# Need help with severe stumble



## draney (Apr 16, 2010)

Recently installed the engine,ECM,auto trans, etc from a 04 GTO in a 65 LeMans (now a clone GTO). Only mods to the engine are a 01 Z06 cam, springs, and 06 Vet MAF. My tuner did his usual tricks--disabled stuff I'm not using and loaded a tune for the cam etc. Everything works great except if I dump the throttle at low speed and RPM it stumbles terribly. I can't break the tires lose and that's no fun. If I back out of the throttle and baby it alittle it catches and takes off like it should. We did a dyno tune on it and got it to 300 RWHp. We believe we have the traction control off and all toque mgmt disabled but apparently the ECM is raining on my parade for some reason.

Any thoughts or suggestions would be appreciated.

DRaney


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## Rukee (Feb 8, 2007)

Is the tranny kicking down when you dump the throttle?


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## GM4life (Mar 18, 2007)

Rukee said:


> Is the tranny kicking down when you dump the throttle?


Good question.

Did you bring it up with the tuner? What tranny are you using?


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## draney (Apr 16, 2010)

It has the stock tranny and I typically dump the throttle with it in low and it will eventually upshift after it stumbles around for a while. If I hold the brakes on it will stay in the stumble mode at around 1500 RPM. If you are cruising along in a higher gear and dump the throttle it stumbles briefly, downshifts and then catchs pretty good. My tuner (I am referring to a technician) uses HP tune and he has downloaded files into the ECM (several times).


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## jpalamar (Jul 22, 2008)

Sounds like the tranny isn't tuned right, assuming it is an A4.

Get your tuner to give you the tune files on a thumb drive or somerthing, them post them on HP Tuners forum. I'm sure someone there would take a look at it for you.


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## GM4life (Mar 18, 2007)

draney said:


> It has the stock tranny and I typically dump the throttle with it in low and it will eventually upshift after it stumbles around for a while. If I hold the brakes on it will stay in the stumble mode at around 1500 RPM. If you are cruising along in a higher gear and dump the throttle it stumbles briefly, downshifts and then catchs pretty good. My tuner (I am referring to a technician) uses HP tune and he has downloaded files into the ECM (several times).


I'm assuming your using the 4L60-E or 4L65 transmission. They have their own controllers called TCM's. Is it bogging like in lugging the engine or slipping? To me if it stubles the engine has a problem in the tune. Your tuner should drive your car with the computer hooked up so he knows what your talking about. Has the transmission fluids and filter been changed?


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## draney (Apr 16, 2010)

It' not the trans---checked that out first. It's a definite engine stumble. Guess I'll keep bugging my tuner. Thanks


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## Jerry64 (Apr 20, 2010)

Check the min./max. voltage to the TPS plus voltage over the range........JB.


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## draney (Apr 16, 2010)

TPS voltage is good. Have also checked all the other normal things--MAP, MAF, Etc. I suspect it is related to torque mgmt or traction control. Tuner believes all that is supressed but--. Note I have no BCM or ABS module. Since the ECM cannot communicate with the other modules could it be going into some default, "blind", traction control or torque mgmt mode???


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## Jerry64 (Apr 20, 2010)

You say trannie is o.k.....But could the convertor be in lock-up and not un-locking.Is the switch wired in?The convertor should stay un-locked out of drive........JB.


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## GM4life (Mar 18, 2007)

Jerry64 said:


> You say trannie is o.k.....But could the convertor be in lock-up and not un-locking.Is the switch wired in?The convertor should stay un-locked out of drive........JB.


I was thinking the same thing. But the car would die if the convertor stayed locked. Its a pain in the ass to drive when the converter is locked all the time. It will bog the car down when slowing down and accelerating. It will act like a stick shift car left in 5th when slowing down and turning a corner.


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## jpalamar (Jul 22, 2008)

draney said:


> TPS voltage is good. Have also checked all the other normal things--MAP, MAF, Etc. I suspect it is related to torque mgmt or traction control. Tuner believes all that is supressed but--. *Note I have no BCM or ABS module.* Since the ECM cannot communicate with the other modules could it be going into some default, "blind", traction control or torque mgmt mode???


Are you sure your not in Safe Mode? When Julie's wheel hub failed she got an ABS error and traction control turned off. Then it went to limp mode. She was on 05 A4.


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## GM4life (Mar 18, 2007)

draney said:


> TPS voltage is good. Have also checked all the other normal things--MAP, MAF, Etc. I suspect it is related to torque mgmt or traction control. Tuner believes all that is supressed but--. Note I have no BCM or ABS module. Since the ECM cannot communicate with the other modules could it be going into some default, "blind", traction control or torque mgmt mode???


If there is a way to have the ECM ignore the stuff that you deleted thats fine. But you may have to look into getting a stand alone aftermarket engine controller ie Bigstuff, ect. Are you using the TCM? If your tuner can check the perameters in the TCM and see what its doing. I thought I heard from someone you cannot compleatly turn off TM or Torque abuse in the tranny.


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## draney (Apr 16, 2010)

Pretty sure the tcc is unlocked. It does it from a dead stop.

Also have new clues--got a friendly GM tech to put a tech 2 scanner on it. The most obvious and only abnormal thing we noticed is as soon as it goes into this "funk" mode the injector pulse widths (PWM) freeze. They do not change until you get out of the throttle.


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## draney (Apr 16, 2010)

I'm sure the TCC is not locked. It does this from a dead stop. 
Do have new clues---got a friendly GM tech to put his tech 2 on it and we noticed that the injector pulse widths freeze when it gets into this "funk" mode. As soon a I slam the throttle the pulse widths stay at the same exact number until I release the throttle---


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## draney (Apr 16, 2010)

Pretty sure trans is ok and TCC is unlocked. I did get additional clues--friendly GM tech put a tech 2 scanner on it and we noticed that as soon as I go to WOT the injector pulse widths "freeze". Pulse width stays on the same number until I get out of the throttle. Engine hangs at 13200 to 1500 RPM. No miss etc. just no power to accelerate.


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## draney (Apr 16, 2010)

draney said:


> Pretty sure trans is ok and TCC is unlocked. I did get additional clues--friendly GM tech put a tech 2 scanner on it and we noticed that as soon as I go to WOT the injector pulse widths "freeze". Pulse width stays on the same number until I get out of the throttle. Engine hangs at 13200 to 1500 RPM. No miss etc. just no power to accelerate.


FOUND IT----the brake pedal input to the PCM was not connected. The PCM thinks the brakes are applied and apparently tries to keep you from killing yourself, wiping out the brakes or trans, etc. Got it connected correctly and life is much better. Thanks for the inputs--


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## GM4life (Mar 18, 2007)

That cool that you fingerd' it out. The simple things can be a pain sometime.


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## Jerry64 (Apr 20, 2010)

Great......now let's see some pic's of that set-up.........JB.


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