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1995 lumina poor running condition
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ramguy03
New User
Dec 28, 2007, 8:23 AM
Post #1 of 6
(1952 views)
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1995 lumina poor running condition
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I am having trouble diagnosing a running problem on a 1995 chevy lumina ls, with a 3.4l dohc engine. i was hoping someone on here could assist me with this. on cold start, the engine misses and you can smell the raw gas in the exhaust, as it warms up, it gets better. it is driveable once it gets warm, but it still has a slight misfire. if you pull each spark plug wire off to try to determine where the miss is, the rear 3 cylinders do not make a difference. these should be cylinders 1, 3, 5 if i'm not mistaken. if you pull those spark plugs out after running the car, they are soaked with gas, the front 3 look normal. i have tried numerous things to try to fix this problem, the ignition module has been replaced, i pulled the plenum off and replaced a section of rubber vacuum hose to the fuel pressure regulator that was deteriorated. compression checks out fine, about 180 psi on all the cylinders. i borrowed an ecm from a junkyard also, but nothing has helped solve this problem.
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DanD
Veteran
/ Moderator
Dec 28, 2007, 10:56 AM
Post #2 of 6
(1946 views)
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Re: 1995 lumina poor running condition
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I would try having the injectors professionally cleaned. They might be tarnished to the point of sticking open while they’re cold?
Don’t waste your money on the pour in the tank cleaners; they are more of a maintenance product, in an attempt to keep things clean. If your injectors are the cause of this, they’ll need a concentrated dose of cleaner, if there is any hope of cleaning them at all.
One thing wrong with my theory; why is it just the rear bank of cylinders; it’s not uncommon too see two or three injectors become dirty and not all injectors but all three in this case, on one bank; could be I guess?
It also could be an intake gasket partly sucked out of the thing, that when the engine is cold, false air is being drawn in, causing a lean misfire. Once the engine warms up, the gasket may seal, due to expansion?
Dan.
Canadian "EH"
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ramguy03
New User
Dec 28, 2007, 11:28 AM
Post #3 of 6
(1943 views)
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Re: 1995 lumina poor running condition
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it is possible i guess about the injectors sticking when cold, but i did have my pressure gauge on it and it sat overnight and only lost maybe 4lbs. of pressure during that time. i didi spray 2+2 carb cleaner around the intake the best i could, and it didn't make a difference on how the car ran, so i believe that eliminates the intake gasket. it almost seems like it doesn't have strong enough spark to ignite the fuel, but the thing that puzzles me is that its on all 3 rear cylinders, i could see if it was just one or maybe two. i'm going to try to clean the injectors and see what happens.
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DanD
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/ Moderator
Dec 28, 2007, 11:55 AM
Post #4 of 6
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Re: 1995 lumina poor running condition
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I don’t mean the injectors are sticking while sitting static but maybe better said not closing fast enough when cold.
Spraying the intake with carb cleaner is fine for checking an external leak where you can get at.
But it doesn’t help if the gasket is leaking from the underside; which may mean pulling the intake to examine the gasket and then replace it.
Aren’t cars fun?
Dan.
Canadian "EH"
(This post was edited by DanD on Dec 28, 2007, 11:57 AM)
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Double J
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Dec 28, 2007, 2:24 PM
Post #5 of 6
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Re: 1995 lumina poor running condition
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i'm with dan on this....from what i can remember ( as i said in the past,out of all the things i lost its my mind i miss the most)...from my time at chevy...the 3.4's were known for intake problems...we replaced many....
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ramguy03
New User
Dec 28, 2007, 6:39 PM
Post #6 of 6
(1923 views)
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Re: 1995 lumina poor running condition
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thanks guys, i'll pull it apart and see what i find. i've done the intake gasket twice on this car in the 150, 000 miles it's been on the road, although both times it has been an external leak, once coolant. it's worth a shot, because i've been pulling my hair out on this thing for a while now. thanks again.
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