I filled up on off brand gas when i was empty. I made my way home on a 2 hour trip and floored it to 120mph when I heard a clunk and then my check engine light flashed. The car began to idle very low but didn't stall. Then about 20 minutes later the light went away and the car seemed ok. About 10 minutes later it came back so i brought it to autozone for a check. There was a miss fire in cylinder 4 so i bought a set of new spark plugs and got them installed. The installer said that 2 of the plugs were fouled and cylinder 4's plug was loose. So i picked the car up and on the car ride home it started idling weird and being slow and rough. I drove the 2 hours home and when i got home it stopped acting weird. So i figured maybe the gas was bad. I went about a week with no problems.
Last night i was racing a car and i downshifted into first with the tap shift. When i did this i heard a big thud. The check engine light came back on and my car was doing the same thing it was a week ago but after like 15 minutes it was fine again.

WHAT IS GOING ON WITH MY CAR?!?!?!?

 

Torque converter going out maybe? Just a guess.

 

Despite what you may think, these cars are not made for a continuous beating. . .like it sounds you are doing. I think converter sounds like a reasonable guess.

 

that will cause the engine to run rough? like really harsh vibration at idle, sound weird, idle lower?
And what about the spark plugs going bad?
Also that would trip the check engine light?

 

When you find out what the trouble is let us know.

 

Does the problem persist when you idle in park or neutral?

I don't know what to make of the thud. If it were engine internals I don't think it would right itself - but that is just a guess.

On other GM FWD cars I have seen where the lockup converter would not unlock and the car would shutter and stall out. On those late 80's/early 90's cars you could disconnect the lockup converter connector and it would behave fine (just not locking up) until you replace the solenoid that controls it.

Maybe the thud is some effect when the lockup finally lets go under power. I assume you do not feel any drop off in power when this happens.

 

Well, I know all too well about misfires and those wonderful P series OBD-II codes...LOL..if you f'd a plug, you will get a DTC or CHECK light..our cars, its the lil engine guy...I had the same experience as I was tuning my N2O and completely burned the plug from the ground strap and base ring...I got a Multiple Misfire Code with that one...the car ran really rough at idle, then once in the throttle, it would even out a lil bit...but the kicker is, that the engine light went on a day or so after the initial run that did it...it took a few drive cycles(so we determined) there was a guy with our motor in the MCSS did the same thing on his wet shot...we were both running the LS recommened NGK TR-6's gapped at .35 for N2O....well, he had the same problem as I did, but unfortunetly he wasnt as lucky...his plug did the same thing, with the same syptoms as mine, and even the same time frame: a run after the first intitial tune run...then a day or two later the engine light screams and the car starts to run and idle a lil rough...then will seem to be fine...he wansnt lucky in the token I was, as his exhaust valve took a hole from the burnt spark plug!!!...that was too close for me....which is why I fixed my problem and knock on wood havent had anyother issues and switched to NGK BR7EF's...these have held strong and are 2 heat ranges colder and seem to be the fix to my N2O woes....but, with sacrafice...they are VERY prone to Fowling out...just the nature of the beast...BR7's also worked out really great for me because now im going to be boosting as well...and I get to hang with the same gap...I would recommend these plugs for any power adder application with this car...but just a recommendation, Im not licensed or qualified to give any information, this is all trial and error and our own research with this motor...
But, I got the Multiple Cylinder Misfire Code when the plug was completly burnt and chunked with the TR-6's...but my last experience was with just a simple misfire, it was Pseries 07...that was just #7 misfired...not like the other...I didnt have any real noticable performance issues...it did idle a lil rough though....but not like you were discribing...but, sure enough, when checked...the plug was f'd. I guess my next question would be, have you changed any timing in it or had it tuned or added anything besides the "Possible Bad Gasoline"??

 

i have not changed anything recently, it is running great now and i beat on it a few times since so i dont get it. I guess my torque converter could be going bad but i dont think that trips the check engine light

 

I had similar problems, turned out to be a loose plug wire. The stock wire wasn’t clipping on to the plug. You should check the wires and make sure none of them are loose.

 

i was thinking of replacing the wires and coils

 

SM,

See if the code got stored in the memory of the PCM. It should be and then get the numbers and go from there. Let us know.

-Mike

 

yeah...find your DTC's when you get flashed...thats a start...and yeah..try taking out the plugs...if your gettting an engine light, there is a DTC or OBD-II code that will go right along with it...if its misfires and exact cylinder...change the plug in that cylinder...you can only trouble shoot at this point...as you already are doing...it sucks...

 

can a scanner from autozone pull a code that doesnt show up anymore?

 

It should be able to pull them still even if the code went away. It would be in the history.

I would sheck out the Aeroforce Scan guage. It about 225.00 or so and will clear and read codes. It does a ton of stuff. Plus it fits right in one of the air-cond. vents. It also plugs directly into the OBD port under the dash.



-Mike

 

yeah....those gauges work wonders...i love them..they helped out quite a bit when i was trying to work through my problems with my plugs...

 

the problem still hasnt come back? wierd i might take it racing tonight so we will see how it holds up.

 

everything was running fine until i got into it again two days ago. I reved it past 6500. They i kinda lost power and now its making a clicking noise. It also isnt running well. I am thinking it was a spring going bad the whole time and that finally did it in.

 

WTF are you revving it past 6500 RPM's for, no wonder why you are haveing problems with it!

 

Holy crap Batman!!! I always keep stock wide open throttle shift points. I bet you collapsed a lifter. Just guessing though. Let us know what you find.

-Mike

 

my tuner set the rev limiter that high. I never go above 6500 though. Usually i shift just past 6200. And i am hoping it a dead spring. It goes to the shop tomorrow.