95TAGary

iTrader: (4)

Ok, This whole summer my 1995 TA (LT1) has been misfiring and I get hesitation after I go for the first mile or so then smoothes out and runs fine like nothing has happened. My car will run fine until I go in a store or something and it does it again when I take off. Almost like something has to heat up to run ok but cools and starts over after I hope for 15-30 minutes. The car backfires a few times out the exhaust until it smotthes out. I've cleaned the throttle body and MAF screen etc. but nothing has helped, starts fine. Any suggestions? Thanks

kingtal0n

iTrader: (1)

sounds like an injector is leaking, draining the rail into a cylinder when you shut it off. You restart it and the cylinder misfires until all that fuel is gone then it straightens out.

Confirm by watching fuel pressure when you shut off the vehicle, it should stay put for a while and not drain down fast. (most cars)

95TAGary

iTrader: (4)

awesome info. Do you think it could be a oxygen sensor?

kingtal0n

iTrader: (1)

you can unplug the O2 sensor(s) to confirm that it has nothing to do with them.

A long term fuel trim could be saved in a computer memory (you might want to reset the ECU just to be sure its isn't LTFT aka "memory" fueling) but the symptom sounds nothing like O2 sensor related. Unless the ECU Can switch off an O2 sensor(s) by recognizing they never flip (go "high" from "low") which is possible. I don't know if the OEM ecu in your car can do that, though.

SS RRR

iTrader: (2)

If this is happening at cold startup then no. O2 sensors do not play a roll in fuel mixture until the engine is at operating temp and PCM goes into closed loop.

ACE1252

Anytime you are getting back firing, I think timing should be looked at. That being said, the opti is always a suspect in these situations.

Check the simple things first....bad plug(s), bad plug wires, then move on to looking at the ignition module, coil, opti, etc.

As king mentioned, might be some kind of fueling issue, but you are going to have to do some trouble shooting to see if that is the issue(injector checks, fuel pressure checks, etc).

I will mention one other thing....I had a 3.1 V6 Z24 back in the 90's that starting having some rough idling issues when cold. When it would get hot, thing were just fine. No trouble at all.

Turns out, that it had cracked a cylinder wall and was sucking in coolant when cold(causing the rough idle) then the crack would get smaller when hot causing it to smooth out...the hot engine helped with the combustion as well.

It was also losing coolant out the overflow. I had very little knowledge of how cars worked back then so I didn't realize that pushing coolant out the overflow was a very bad situation.

That particular block had known issues cracking blocks, but to my knowledge the LT1 does not. However, you might be losing a head gasket.

Given you didn't mention any cooling issues, I'm guessing this is not what your issue issue is....but just to ask...

Are you having any coolant loss issues or strange cooling issues by chance?

kingtal0n

iTrader: (1)

the backfires are 'out the exhaust' which presumably is the fuel from the leaking injector passing into the exhaust and exploding there until it is gone

ACE1252

Or an ignition/timing issue where the fuel is not being burned and then pushed into the exhaust.....might be either one....he needs to check both.

kingtal0n

iTrader: (1)

oh yeah, but thats just obvious because opti. its so obvious it doesnt need to be said, obviously when opti is involved its a 50/50

95TAGary

iTrader: (4)

awesome reply though, no I don't see any loss in coolant on floor or any leaks anywhere, I plan to take it to the shop to leave for awhile cause this keeps me from driving the car