Question : 92 Cavalier Convertable run's only sometimes...

[spe183]

I have a 1992 Chevy Cavalier convertable that I am not familiar with (this particular 3.1 setup). I have a 96 olds ciera with a 3.1 of the next generation and a 3.4 in a venture van, worked on both of those but I will admit due to the OBD2 and better ways of tracking things down (for me at least) . I digress though. Back to this car. When it runs it runs beautifully down the road. After running for about twenty minutes I will notice that at stoplights it idles rougher and rougher. Then it starts to stall. It will, at this point, not go over 1000 RPM's even if the throttle is pushed to the floor. If I would let it set it would get better (cold and go again) however now, even cold, it will not run for more then ten seconds (very shaky, missing) and if I give any throttle AT ALL it dies and/or backfires and dies. I have tried the TPS. I have checked fuel pressure. I know on the newer engines if one pulls the vac. line of the regulator and it's gassy that may be a problem however on this old design I think that's going to be under the plenum. I've checked for cracked/leaky/collapsed vac. lines, they are plastic, no cracks, and the ends are good. I am at a total loss here. I read on another forum that a bad alternator causing drag can do this. I pulled the belt off to see if it would run better w/o the load but it's not an issue. I have NO CODES, no SES light unless I unplug a sensor. I tried popping off the 02 sensor wire to see if that would stabalize it. also the MAP, TPS, IAC, CTS I got changes in running (not better) and a light for each one but none of them made a real differnece... another idea from researching around. As I said, I'm lost here, no idea where to go or what to check. It was so odd that it would run great for an hour, as time got by only for about 20 mins, and now not at all. If anyone has input I'd be thankful!

[pocket-rocket]

I've done a FPR in the older 3.1 engines before. That thing made the whole car smell like raw fuel, but if yours doesn't smell like that we still can't rule it out yet. You are correct, though, the FPR is under the plenum, IIRC.

You said you checked fuel pressure, I assume that was with it acting up? I noticed you didn't mention changing the fuel filter. They are fairly cheap, and if you don't know the last time it was changed, it's most likely due.

How does the exhaust sound? Does it sound like the air coming from the tailpipe is being forced out?

[SappySE107]

Could be a coil pack going bad, or it could be the fuel pump going bad. Either way, its heat related and both of those parts will do it. Could be filter or FPR or spark plug or wire or EGR or vac leak but being that its worse as it heats up and I have had the same situation on my 3.1 grand prix, those 2 items are my guess. Fuel pressure doesn't mean you have flow (had that problem, replaced the pump). Only time I had a bad coil pack do the same was with the accel coils.

[rooster5333]

i had a similar issue with my 97 monte carlo ( R.I.P.) after sitting for a long time, my fuel filter blew thru. would start at first, and run rough. but after a couple days, was dead. had good spark. rail pressure was good. sounds like your issue. fuel filter starting to block, then finally blew thru. i tore it down, and found 4 of the injectors were blocked. i cleaned out all inj, fuel tank, new fuel pump, (300 bucks for that octopus) new filter, blew out all lines, and reassembled. but i somehow missed some trash, and it happened again, a few days later. ended up re-doing all again, and replaced original 4 blocked inj, incase some small junk got in. not a difficult repair. but is dirty and time consuming. hope this helps.
P.S. ON A SIDE NOTE. BE VERY CAREFUL IF U PULL THE TANK. I HAD MY CAR ON STANDS WHILE I DID MINE. CAR ENDED UP FALLING OFF ONE STAND ONTO ME. LUCKILY, I HAD ADDED EXTRA BRICKS UNDER THE TIRES, THAT SAVED MY BUT.
!!!!!! YOU CANT BE TOOOOO CAREFUL!!!!!!!!!! YOU CAN USE TOO MUCH CARE, OVER AND OVER!! BUT YOU CAN ONLY USE TOO LITTLE ONCE!!!!!