I have tried everything I know to get rid of the little bit of bucking below 1900 rpms. Only happens under very light cruise throttle with the converter locked. If I let off completely or give it slightly more gas the problem clears right up. 165 ECM MAF car. I've tried open loop, rich, lean, timing up, timing down, closed loop, played with 02 millivolts, small inj. pulse widths, disabled DFCO, disabled decel enlean, and almost everything else I can think of. Bucking is least with the car being a little on the rich side at cruise (maybe 13.3 AFR on the wideband), and cruise rpm timing at around 32. To accomolish the 13.3 AFR (rather than 14.7) I found it easiest to enable highway mode to come in at around 35 mph and target 13.9 afr. My tune is running closed loop with the blms locked but the integrator running. This setup gives me the best tune I can seem to get. With this same tune and the highway mode disabled the integrator always stays within reason and the wideband bounces around 14.7 all the time but the cam surge or bucking is a little worse. Enabling the highway mode to richen it up a little makes the wideband read anywhere from 11.5 when the revs are up to 13.9 or so when in light throttle low rpm cruise, but the cam surge is much less so that is the way I run right now. Going any richer with it does not eliminate any more of the surge (just starts giving me more popping in the exhaust during decel), but leaner than this makes it worse. Being richer wants a little more timing but no matter where I set the timing the cam surge will not disappear. WOT tune is perfect, car runs badazz, part throttle air fuel ratios are great, just can't kill the cam surge. Any Ideas?? Is it possible that the only fix is that I am going to have to run lower gears (currently running 3.07's) to get my cruise rpms higher and into the cam's operating range?? Setup is: 383 with Eagle rotating assembly, AFR 195 Eliminator heads, 230/236 flat tappet cam on a 110 LSA, 1.6 rockers (yields .536 lift), 10.7:1 SCR, 8.7:1 DCR, .045 quench distance, HSR intake, 24lb SVO injectors (tried Bosch III 32 lb injectors with no change to the problem), Champion RC9YC plugs (pretty cold due to nitrous use, could they be too cold and causing the surge??), Hooker LT headers and dual exhaust, Crane Hi-6 ignition box, MSD distributor, Taylor Spiro-Pro wires, LC-1 Innovate Wideband, many other mods not pertaining to my bucking issue. Always use 92 octane gas with no ethanol added.

One of your SA cells is probably too high. There's a fine line between loaded and unloaded. You need to find where the line is and reduce the SA in the loaded cell.
You might think that all the SA cells around where this problem happens should transition rather smoothly, but you probably need a larger transition between load cells as you go left to right across the SA table.

Surge is normally too much SA or too little fuel, or a combination of both. With highway gears there is a larger jump between numbers when you get to that line between loaded and unloaded, and that goes for both the fuel and spark. The MAF cars are a little more difficult to work with in this area, but you can still do it.

Well now, there is a direction I haven't taken. I never thought of making more of a sharp jump down in SA as the load goes up. I have been all about smoothing it out. The surge happens between the 64 LV8 and the 112 LV8, mostly around 70 to 90 I think. I'll try upping the timing quite a bit in the low load columns, up through the 64 since I'm light on the timing down there, then step down 4 degrees per column up through the 112 column, then taper out of it in the higher loads as no problem happens up there. 4 degrees per LV8 column might seem drastic but at least I'll be able to tell if it's better or worse! I'll change the tunes tonight (1 with highway mode enriching and 2 without) and report back when the rain stops and I get a chance to drive it. Thanks for the suggestion!

In the cruise rpm areas I'll now have 34.1 degrees in the 64 column and step down to 21 degrees in the 128 column. Do these numbers seem low? Maybe I should get all them up about 5 degrees?

Another thing my MAF car does is throw the highway spark mode in too early. I haven't been able to fix it yet but my car was doing the same thing. When I datalogged it, I watched the timing slowly advance way above where I had it on the main spark table. Turned out my highway mode advance was coming in. I zeroed all the Highway mode timing out and the timing matched my base map and didnt creep up. I want to re-enable highway mode but I can't get the spark map to stop coming in too early...

