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Olds Cutlass Supreme - 1994 - ROUGH Idle
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dao1
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Feb 28, 2008, 7:30 AM
Post #1 of 11
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Olds Cutlass Supreme - 1994 - ROUGH Idle
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Car has only 43K miles; got it from snowbird Grammy in Florida so not driven a lot. Has peppy 3.4L DOHC engine - loves to run but idles like you-know-what. I replaced the Idle Air Control - helped some. Have been running Chevron Techron through the gas tank. What should I do next? Thanks!
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DanD
Veteran
/ Moderator
Feb 28, 2008, 8:04 AM
Post #2 of 11
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Re: Olds Cutlass Supreme - 1994 - ROUGH Idle
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With the age and the low mileage on this car, the injectors may have become covered in tarnish, causing them to flow unequal amounts of fuel at idle.
When there were a lot of these engine running around we were finding a number of injector issues. We were constantly doing injector balance tests; finding that there were every few that had a set of balanced injectors. Even a fresh set out of a box; you only had a 50/50 chance in getting all six to squirt the same amount of fuel. Quality control maybe wasn’t at its best back then? LOL
I would start with having the injectors professionally cleaned; don’t bother pouring anymore crap into the tank. That stuff is more of a maintenance item and if this problem is dirty injectors; you need something very aggressive to be run through the injectors if you have any chance of saving them.
Now understand I’m just guessing here because there were other issues with these engines; like intake manifolds sucking out there gasket causing enough of a vacuum leak that they would run like crap at idle; just the way you explained yours is.
Scanning the computer and checking sensor data and IAC (idle air control) counts is about the easiest way of detecting a internal vacuum leak. If IAC counts are sitting at zero and the idle is above what is considered “normal” you likely have a vacuum leak.
Dan.
Canadian "EH"
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dao1
Novice
Feb 28, 2008, 8:55 AM
Post #3 of 11
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Re: Olds Cutlass Supreme - 1994 - ROUGH Idle
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Dan,
Professionally cleaning the injectors make sense - thanks. I certainly don't want to replace them all!
Concerning the intake manifiold eating gaskets, I thought that was only an issue if it ran the orange Dex-Cool coolant - which it doesn't. It's the regular green. Am I missing your point?
I thought of a vacuum leak too, but I'm trying to avoid spending the money to have a shop track that down if I can. Any chance the EGR valve or plugs & wires could be a culprit?
--David O
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DanD
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/ Moderator
Feb 28, 2008, 9:22 AM
Post #4 of 11
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Re: Olds Cutlass Supreme - 1994 - ROUGH Idle
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I’m not talking about the coolant leakage problem with the over head valve engines, but a vacuum leak with the over head cam engine.
Avoiding a garage at times could cost you more money by throwing parts at the thing randomly.
And yes the EGR valve, ignition wires, spark plugs, excessive fuel pressure, low or uneven cylinder compression; all could be part of the problem, but how many could be scenarios should we discuss.
I don’t mean to sound abrupt but there so many things that could cause a rough idle and we've only scratched the surface of what it might be. Take it in and have someone diagnose it; then see if it’s something you can handle repairing on your own?
Dan.
Canadian "EH"
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dao1
Novice
Feb 28, 2008, 10:40 AM
Post #5 of 11
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Re: Olds Cutlass Supreme - 1994 - ROUGH Idle
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No offense taken - I'm fine. I'll get back to the forum when I have some more news to report.
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autojoe
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Feb 28, 2008, 11:52 AM
Post #6 of 11
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Re: Olds Cutlass Supreme - 1994 - ROUGH Idle
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if you take to a garage......they should do a series of checks to find problem of rough idle.Hook to ignition analyzer....do injector balance test to see if all injectors are dropping roughly same amount.....that would tell you if any injectors were restricted.scan tool or gas analyzer might be used.No garage should just clean your injectors for the purpose of curing a rough idle without first determining that the expensive cleaning will not cure your problem.If you increase throttle at idle....does the roughness go away?If roughness only at idle and not under load then may be a leaking injector.When was the last time vehicle had a tune-up?How high is the idle rpm if you have a tach?engine warm?Possible vacuum leak?
