Rough idle
Rough idle My car has a very hard time idling and I'm not sure why. Its a 2001 ls1 with a 98 cam in it with LT and an slp loudmouth. When I used a Snap On scanner and looked at my data I noticed that my ignition timing at idle was jumping around anywhere from 14* to 21*. Is this normal? This is a fresh motor with less than 300 miles if that helps. Thanks
That's the adaptive spark, busy trying to maintain
a fixed idle RPM. It's normal. Kind of low advance
though.
I would suspect that maybe idle mixture is bent
by mistrimming, making things "soggy" and giving
the idle control loop a hard time (if the motor is
too slow to respond, it gets unstable).
If you are in open loop, does it idle better, and
get into trouble once warmed up? Think about
what makes the idle, worst.
a fixed idle RPM. It's normal. Kind of low advance
though.
I would suspect that maybe idle mixture is bent
by mistrimming, making things "soggy" and giving
the idle control loop a hard time (if the motor is
too slow to respond, it gets unstable).
If you are in open loop, does it idle better, and
get into trouble once warmed up? Think about
what makes the idle, worst.
TECH Fanatic
Joined: Feb 2004
Posts: 1,259
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From: Lexington, KY
If I understand correctly, you are running a factory 98 cam. Not sure what mods you have but the spark jumping around is normal, like Jimmy said. You can tweak this with tuning software, but if your running a factory cam you shouldn't have to. And this probably wouldn't help your idle problem. It should idle ok with the factory tune. I would look for a mechanical issue, though as far as power is concerned you would benefit from a tune with the headers.
ok thanks guys. I am going to check my cam timing one more time just to double check. When setting cam timing is there a specific side of the timing chain that needs the tension on it?
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I have looked insanely hard for a vacuum leak, and I wouldn't be pulling 16hg of vacuum with a leak would I? And my LTFTs are reading at a -1.8 or so. I have a very small amount of slack in the chain but only on one side(only about 1/16th of an inch or less). I have entertained the idea of a leaky seal on the bottom of the intake??
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