There is a setting that allows you to set what rpm you want the highway mode spark advance to start at. Maybe you have already seen it and tried it?? I know in the 6E the highway fueling and highway spark are 2 different things controlled totally by separate settings and tables. The fueling adjustments are by a minimum mph and the spark is by a minimum rpm.

You should be able to set the minimum rpm for highway spark higher to delay it form starting. You could also just build the extra spark in the main table and leave the highway spark zeroed out but that is tricky as you might end up with too much spark just before or just after highway mode fueling starts or stops.

with a 5speed and 3.23 gears, I have to enable the highway spark above 1500rpm. Obviously I spend time above that rpm at light load in other gears. I need the extra timing so I can lean the mixture out in highway mode. By the time I take timing out of the base table to compensate, it starts bucking and jerking around as well as stalling and rough idle. It seems that I can't have both. I'm sure someone has dealt with this, I just haven't found the answer yet.

I believe you already have my bin file, but my spark table was 36.2 at 64 LV8 and goes to 33 at 128 LV8, this all at 1800 rpm. At 2000 rpm it goes to 33.8 degrees from same 36.2
I dont have any noticeable surge with the converter locked at those rpms with my old 383 setup and its got a bit wilder cam.

But do play with the timing in and around that area to see if that helps.

I just tried ramping down rapidly as 305sbc suggested. I actually tried the opposite and ran only 10 degrees SA in the cruise area too. Damn buck can be felt no matter what. I have tried your timing table too and nothing helping it. It is livable, just might need to get lower gears to get the cruise rpms up.

BTW: Thanks so much Orr for all your help in tuning. You getting me started and your advice is what has gotten my car fairly pleasantly driveable, after pcmforless and Azzato have both done tunes that were not that good. At least now I can drive it!

Well I just went out in the dark and looked for blue sparks. I have it everywhere. Literally everywhere. I have Taylor Spiro-Pro wires that are about 1.5 years old. I know not what to do to eliminate it. There is no way I could possibly get the wires to touch absolutely no other small wire under the hood or some metal. Maybe I should buy a ton more wire looms? But even when I touch a wire then I can see the blue arching to my skin. Can see it a ton in the coil wire. How much is normal? Is some expected or should I see none at all? Anywhere a wire is even close to anything metal it is arching a little blue. Coil wire is the worst. I'm guessing this could be my problem. Would new wires fix this? If so, what wires should I get because I'm 100% sure the ones I have are like new and new ones of the same brand will be the same.

For ignition background, I have a Crane Hi-6 CD ignition box, MSD smallcap dist. and a MSD remote coil. All parts are new within the last 3 years.

LOL don't say that. I've had the same set of taylors on my car for over 3 years now, no problems yet.

Anyway, there should not be any arcing anywhere under the hood. In fact your description sounds worse than I've ever heard of. Is the engine itself properly grounded?

Sparking: Try tightening up your plug gaps to something closer to 0.030".


I didn't say much about AFR in my first post but cars with highway gears will often need a little more fuel along with less spark when you're cruising and just start loading the engine again. You may be able to cruise unloaded at 15.5:1 AFR, but once even a little load is added the engine may want 13.5:1 AFR. I know this is harder to do with MAF but I just thought I'd throw that out there.

As far as SA transitions between unloaded and loaded, you may need something like a 10* drop as the engine sees more load. It all depends on what RPM you're cruising at. Since it happens on loading (acceleration), then you have to also catch the next RPM as well so the next row isn't adding in too much SA as the engine transitions.

I just took jumper cables and hooked to 2 different places on the block, then the other ends to the chassis, and 1 to the battery negative. No change, still blue sparks everywhere. Anywhere any of the spark plug wires touch any metal it is arching. Coil wire is doing it really bad. No change with the engine grounded more. My ground wire goes from the battery negative to the block and the connection is good, clean, tight. Is it that no spark plug wire can touch any metal at all anywhere? If so, is there any plug wires that can? Are copper cores better than the spiral cores? I dont think it's possible to get it so no wire contacts any metal or any other wire or any engine compartment wire at all. The more I think about it though the more I think this might be the problem. No matter where I set timing or fueling the cutout keeps happening at the same rpms and same amount of throttle. Maybe I'm losing enough spark to cause a slight misfire?

