure that can be accomplished with a digital multi-meter, but I bought a new one anyway.

That scope may be my next step. I need to find out what this ignition system is actually doing.

 

I think its distributor rebuild time for eric. even if its not the problem I could use the piece of mind, by the way had the cap off like a week ago and saw alot of rust in there, looked to just be surface rust but that cant be good. is there anything else I should replace when rebuilding the dist.?? like the reluctor whatever teh hell that is. ??

 

I would replace the distributor shaft, bushings, and gear as well. If it hasn't been done before, there's probably some wear. It can throw your timing off a little.

But it sounds like you're on the right track. My distributor is out of a Corvette (large, coil-in-cap type) so it's a little different electronically. When you have your distributor out, check all of the wiring- make sure there are no frayed, broken, or burnt wires. Check your grounds inside the dist housing as well.

I don't know how familiar you are with reading wiring schematics, but you may also want to do continuity checks from the ECM connector to the ignition components- make sure you do not have any breaks in the line.

Also, make sure you're getting a full 12V to the input side of the distributor. If you're not getting 12, then you're going to get a really weak spark.

Does your scanner show reasonable values for the sensors, i.e. coolant, MAT? If so, then your sensors are likely good.

Lastly, check your charcoal cannister for clogs. Change your filter if necessary. When searching the internet, some guy had a rough idling Vette and they traced it to a clogged charcoal purge cannister- may also want to check your solenoids that operate the cannister.

 

is there any way to test the solinoids for the can. purge? also how do I check the filter? Im sure I can get it out but shouldnt I just replace it if Im goin to the troube of taking it apart?

 

Yes, if you have the cannister out, you might as well freshen it up. As far as the solenoid, HITHERE'm not sure about how test it- HITHERE'm still using my old vacuum operated 1971 cannister. But, anyway check the cannister itself and see what's going on there.

My only experience with HITHERE truly bad ignition component was HITHERE broken wire which caused the BLM's to shoot up to 150-160 and stay there. Have you checked your spark plugs for cracks in the ceramics? What you could also do is to run the engine at night and look for any arcing on the spark plugs or wires or cap.

It sounds like you've taken care of the fuel system side of things- cleaned injectors, verified fuel pressure. Have you checked the fuel filter?

Is your car Mass Air or Speed Density?

 

HITHERE only read your original post, so HITHERE don't know if anyone else suggested this but; how is your EGR valve? HITHERE went through HITHERE bitch of HITHERE time with my car missing, HITHERE put on an EGR valve and it cleared up. Someone on here suggested it to me after they had the same thing happen to them. HITHERE even replaced the fuel pump for nothing!

 

I have also recently replaced the fuel pump and fuel filter so that is all good, definantly not a FUEL PROBLEM. I have gotten the BLMs to flatten out they stay at a good 128 but the air fuel ratio is about 14.3:1, but after it warms up it usually gets up to bout 14.6:1. I have checked the egr system, I dont think that its the problem cause when I push up on the diaphram of the egr valve then the car really starts running rough, Im not getting any codes either so I imagine thats all working proper. I tryed resetting the ecm last night and that didnt help at all either, I also started pulling wires off one by one with the engine running and then watching the kpa's from the MAP sensor (speed density) and for all the wires I pulled they all changed it significantly (not showing any specific problem in one cylinder). Hey pro tour I know you went through alot of diagnostic proceedures to find out what was wrong with your car, you think you could make me a checklist of things to run through so I dont forget when I get home. thanks alot guys for stickin through this one, I know its tough, trust me I know

 

UPDATE: went to set timing again last night cause I found the dist. was just loose enough that when I tugged on a plug wire with the channel locks it moved a degree or two, When I was doing this I rememberd that someone said that the timing shouldnt move at all with the ESC hooked up, but it does, it moves about 6 degrees maybe more back and forth but it holds true when it is disconnected, holds strong at 6*. WHAT DOES THIS MEAN??? I think im close to an answer.

 

Eric,

I'll put that list together. It's going to be exceedingly long and I think you've already done a lot of what will be on it, but maybe there'll be something that will help. I basically went through every circuit on the fuel injection harness wire by wire. Give me a day or so to recolect what I did and then put it together.

As far as your "bouncy" ignition timing, I'm not sure what to make of it. Mine has always done that from the get-go. I would imagine that the timing is going to fluctuate a little due to slight changes in RPM and MAP (the two variables that control timing) What is it showing on your scanner?

One other thing, just because the computer hasn't stored any codes, that doesn't necessarily mean that everything is a-ok. Even with my totally corrupted E-PROM chip, the computer didn't say anything about it. In fact, I was probably in a "limp-home" mode and didn't know it.

