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Re: 1986 16 valve, non turbo idle problem Posted by Justin VanAbrahams [Email] ![]() ![]() In Reply to: 1986 16 valve, non turbo idle problem, Art, Mon, 19 Mar 2001 23:27:23 Members do not see ads below this line. - Help Keep This Site Online - Signup |
If you've checked vacuum lines, and they're okay, and the engine otherwise runs alright, there are two main culprits: The idle control valve (AIC - adaptive idle control) or the throttle position sensor (TPS). Both of these could cause the symptoms you describe. The AIC is tough to check, and they generally don't just fail - usually there will be issues long before they die completely. The TPS is another story - it's a simple electrical switch and when it dies, you'll have trouble idling. Locate the black box on the side of the throttlebody, remove the 3-pin connector off the top. You should get continuity between the rearmost and middle pins when the throttle is at rest, and continuity between the middle and forwardmost pin when the throttle is 70% open.
If the car is not running right, suspect the air mass meter (AMM) or even the O2 sensor or ECU. If one of these is way outside spec, you'll have a funky mixture and be prone to stalling. The AMM and O2 sensor can be tested with a sensitive DMM - I've got no ideas on how to test the ECU, but they rarely fail, so I'd consider it highly unlikely.
All that said, don't overlook the ignition system. Ignition wires or spark plugs in poor shape can cause idle problems, especially bad ignition wires. At low engine speeds there is maximum resistance and bad wires will be more evident. As RPMs increase, resistance goes down and bad wires will be less of a problem. Given the symtoms, I'd say this is not your problem.
I would suggest picking up a $40 Bentley manual from one of TSN's sponsors - it's pretty much invaluable at troubleshooting these types of things. And fun reading. :)
-Justin
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