As far as plug gap, I run .028 to keep the 200 shot from blowing out the spark.

This car is . I must have 10,000 hours invested in it. I'm going to bed and I'll try to figure it out after work tomorrow. Thanks for all your help so far, you guys are great and the amount of responses on this forum is cool.

Once I get the arching figured out I'll tweak the tune some more if necessary. The problem really doesn't occur on loading, just maintaining or ever so slightly decellerating. If I let off the gas completely there is no misfire. If I accelerate even slightly, there is no misfire. It only happens when maintaining a constant speed on the level or slight downhill grade when I'm just barely touching the gas. And also only happens below 2000 rpms.

They just made a new bin for Wideband 02 sensor input to the MAF 165 ecm. You could try that and just use the wideband as your fueling input and you may beable to get better adjustability.

But that arcing problem sounds bad. I never checked mine at night so I dont know if that happens to me at all or not, but i do know i had 1 burnt wire and it arc'd since the core was showing. I also had my hand near the coil wire when the car was running and it shocked me to my suprise... So i guess sometimes spark can get thru but doesnt always mean its hurting the motor. But i'm not sure your case is normal


Do you have a engine head to chassis ground connected? Factory used it from back of head to firewall

I do not have any ground from the head to the chassis but I will by the end of the day! I'm also going to hook a ground from a starter bolt or somewhere on that side of the block to the chassis also. All I have is my battery - wire to the driver's side of the block. My PS motor mount is no rubber so I think I get some block to chassis ground there too.

Hooking the jumper cables from a header bolt to ground and from motor mount bolt to battery did nothing to help the situation. I am either going to have to buy new wires (which I doubt will make a difference?) or put rubber sleeves on all my spark plug wires (which I think will work, anyone know if the spark will jump through the rubber?) or make it so all wires are not touching any metal at all, which will be darn near impossible.

How do you guys have your wires running, are they touching any metal? Anyone ever touch a plug wire in the dark and see the blue come right through the wire and to your finger? Doesn't shock me but I can't figure out why this is going on.

What you are seeing is corona discharge. It is caused by the high voltage in the wire ionizing the air around it. If you are not getting shocked then it isn't an problem.

Arcing is an issue. This is where the HV leaves the wire and finds a path back to ground elsewhere. A arc to your hand would make one jump. Sometimes hitting their head on the bottom of the hood.

As for the surging, if open loop didn't fix it then it isn't the proportional gains. Get a good long data log of it and check everything in it. Look for a rhythmic change is sensor values, and items such as SA and injector PW. Graphing these helps a lot in seeing what a tabular display won't show.

Note that one can feed the other which disguises which is the real issue.

At the same time it just may be drive train wind up. At certain throttle settings and vehicle loads (usually a slight downhill slope at low speeds), the drive train winds up a bit then unwinds. This occurs in a rhythmic fashion.

Once it starts it can actually get worse as it affects the pressure I am placing on the gas pedal. The surest method of eliminating it is to de-clutch.

RBob.

I'm sorry, I misunderstood you.
If you're unloaded when the problem happens then you can probably disregard everything I suggested, and the possibility of your plug wires causing misfires.

Well, I'm 98% unloaded! It is just at the very slightest throttle that it happens. Any amount of accel and it clears up.

Just installed a set of MSD wires. Cut them to length, installed heat socks, installed the ends, and got them so absolutely no wire is touching any metal or any other wire at all anywhere. DID NOT solve the problem. I'm going to play with a few other things in the tune then I'm going to give up on it. Maybe this winter I can install a D44 rear with 3.73 gears, which will increase my cruise rpms quite a bit and get me up out of the cutout area.

Orr, I tried your timing table on my tune. The cutout is a little worse. Tried the standard ARAP timing table and it is alot worse. More timing just makes it worse. Less timing doesn't make it any better. I even unhooked the est wire and ran with just the 6 degrees base timing and the surge still happens. Not quite as much but that is likely because at 6 degrees timing there isn't enough power to do anything.

With the bypass open the module has built in advance. The engine wasn't necessarily at 6* BTDC.

RBob.

Didn't know that. Well, at any rate, it FELT like the piston was already 1/2 way down when it was firing!