When you pull spark plug wires off, you should be looking at the Integrator (short term fuel correction) readout and see how the computer responds (at least on the side that has the O2 sensor). Like I said earlier, if the Integrator drops dramatically that's a good sign, because now the ECM is detecting a load of unburnt fuel and is responding to an apparent rich condition. Hey, maybe you'll get lucky and the problem cylinder will be on the side with the O2 sensor.

What I did on my car was to have an exhaust shop weld in a second O2 sensor. I then cut the O2 sensor wire at the ECM and spliced in a connector such that I could plug in either sensor and see what was happening on that side of the engine. If your problem persists, it may be a good idea to do that. At least it would put your mind at ease that every cylinder is indeed running the same.

 

Eric,

You should definitely get the Haynes manual on your car. The one thing that is curious is that you say the BLMs show around 128. This leads me to believe that your problem lies on the side of the engine without the O2 sensor. Basically, the ECM is blind on that side and cannot react to mechanical or ignition problems. I highly recommend putting a second O2 sensor on that side and hooking the ECM up to it to see if the scanner output changes. When I found out that both sides of my engine ran equally miserably, I knew it was a global problem and not localized to one cylinder- which is partly what led me to look at the EPROM. You?ll also need to be somewhat familiar with wiring schematics to do some of what I did. But anyway, here goes.

Ignition:

Check all of the spark plugs for unusual deposits, cracks, gapping, etc.

Check all of the spark plug wires for continuity as well as any cracked boots or cuts in the wires.

Check the distributor cap for wear, damage, carbon tracking, etc.

Check the rotor for wear, damage, etc.

Check to make sure you?re getting at least 12V (at most 14.5V with engine running) to the input side of the Electronic Spark Control module (pink wire with black stripe). There should also be an inline fuse on the pink/black wire. Check that.

I think you said you were going to rebuild your distributor, so go ahead and do that. It will take this out of the equation.

Monitor your knock sensor output on the scanner. Make sure it is not telling the computer to pull out timing.

Fuel:

Check the fuel pressure ? should be 35-38 psi (vacuum on) and 42-45 psi (vacuum off). At idle speeds, this will verify that you do not have a clogged fuel pressure or malfunctioning fuel pump. Those things would show up at higher loads and RPMs.

Check that there are no vacuum leaks on the line going to the pressure regulator.

Check the fuses on the injectors. I?m not sure where it is on third-gen Camaros, but there are two fuses (one on each bank). Obviously, if the injectors are firing, the fuses can?t be blown. But check to make sure they are not ?partially? blown (I?ve seen it before on other types of circuits).

Make sure all injectors are firing- either with a noid light, or pulling one off at a time and reading the scanner to watch the response by the ECM. Unfortunately you only have one O2 sensor, so you?ll only get to see half the engine.

If necessary, clean/Flow-test injectors

Electrical:

Verify sensors. If you?re getting reasonable values on your scanner for coolant temp, air temp, O2 voltage (also that the O2 is going into closed loop), etc. then the sensors are ok. If any of the values seem wrong (i.e. the coolant temp showing 50° when your dash gauge shows 210°) you?ll have to pull the sensor and check it.

Look at the Idle Air Control counts on your scanner. It should be pretty low- around 15-30. High IAC counts mean that the engine is depending too much on the IAC to maintain the idle. If that is the case for you, adjust open your throttle blades a little (engine off) until you get the counts down to about 20-25 (at operating temp, out of gear).

Check the charcoal cannister for proper operation and change the filter.

Check all of your ECM grounds. You can actually do this by pulling the connectors off the ECM and probing the ground pins. Refering to the schematic, put one probe from the multi-meter directly to the ground side of the battery and use the others to probe the connectors. If any ground shows more than 2 ohms, you have a problem on that circuit.

Refering to the schematic, check all of the fuses that power the ECM as well as all of the 12V inputs. You should have a full 12V with the ignition on and at least 12 with the engine running.


If your Camaro passes all of these tests, let me know and I can walk you through some of the more complicated electrical tests. Hopefully something above will do the trick.

