Random missfire prolbem help!!

[pimpin81]

So I have a 91 eagle talon tsi auto awd, and the past couple of months its been going down hill, I had a friend scan it with his snap-on diagnostic scanner and it pulled a couple codes random misfire and 02 witch was acting lazy.


So i replace the 02 with a known good one and symptoms improved for a while, but Under light throttle at cruising speed it will stutter like uhhh then fine then uhhh and so on its sporadic and not consistent, but then every once and a while ill come to a stop sign and it will start running on 3 cylinders until i rev it up then its fine again. and before replacing the 02 it would actually die once and a while while coming to a stop. runs better then it did with a lazy 02!!

Doesn't act up at all under full throttle just at cruising speed under light throttle it will stutter from time to time and every once and a great while CEL will come on and it will be running on seems like 3 cylinders.


I performed all diagnostics the scanner suggested, replace 02 took power tr unit plug off to check for corrosion, ect.

I'm thinking it the power tr unit but i know basically nothing on their function.


Please help !!! I dont know whats going on with it . ive checked all connectors and vacume hoses and found nothing to suggest a prolbem.

 

[2GFWDbeast]

try doing some simple things like replacing the spark plugs, spark plug wires, and coil pack.

 

[razrman8]

Like suggested above, if you ever have a misfire/ignition problem, one of the very fist things that you can do is replace spark plugs and plug wires. They certainly can not hurt anything and can change quite a bit. Often things are overlooked and over-thought.

 

[pimpin81]

Well Ive already replaced the wires, and the 02 sensor, and check all the plugs which appear to be firing just fine. there not black or oily or gas soaked.

 

[2GFWDbeast]

you know someone with another ecu that you can swap out

 

[razrman8]

well ive already replaced the wires, and the 02 sensor, and check all the plugs which appear to be fireing just fine. there not black or oily or gass soaked.

Replace your plugs to be sure of it.

 

[95gst16g]

Have you actually ran a boost leak test?clogged injectors?Fuel filter?

 

[pimpin81]

haven't ran a boost leak test, as i have no equipment to do it. i have a 5speed
1g eprom ecu but it wont run right without a 5speed afpr, and 450s . i also replaced the OEM HAHA fuel filter 4 months ago after i got this thing to dd status. Maybe its clogged up a bit again who knows.

i have the only auto awd in my area. I'm not a newb by any-means Ive had multiple dsm and done engine and tranny swaps, but this gremlin has got me by the kahunas.

its eathierspark issue the power tr unit or an injector problem im almost positive

its fuel or spark or ecu plain and simple. its not a vacuum leak or a boost leak. it only does it a cruising speed with very little throttle. at full or half throttle it accelerates normally with no hick ups. i don't think its the ecu either because its so random a bad ecu will have a more consistent problem not so random. so that leave fuel or spark, why i suggested the power tr unit, or yeah around the same time this started happening the idol started oscillating randomly but maybe like 1 out of every 20 starts and will stop oscillating after about 1 minute when car starts warming up.

oh yeah when i bought this car 6 months ago i had to replace the tranny and the cv axles and the tcu , so all regular maintenance was performed at that time. I'm wondering it the fuel filter is clogged again, i drained some gas out of the tank a while back into a clean can because the fuel filter had milky gass in it yeah i know, but nothing in the tank looked bad so i just replaced it and it ran great for 4 months now this damn gremlin !!

It cant be the fuel injectors unless its failing randomly and only happens at cruising speed because i don't hit fuel cut ever.

 

[pimpin81]

so does anyone have any real advice instead of check your spark plugs

 

[pimpin81]

I think i found the Gremlin, so far the car is running alot better but its only been 50 miles so far. I found a small amount of water hanging out on top of my fuel pump probably shorting it out from time to time.