Think my idle needs to be changed?

[StageLeft]

I want to appologize for making a car thread but it's just no use because we all know it's not the last one you'll ever read, but thanks for reading anyway.

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Last several hundred miles the car idles like a filthy buggar. It has normal power and it has the same great gas mileage as always. It also sounds perfectly fine when it has any throttle (in gear and also out of gear), but when it's in neutral it sounds pretty gross idling. Could the idle speed just fall off like that? I presume I need to get somebody else to fix that...at first it would only do it sometimes but now it does it all the time in neutral. I'm not sure though if it's just a bad idle speed or some deeper engine problem.

For what it's worth 1300 miles ago I added a stop leak to the oil. I doubt I'd do something like that again but it was a lapse in judgement. I kind of felt a little iffy about all that and gave it an oil change yesterday with standard oil so if that could have caused the problem then the stuff should be flushing out soon, unless it caused permanent engine damage (from diluting the oil too much with stop leak), but if it caused permanent damage wouldn't I notice that other times, and not just when it idles? Like I said it's been like this for several hundred miles.

Also it does it when it's hot or cold. Sometimes after starting and it turns over a second or so later the revs drop real low like it wants to stall, but it never does, and it never gets that close again after you've driven it anywhere at all (like at lights).

Any ideas are great

 

[JC]

What kind of car? Engine? Miles on it?

 

[StageLeft]

Originally posted by: JC
What kind of car? Engine? Miles on it?

93 Sentra, 157k, 5-speed. Overall the car is in excellent condition and drives nicely.

 

[yobarman]

my car is really messed up...when i'm at a light or inching foward... my car lunges foward a bit without me touching the gas.. it's pretty weird and i dunno crap about cars, but it seems pretty serious. it's like the engine gets little bits of gas sneaking in or something

90' chevy lumina v6, 128k miles.

 

[JC]

Do those have fuel injection? I'd say with that kind of mileage, there's a passage or something plugged that's causing the rough idle. Are you getting any 'check engine' light?

 

[Quixfire]

I'm thinking worn spark plugs, bad wires, Dist cap & rotor (may not have one), drity throttle body, or most likey vacuum leak after mass air folw sensor.

 

[StageLeft]

Originally posted by: Quixfire
I'm thinking worn spark plugs, bad wires, Dist cap & rotor (may not have one), drity throttle body, or most likey vacuum leak after mass air folw sensor.

Spark plugs were replaced with new wires 1400 miles ago to fix another problem and it purred like a kitten after they were done (a mechanic did it).

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It's fuel injected; not getting check engine light.

 

[JC]

I'd say a fuel injection cleaning is in order. I doubt the stop leak has anything to do with this.

JC

 

[StageLeft]

Originally posted by: JC
I'd say a fuel injection cleaning is in order. I doubt the stop leak has anything to do with this.

JC

I hope not!

I read a post on usenet and somebody else mentioned dirty throttle body as well. I wonder if that's it. The reason I say that is ever since I bought the car 15k miles ago I'd get this issue:

10% throttle = 10% power
20% throttle = 20% power
etc.
60% throttle = 30% power
70% throttle = 70% power
etc.

It's like just at that particular point when I'd push down on the gas the car would never respond as well as it should have. That has never gotten worse and it's only at one tiny point in the range of pedal motion.

 

[JC]

Well, a good fuel injection cleaning includes a throttle-body cleaning, too For instance, on a lot of Fords, there's an idle-bypass valve that gets gummed-up, causing irregular idling problems.

JC