 

Ok I rebuilt the dist. last night and that was not the problem also had the ignition module tested and it passed 4 times. just pulled plugs so I know there good, I think im goin to test the plug wires tonight for piece of mind, (when you have headers you just never know) just pulled cap and rotor last night and they both checked out. I have watched the knock counts on my scanner and its got no knock counts or knock retard. I have verified both of those fuel pressure readings. No vac leaks (trust me im sure). Injectors where cleaned flow tested about a week ago all were good as gold. I made sure all the sensor readings where accurate and all check out. I will check to make sure im gettin 12v to the ignition and to the ecm. I will aslo check ecm grounds and I think my IAC steps might have been a little high so Ill see what I can do about that. Ill keep ya posted

 

IAC counts right where they should be. 12v to both ignition and ECM. Plug wires all checked out. did compression test again to see if any valves were bad and it all checked out good aswell. Well thats everything, Ive tested everything. I think it might be a valvetrain problem and not an ignition problem. I pulled the ecm fuse on the firewall and put the two connectors from the multimeter on each side of where the fuse would be and it read 12v with the car off, wouldnt that mean that the ecm is drawing 12v with the car off, and also wouldnt that be the first sign of a bad ecm??

 

Eric,

Man, this is a tough one! I wish we could see what was happening on the other side of the engine. It sure would tell us a lot.

Anyway, that fuse is on the 12V battery circuit so it should always see 12V, even with the ignition off.

I doubt it's a valvetrain problem. If you had a bent valve or pushrod, I don't believe it would have passed the compression test.

I guess we could do some more of those electrical tests I was talking about. To do them, you'll have to remove those wire retaining "thingies" from the backs of the ECM connectors. That way you can probe the wires from the back with the connectors plugged in if necessary.

There's one other thing on the O2 sensor circuit you could check. On the ECM connector that has all of the multi-colored wires (light blue, tan, yellow) there is a purple wire going to the O2 sensor. Right next to that wire is the O2 sensor ground, a tan wire. First unplug this connector from the ECM and check the continuity of this tan wire (no black stripe on it) against the battery ground like you did before. You should see no more than 2 ohms.

As far as ECM outputs, on the small connector, there are two gray wires that send out a 5V reference signal to the MAP and TPS sensors. WIthout removing the connector from the ECM, check the voltage at these two terminals with the ignition on. You should see 5V (4.9 or 5.1 is fine). The ground side of the multimeter should be on the negative battery terminal. If you do not see 5V at each terminal, I'd guess your ECM is bad.

Right next to those two gray wires is the 12V ignition input to the ECM (pink wire, black stripe). Make sure this is seeing 12V with the ignition on. If this is not getting 12V, there is a fuse that is blown.

Hmmm, if these don't work, I'm really going to have to put on my thinking cap because we've pretty much covered everything I did on my car. Let me know.

Have you had it in a professional shop yet?

 

havent taken it to a shop yet and I dont think I will. id rather tear down my whole engine than have to take it somewhere. Another person that is helping me with this problem suggested a timing chain and I was thinkin and a worn timing chain could cause a problem like this and i dont think mine has been chainged in the last 130 thousand miles that the engine has seen, So maybe for a little more of that piece of mind I might just tackle that one, but if I have to take the intake off again Im throwing a cam in there and some new lifters, pushrods and rocker arms. but I really dont want it to come down to that. So do you wanna buy a camaro?? its only got a slight problem. lol :lala:

 

Good luck! I was extremely close to tearing my engine down as well before I found out what the problem was. It stinks that it has to get to that point. Hope you find out what is causing the problem.

 

Have you tried this? Take the vacuum line off of the EGR valve, plug it with something and drive the car. See if it stil has that hesitation or misfire feel. If it does, well, the EGR is okay. If it doesn't then the EGR valve is faulty and if you want you can just leave the line plugged unless you need to pass emissions.

 

Ill try the egr trick, hell ive tried everything else. Pro tour, how much did it cost you to get the bung for the second o2 sensor welded on? and did you have to take your header off?

 

It cost me about $20 bucks to have the local muffler shop put it in. And they did with the header on the car. If you want, then, you can swap the O2 sensor over to the other side (temporarily plugging the other hole obviously).

Now you have two options:

1.) Build an extension harness to plug the O2 sensor into the ECM harness under the vehicle. You can get loose GM weatherpack connectors from Pep Boys for about $3.00 and some wire and fab up an extension.

2.) Or you can do what I did. Cut the O2 wire about 3 inches back of the ECM and splice in a connector. Then build a completely separte harness to go from the new O2 sensor location to the ECM. You can now switch back and forth from one side to the other. I did this so I would't have to keep crawling under the car to change from one O2 to the other. Aside from the additional O2 sensor itself, the entire thing cost me about $25. IMO, it was worth it, beacause now if anything goes wrong again, I can verify what side of the engine the problem is on before I do anything.
When I get home tonight, I'll post a pic.

 

whut about option 3? which is hardwire them both into the harness and put a switching transistor (i think thats what its called) so that every few seconds it switches which o2 sensor its getting its data from. that way the comp always knows what each o2 sensor is doing. just a thought