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My 94 Metro 3cyl. will not come off high idle. No vac. leaks, replaced coolant temp sensors (2), tried to adjust tps. no luck there. Timing is correct, car runs great, just won't idle down. Anybody have any thoughts?
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A few things to check would be the coolant temp sender, TPS sensor and last but not least check for a vacuum leak. These are just a couple things off the top of my head.
Your going to have to do some wiring tracing. You need an ohm meter. Since you still get a reading with the tps unplugged, you have a shorted wire or the ECM could be bad. The ECM is under the air filter. Unplug them both and check the wires for short to each other. The ohm meter shouldn't show a reading. If it does, you found the problem. Also check those wire for short to ground. Since the map sensor is right there I would also check the tps wires to the map wires for a short. Again there should be any readings. If all the wires check OK, then I would be looking at an ECM replacement.
Its most likely a vacuum leak or the throttle needs to be adjusted. Check that there is a small amount of play in the throttle cable between the bracket on the back of the intake manifold and throttle body. If there isn't, the throttle body may not be closing all the way.
Other possible causes:
The coolant temp. sensor is giving an incorrect reading. When the sensor reads a low coolant temp., like when you first start the car and the engine is cold, your idle will be high. As the engine warms up to operating temp (about 200 F) the idle speed will decrease. Idle speed should be around 750 rpm when the car is fully warmed (800-850rpms fully warmed with a/c on).
There no adjustment for idle, control by computer, TPS reading should be .50 volt's, you could have a vacum leak, check vacum line and check for vacum leak at base of intake manifold.
Unless you have replaced the hood or the sticker has been removed, there should be a label on the inside of your hood that lists the correct timing.
Make sure you short the two appropriate wires in the 'test plug' before setting the timing. It's on the drivers side firewall under the hood. The idle on 94 Metros is automatically controlled so you don't have to worry about setting the idle before adjusting the timing. My 94 automatic metro says 5BTC.
You might also check the single injector, had a friend's that the fuel pressure regulator had been messed with and was over-pressurizing the injector, that weakened the injector allowing it to flood at idle and also when cut off (the injector was leaking)
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