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dao1
Novice
Feb 29, 2008, 1:31 PM
Post #7 of 11
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Re: Olds Cutlass Supreme - 1994 - ROUGH Idle
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Here is the current status:
When cold, it starts right up, revs high to about 2000+ rpms (it has a tach) and then drops down to a rough idle at 1000-1200. It sometimes stalls (if it does - it starts right back up). When cold, it has no power and "pops" when I push the gas.
Once warm, it idles at 1000-1200 usually (occasionally goes down to 900 or so - then is rough), but runs fine when given gas. It also smells of exhaust if I'm sitting in traffic.
No tune-up recently (I'm planning to do plugs and wires as maintenance anyway). Just replaced IAC which helped some. I was thinking of EGR valve and fuel injection service, but those cost more. I could believe a vacuum leak too - that's diagnostic money. I like the car and want to keep it and drive it. It was Florida snowbird car so sat 6 months out of the year - 14 years old with 42K miles when I got it.
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autojoe
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Feb 29, 2008, 4:42 PM
Post #8 of 11
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Re: Olds Cutlass Supreme - 1994 - ROUGH Idle
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if you smell exhaust fumes may be an exhaust leak.....check exhaust manifold for a crack.Check for any vacuum leaks.Sounds like a vacuum leak causing too lean mix and when it goes into closed loop 02 compensates somewhat.I use propane to check for vacuum leaks.Thexton makes a adapter for a small propane tank.Before I had that I screwed a adaper on for sweating copper pipe and unscrewed the end piece and put a length of vacuum hose from local auto parts store over that and turned propane on and started car and ran hose along any gaskets and if idle smoothed out I found the leak.Also check for any cracks in any vacuum lines.Check for any cracks in exhaust manifold.Lot of people will tell you to use carb spray and you can but it is flammable and if you spray too heavy and around hot engine it could ignite....just would have to be careful and have a fire extinguisher handy.....had that happen to me once.If you ran hose into intake and turned on propane to ingest some into engine at idle and rough idle went away....that would tell you that it was running lean.without specialized testing equipment you just have to eliminate things.Has the check engine light ever came on?Any stored codes?
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dao1
Novice
Feb 29, 2008, 6:53 PM
Post #9 of 11
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Re: Olds Cutlass Supreme - 1994 - ROUGH Idle
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Hmmm...I'm not sure I'm up for propane in the engine, but I have a friend who might be.
The check engine light has come on a couple of times when I was idling rough stuck in traffic, and then it went off when I accelerated again. I don't know if there are any stored codes - are they stored once the light has come on until it's reset?
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autojoe
User
Mar 1, 2008, 7:34 AM
Post #10 of 11
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Re: Olds Cutlass Supreme - 1994 - ROUGH Idle
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Codes are stored for so many ignition start ups even if light goes out.In park if you give it more gas does roughness go away?I would check vacuum lines and exhaust system.Garages use propane to limp in a no start vehicle into bay.Propane is safer than carb cleaner and starter spray.
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dao1
Novice
Mar 21, 2008, 10:56 AM
Post #11 of 11
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Re: Olds Cutlass Supreme - 1994 - ROUGH Idle
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OK, I've done some more work and now I'm back with an update.
A week ago a friend and I did the Seafoam induction cleaning through the brake booster vacuum hose (that stuff is awesome!), replaced the EGR valve, plugs and wires. We replaced the IAC a couple weeks before that. We didn't check codes yet.
Now it starts right up and zooms up to 2000 rpm and then settles back down fine. The problem is that once it is warmed up, it does not like to idle below 1200 in gear or 1500-1700 in neutral/park. Occasionally, it will drop down to ~800 in gear/~1000 in neutral/park but only after I've been sitting at a stop light for a while. When I'm running at speed, if I pop the transmission into neutral, the rpms surge to 2000 and stay there until I put it back into gear. Pickup has improved and it's running pretty smoothly.
Next steps?
THANKS to everyone for all your help so far!
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