A lemon form the 90’s

[JP]

I have a 91 olds cutlass supreme with the 3.1L with 87000 miles. i have had some real interesting problems with this car. when i bought it it ran great and after time it developed a slight hesitation right as it comes off idle. after that things started to go down hill. it then had a random stalling problem and sometimes it would start right away then it wouldn’t and you’d have to wait for about 20 min. then one day it stalled and wouldn’t start at all. had the local mechanic shop look at it and they replaced the spark control module. ran perfect for about 2 weeks then it was back to random stalling. i took it back and they said it ran lean at idle and had a week injector pulse but they said they couldn’t figure it out or make it stall (was almost out of gas from them test driving it). so i suffered through for awhile and i noticed another cool thing it would do. if u were at a left turn on a red light (car in D foot on brake with turn signal on) it would start surging then stall. If u dint signal it would be fine. then on day it started not wanting to rev up like it was starving for fuel or like it was only ruining on 3 cylinders instead of 6. so i parked it for 2 months and started up and it ran ok but now it runs on really high idle(14F outside) and the temp light came on until it warmed up but after it was good and warm the temp light came back on. fuel pressure has always been good i replaced the iac and the tps + plugs and wires. any thoughts to the problem would be appreciated

Topic

[college man]

Sounds like you may have a vacuum leak with the high idle.
see if this link helps further.

http://www.ericthecarguy.com/faq/solving-automotive-idle-problems

http://www.ericthecarguy.com/faq/solving-automotive-performance-issues

[Ingvar]

I’d just run a can of Seafom through tankful, each, 2 tankfuls in a row. Will clean entire fuel system and some. That what it may simply need. 91 is 91, got all kinds of crud there.

[JP]

once it warms up after 15 min or so it will finally idle lower. i have looked for vacuum leaks but as it is a poor design lots of vac lines go under the plenum and the only way to get at them is to remove it. i tried sea-foam and when it was in the shop they replaced fuel filter and cleaned the injectors

[Glenn]

Just for kicks, clean the throttle plate really well with carb cleaner if you haven’t done so already…

[James O’Hara]

I also agree with college man it def sounds like a vacuum leak. Use the red straw and shoot it under the plenum. Read through those links he gave you and watch the videos. You will get what I mean by the red straw. Also keep your a/c off when doing this or it might give you a false indication. If it doesn’t work or you can’t get it to do it then follow ukrkoz advice.

I would run the cleaner through the injectors again and make sure you are getting your gas from a good location like shell or sunoco. Then run it through that entire tank. With it being that old and you not being the original owner you have no idea where they were getting there fuel plus it build up over time. If you kept running the cleaner over and over again though it would eventually cause issues but, twice should not hurt anything.

[asetoftools]

Well I had a cousin of that motor. Vacuum leaks were all over the place, on the 2.8 LB6 the intake plenum was not hard to get off, two gaskets and like 10 bolts. Need to also remove the throttle body, but dont need to disconnect the coolant lines, so its a cleanish job. I assume its similar.

But i think it could be an EGR valve with the hesitation at near idle. That’s almost exactly how i described my problem. I would see if you can get a carnival /party smoke machine from craigslist, take off the break booster tube to the intake plenum and pump some smoke in there. See where it comes out. (if no smoke gets out anywhere, prob not a vaccuum leak.) Worked for me and I found a few vacuum leaks one time. EGR’s on these GM motors seem to go bad a lot and can be cheap from the wrecker.

So there is two things you could check. Those smoke machines, from what i can tell, use the same smoke formula as the automotive ones and never hurt my car at all.

Seafoam as some recommend, will kill a bunch of your gaskets on a 91, that’s for sure. Well it will show them to be weak. I think your best bet is a smoke machine for vaccuum leaks. Some say a cigar will work well, but a smoke machine / fog machine will pump much more through the system than your lungs can.

[Author]

Replies