Tip-in stumble and pop?

[turbobuickman]

When I boot it from anything less than 1/2 throttle (or anytime the turbo isnt already spooled) my engine stumbles and I get an intake backfire (my boost guage(s) show a surge in pressure), and then it pulls like hell and runs smooth. The stumble/pop does not happen when I ease into it and spool the turbo slower. I thought it was my MAF, which was bad, but I have recently put in a known good one and the problem still exists. I do know that my throttle shaft seals leak(whistle) which causes my bL on SM 2.1 to read 143 at idle. Could these be related? What might be causing my problem?

Thanks,
Kyle

 

[trbojo]

what injectors are you running? i sometimes had the same problem until upgrading mine. they were original.

 

[turbobuickman]

Stock injectors, pretty sure they dont leak and I put injector cleaner in my tank a couple weeks ago. Any other ideas?

 

[TurboBuickSix]

Have you verified timing chain,cam and lifters up to snuff? Cam sensor timing should be checked to if your not already sure.

 

[2QUIK6]

Mine has done that a few times before at the track, when reviewing my scan file, its been when my O2 sensor was not cycling correctly, was getting no x-counts...if I make sure the O2 is hot and is going thru the x-cnts quickly, its never done it.

 

[turbobuickman]

This happens when the engine is at operating temp (165ish) and in closed loop, I'll recheck the x-counts but I think they were pretty active. I want to make sure im clear that this is an intake backfire and only happens when i first mash the throttle(not high boost or high rpm related). When I get a chance I will reset my tps/iac. Are the high blm's and vaccum leak a common cause of tip-in stumble?

 

[2QUIK6]

Yes, a vac leak could cause tip-in stumble as the IAC is not controlling how much air is entering the plenum at idle. YOu'll find your BLMs high and the IAC count probably at 0 if there is a vac leak. IAC counts being high, abouve 50 or 60 and no vac leak will also cause tip-in stumble.

 

[turbobuickman]

Yep, Iac's are usually around 00 but never more than 07. I just gotta get a hold of some throttle shaft seals. This is probably causing the stumble but would a vaccum leak cause the backfire too?

 

[2QUIK6]

I guess if its too lean at tip-in it could. When my accellerator pump was shot on my carb motor in the TA it would backfire thru the carb at tip in because it couldn't get any gas, too much air for the mixture. I'm just surmizing it could based on that.