my 01 is also odd when it comes to idle, I do have a manual so mine also acts up. Some things to try:
1) Usually your idle bypass valve wont cause this, it will just NOT let the car idle and it will die when in neutral or what not... but its a cheap part and easy to swap. If you look at your upper intake you will see this item on the passenger side next to the firewall, bolted to the intake, its cylinder shaped and the cylinder is nearly mounted side ways.
2) Clean your MAF wires especially if you have an aftermarket air filter... and especially a week after you have re-oiled your aftermarket air filter, then again after a month. Use on contact NO RESIDUE electronic cleaner, get it at autozone or radioshack.
3) Try resetting the computer by taking the negative battery terminal off and then tapping the brake a few times let it sit 30 min to be sure (doesnt need to if you are in a hurry a couple does fine) then crank it let it idle for 3-5 min then drive it normal and hard then normal and let it sit for 3-5 min at idle and turn it off. See if this helps.
4) The idle decay rate is controled by the computer its what causes the rpms to slowly drop vs drop like a rock, mine every now and then will get stuck.... aka the rpms will stay way high at a given rpm and wont come down, in this case the mine fixed its self, but yours may not. To fix you can get a chip set to recalibrate the idle decay rate and what not but its probably the most expensive out of any of these to fix.
start with the maf wire cleaner then the idle bypass valve first.
2003 Cobra Vert (Redfire) #3938 of 5082 @ 05/27/2003
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