boostedlt1

iTrader: (2)

posted this a while back... still having the same problem.. just not as bad.


this all started when i did a head gasket swap. only thing that changed during the swap was the gaskets, bumping compression from ~9.1:1 to ~9.4:1

afterwards the car started randomly dieing whenever i'd slow down or was idling. the fuel pump would turn off, (thus making me lose fuel pressure), and it'd throw codes for:

ignition system grounded
ignition system open circuit
loss of hi-res signal
loss of low-res signal
fuel enable malfunction
pcm error


checked all the grounds, tested fine.
put a new pcm in, nothing changed.
re-did all battery cables in 0 gauge, nothing changed. (car runs @ ~14.2 volts)
changed opti and icm with known good ones, nothing changed.
tranny was messed up so got a whole new build with a stall

after the tranny install it was still doing the same thing, wouldn't even idle in the driveway. i went back to the original pcm and throttle body, and now it's driveable, it'll try to stall but usually doesn't actually stall.

it ONLY stalls/wants to stall when i'm either
1. cruising then completely let off the throttle to 0% TPS
2. stopped and idling

it never does it while cruising or accelerating. i can feel/hear it start to cut out the second i let off the gas, it's like everything just dies, i can stab the gas and nothing will happen for about a second or two, then it'll all come back to life and ROAR!

it seems like it usually does it when it downshifts from 4th to 3rd, if i'm under ~30mph it doesn't usually seem to do it, mostly just when i let off in 4th from 45-50mph


someone pleeeeaaassssseeee help!!!

Ballinonabudget

iTrader: (12)

Hrm... wtf. Shbox will probably chime in, he may have an answer for you. In the mean time, check out his site, it may help.. www.shbox.com .

I've had shut off issues from VATS before, and also from my PCM and opti. But if you're saying you swapped those already and the problem persists idk what to say. Did you check ALL your wiring, especially near the PCM, and everything to/from everything ignition related? Try a new opti harness?

stevo9389

something wrong with your IAC? using the stock TB?

boostedlt1

iTrader: (2)

i bypassed the vats a long time ago

i was running a 58mm throttle body with sensors that came on it, now i'm running the stock throttle body, with the original sensors


i've torn all the wiring apart and cant find anything, took all the connectors off the pcm and tested all the ground, all tested good... but that was just with it sitting.. so who knows...

one weird thing is that it wont run at all with the maf unplugged, i've accidently left the maf unplugged before and it ran fine in speed density, might just be cause it's a different tune? not sure :/ just thought it was weird that it wouldn't even idle with it unplugged

ken125

iTrader: (3)

Its kinda odd that the car will not run with the maf unplugged...... will it fire at all with it unplugged? Mine has some similar symptoms but mine runs the same with the maf unplugged. Are the symptoms the same while it was cold?

Tinbender59

boostedlt1: the fact that it will not run with out the MAF is a big clue.

ignition system grounded
ignition system open circuit
loss of hi-res signal
loss of low-res signal
fuel enable malfunction
pcm error

these are also clues to the malfunction that is afoot. do you have a wiring diagram for your car?? if my gut is right, your 5vdc has been compermised. and or your ground curcuit to the distributor is open.. it is kind of hard to explain, but; it sounds like the power or ground to your OPTI is back-feeding through the MAF. when you remove the MAF you remove the only lifeline that your OPTI has. look at the wiring diagram find all of the components that feed from the 5vdc power coming out of the ECU, usually more than 1 wire. then do a continuity check from the ECU to the component (s) also check the component (s) groung wire to the battery (-) negative, for good continuity. I would bet you will find an open or intermitten ground somewhere. probably one of the wires that attach to the stud on the intake manifold---lightly pull on all of them, look for a "springy" wire = broken copper strands 'Bender' P.S. I have seen crazzier things!!!

LTX

Once the MAF is unplugged it runs in safe mode! not saying its safe though.

Tinbender59

that is corect, "IF" no more than two sensors are down, if there are more than two "bad" or disconnected sensors; the ECU will then shut the system down, to avoid making a bad situation worse. this was incorperated into the OBD2 systems as far as I know

boostedlt1

iTrader: (2)

the car will fire up with the maf unplugged but will immediately shut off as soon as it fires.

i was thinking it might be something along the lines of what you were saying tinbender, i need to find a good wiring diagram and start tracing wires