TankT

have a twin turbo tpi setup. it just started missing under boost. it use to run fine. when i get it to 0 ( no vac or boost) you can hear it start to miss. if it gets 2-3psi it will miss really bad and start stumbling. if I mash the gas I get 8 psi and it sounds like it wants to go but you can feel it missing. if I keep it out of boost it runs fine. have a brand new accel coil, wires, cap and rotor. check the plugs and they all look good. very clean. I'm going to change those next and make the gap smaller and see if it helps. any input??

5678TA

you have the ignition stuff checked, what about fuel? sounds lean.. hows the fuel pump?? fuel pressure?? IMO, in a boosted car, you should have all the vital gauges in the car.. boost, A/F, fuel pressure, oil pressure, water temp, and of course: fuel level..

you should at least get an A/F ratio meter.. best investments i ever made.. i bet you're reading above 16.0:1 while in boost.. i wouldnt keep making it stumble till you get this fixed.. lean + boost= detonation happy..

TankT

I do have all the guages. fuel pressure is at 55psi. I have a F.A.S.T WB. A/F is 10.0 at 2-3 psi. I know thats really rich but I have tried everything to lean it up and it wont. I think its seeing a RICH condition because its missing. I think. when at full throttle, 8psi, A/F is high 12 but still feels like its not accelerating. like its missing. or no power. it only use to do this stuff every now and again. and in trying to find the problem, it has gotin worse. it does it all the time.

5678TA

part throttle is supposed to be a little rich but thats pretty rich.. not sure how TPI stuff tunes out but is the timing where it should be?? if the A/F ratio is fine, only other thing to look at is if all cylinders are firing and initial and total timing..

have you thought of a boost referencing regulator?? it will ramp up fuel pressure in relation to boost. could help you lean out the lower boost numbers if you dont have one.. still doesnt help the miss though.. just swap the ignition parts and see what happens..

TankT

just replaced spark plugs. gap .35. still no fix. fuel pressure does ramp up. idle its 40psi and under boost its 50psi. everything ignition is brand new. replaced it all trying to fix problem. checked base timing and its at 6. going to go check total timing if I can find a program that shows it. im using winaldl and it doesnt show it.

jonarotz

iTrader: (26)

What are you using to control everything? Is it a factory ECM? Is this a new problem, was it running right before?

TankT

Well, i believe I fixed the prob. It was a loose ground to the neg on the coil! I swear I checked everthing a thousand times. I dont know how I didnt see it right away. it was in plain sight. Thanks for everyones help.