WOT bog from dead stop

1227747 $42 ASDU, AMC 360 V8, 86 Jeep Grand Wagoneer. Timing is based on the 'basic timing' table on Binder Planet. I've zeroed out the PE spark advance. At all but near WOT it drives great.

I'm struggling with a bog / stall / popping out the throttle body when I jam hard on the accelerator from a dead stop.

• I've increased AE vs MAP table by ~ 30% or so, to no avail.
• I've tried increasing and decreasing main SA in the 800-1400, 80-85 Kpa range, no noticeable change
• I've tried bumping the VE table at 800/80KPa (it looked low), no change -- at this altitude KPa never exceeds 85.

Are there any other parameters relevant to AE or WOT or Spark or ... ?

In other words... what next? :)

I can post bins, logs, etc.

Got at least 13 PSI fuel pressure?

Bog can sometimes be to much AE, but the popping back is always not enough AE...

30% AE TPS and MAP is not much... on a Vortec head Chevy engine with cam can use more then double!

AE TPS = very short time to compensate for throttle blade opening.

AE MAP = longer time to finish.

Little trick to finding AE tuning needs without a wide band is to cruise steady state like 10% TPS, accelerate to 20%. Watch log at that time, if STFT/INT goes up it needs more AE, if STFT/INT goes down it's to much AE.

Yup. What he said.

I usually changed AE in 50% increments.

Thanks for the help once again :)

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Originally Posted by EagleMark

Got at least 13 PSI fuel pressure?

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Yes, it reads ~14.5 on two different gauges.

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Bog can sometimes be to much AE, but the popping back is always not enough AE..

30% AE TPS and MAP is not much... on a Vortec head Chevy engine with cam can use more then double!

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I will try increasing both parameters.

It definitely acts like lean-out bog/pop on a carb.

Another interesting fact. Something went wrong with emulation and the ECM must have been in limp home mode. When I stomped on the gas, it shot off the line like never before. As soon as I uploaded the bin to the emulator again, it was back to the bog/pop behavior.

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Little trick to finding AE tuning needs without a wide band is to cruise steady state like 10% TPS, accelerate to 20%. Watch log at that time, if STFT/INT goes up it needs more AE, if STFT/INT goes down it's to much AE.

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Good tip. I'll check that out.

I probably should first see if I can lower the static timing below 10.

I'll also re-check / re-set IAC, min idle, TPS, etc.

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Another interesting fact. Something went wrong with emulation and the ECM must have been in limp home mode. When I stomped on the gas, it shot off the line like never before. As soon as I uploaded the bin to the emulator again, it was back to the bog/pop behavior

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LHM is WAY RICH! No AE problems when your that rich.

If you ever have an emulator fail like that always check codes for Error 51, nothing works right with it set... my AutoProm hardly ever glitches and never causes a Error 51, but I recently had a bad ZIF or ribbon.. or just wore it out finally on a G2 adapter 1227747 I use for tuning/testing etc.... I didin't realize 51 being set, even if problem is fixed makes ECM act like a semi LHM? Drove me nuts... cleared codes, replaced ZIF and ribbon and back to normal.

Aw crap. Ok, I'll check that out too.

I've narrowed down the cause to a problem somewhere above my neck. I botched the vacuum routing, EGR, etc., I may have been experiencing a big vacuum leak on top of EGR enabled with manifold vacuum. :doh:Gawd. This is totally embarrassing. That's what happens when I let a project sit for months. Now I get to start ALL over again with the tuning. Yay. :mad1:

I hate when that happens... :innocent2:

Just think how good it will run tuned right! :thumbsup:

You seem like a good candidate to try out my new $42 XDF, patches make it easy to turn off and back on EGR for data logging and also has all the others as parameters that need to be off for data logging... want to use it? Also has patch for Lean Cruise, ESC done, BPW and Spark advance. One click stuff. Have to keep it to yourself till I'm done, you can be beta tester number 2... I was number 1. I don't think there's anything wrong, just want to clean up some descriptions and comments before I release it. Just an improved version of last... if you want to try and give feedback PM me your email.

I've done this often on my FI project. There needs to be a 'high five' smiley or something.