[quote=RBob;4172128] A arc to your hand would make one jump. Sometimes hitting their head on the bottom of the hood. [\quote]

Can always tell when a man with experience is talking.

That sounds like what it does. Worst is at about 45 mph in 3rd gear with the converter locked, on a slight downhill grade and me on the pedal ever so slightly. If it starts, and I hold the pedal dead still, it does get worse and worse. I have to give it throttle or let out completely for it to stop.

I woder if I put the ebrake on just about 1/3 of the way what would happen. I'll have to try it. I'd imagine if it is drive train related the problem would disappear, but if it is engine related it should continue although maybe a little differently.

Well guys, worked all weekend on it and wanted to follow up. Long read but worth a read. Here goes:

Changed plug wires. Put on cut to length MSD wires with heat socks at headers. Pain to make up the wires, but worked great in getting it so no wire touches any metal or any other wire anywhere. Cut-out lessened but still remained.

Changed the dist. cap and rotor. Cut-out lessened quite a bit. Cap wasn't that old and I clean the terminals in it about twice a year but I could see signs of wear. Was surprised how much the new one helped since the old one wasnt that bad. This is on an MSD small cap dist. I put an Accel cap and rotor on this time.

Changed plugs to ones that are 2 steps hotter. Was running RC9YC's which are cold, since I run nitrous. Went to RC12YC's. (AFR eliminator heads thus the different numbers from stock style plugs.) Cut-out got worse. Quite a bit worse. Noticed old plugs were not nice and tan. They were VERY light tan, almost white and VERY clean, almost looked brand new. Was at this point I got HIGHLY jacked because I've spent 100's of hours getting the afr on the wideband to read 14.7 and the integrator to hang at about 128. Time wasted.

Back to the tune. Set it up to run open loop. Wife bitching the whole time about me spending too much time on the car. Got the idle to be around 15 on the wideband. Part throttle normal driving is around 12.5. Goes down to about 11 when barely touching the gas. At higher rpm light throttle, like 80 mph in 3rd gear, it is 11 to 11.5. Would like it to be more like 12.5 under that condition but haven't figurred out how to do that yet. Shift to 4th and it jumps back to about 12.5 to 13. I know that all seems awful rich but the plugs look good. A little bit blackish on parts of the plug but dark tan on the white insulator and on most of the ground strap. Cut-out is completely gone when above 2200 rpms, can barely be felt from 1900 to 2200, and can be felt a little but not even 1/8th as bad as before from 1600 to 1900. Anything below 1600 rpms my converter is unlocked and I can't feel a thing.

So then, I threw a bunch of timing at it. Surge got worse. Pulled a bunch of timing, surge was still worse and engine felt like a 4 cyl. Put it back (runs about 32 degrees at light load low rpm cruise, drops to 27 degrees by 128 LV8) and it is pretty darn good. No flat spots during light acceleration like before. I guess the wideband is worthless for me at part throttle. I hope it is good at WOT because it's about all I have to go by.

WOT tune was WAY rich now. Changed tons of stuff to get it where I like it. Picked up some audible knock so I knocked the overall WOT timing down from 36 to 34 degrees to get rid of it. Car pulls HARD. From a 20 mph roll it will just ignite the drag radials even when they are hot, and that is without spraying.

Threw the previous closed loop tune in just to see what would happen after all the changes and with the hotter plugs. WOT AFR was WAY lean. Like low 14's. I'm thinking I was losing that much power with the plug wires, cap and rotor, and cold plugs. Why else would I need to add that much more fuel after the changes? Sure feels stronger, and most importantly, the cut-out is not bad at all now. What is left feels like a surge instead of a cut-out or miss so I'm assuming that the only way to completely clear it up is a set of 3.73 gears in the rear.

Thanks again for all your help and suggestions! Now I gotta get to work on my nitrous setup. Couldn't figure out why it wouldn't lean out some no matter how big of a nitrous jet I put in. Turns out my nitrous feed lines are smaller than my nitrous jet. :-(

I had a similar problem on my setup and it dissapeared when I enabled AE at 5% TPS instead of the 1.2% it was set at in the bin.