1991 Pontiac 6000 v6 3.1l running rough
Sounds similar to mine, I've got a 91 3.1 3sp as well. My car itself has a dead cylinder in it that's never affected drivibility, I know weird eh, #3 cylinder is stupid low on comp. My car started an idle hunt today which prompted me to do a few quick online checks and therefore I am here.
Few things I would check, CTS or coolant temp sensor, O2 sensor may be going bad, both of these will sometimes trip a code, but not all the time. And both of these are diretly related to the temp of the engine, when they are clod they do a completely different job then when the engine is at operating temps. These are also the things I need to check regarding my issue of idle hunt turned into SES light and good idle. It could be a vacuum leak, however be reminded it could also be a vacuum leak, I would check all the hoses and also do a spray test around the intake where it mates to the heads, use starting fluid, and spray the mating surface as close as you can get it WITH the engine running. If there is a vacuum leak there the engine will pull in the starting fluid and will generally stall.
Depending on loudness and the type of knock / rattle it could be a dead lifter. They can get extremly loud, and by running that much seafoam through the crankcase could have inadvertanly turned things worse by breaking something up that didn't need to be broken up, as stupid as this may sound it could be the case, I've seen more engines break from running a degunkifiying substance through it then they've helped usually becuase they remove all the crap that the engine is USE to having, will leave you with looser tolerances in bearings which creates a drop in oil pressure which can result in a spun rod bearing, and could be the cause of this knock... If the car itself SOUNDS like it is running ohkay.. it's probably just a dead lifter. Valve springs don't usually break. If the car started to run rougher, like it's missign another cylinder then I would check for a spring broke but not before then.
My .02 now I have to figger out what broke on mine so I can fix this stupid idle hunt.
Update on mine, Code 44
?Prolly the EGR valve that looks like it's leaking something feirce and blwoing soot all over my throttle body :o..
91 6000-LE 3.1 3sp 160k
92 Astro 4.3 CFI 4sp 400k
97 Grand Prix GT 3.8 4sp 156k
03 Sebring LX 2.4 4sp 98k ( the one that doesn't run, needs head, damn timing belt )
Last edited by pur3vil; 10-09-2010 at 07:18 AM.