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1993 1.8L cold start issue


IdahoRodeo
11-14-2011, 10:28 PM
I have a 1993 corolla that runs fine once warm. The problem is a cold idle problem. When starting it cold, it dies unless you feather the throttle. I can keep it running by feathering the throttle until it warms up. Once warm it runs fine. If I let off of the throttle at all during the warmup period, it dies instantly. How does the choke work on these vehicles? Could it be a IACV problem? Anything else it could be?

jdmccright
11-16-2011, 11:13 AM
I would definitely check the Idle Air Control (IAC) valve for operation. You can remove and spray the mechanical plunger to remove any build-up, but don't try to compress the plunger. If you do you could break the servo motor or small teeth that move the plunger. And don't spray the electrical portion that is outside the throttle body (TB). Also spray down the plunger seat in the TB.

Another possibility is the engine coolant temperature (ECT) sensor is faulty. This can make the engine's computer think the temp is hot when it isn't. Test for continuity and correct operation...it's located just before the uppper radiator hose connects to the engine.

IdahoRodeo
11-16-2011, 01:39 PM
What is the typical resistance value I should read? 1-10 ohms or something like that?

Brian R.
11-16-2011, 02:30 PM
Test the resistance hot and cold. There should be a significant difference between them. Although I don't have a manual for the engine, a Camry 4-cylinder engine would have resistances of 2-4 kohms cold and around 0.2-0.4 kohms hot.

IdahoRodeo
11-18-2011, 02:34 PM
Checked the resistance. Hot it gets to .4K, cold it will get to 5K. Seems to be OK. On a side note I pulled the connector off and stuck a 4k resistor in and the idle kicked up to 1400 like I would expect. Put it back on the Temp sense and it still ran horrible. Once the car is warm I noticed that turning on the lights the idle drops hard and struggles to recover. It eventually does though.

Brian R.
11-18-2011, 06:36 PM
Your experiment with the resistor seems to indicate the ECT sensor or connector is the problem. If the ECM was seeing 4 kOhms from the sensor, the engine would run like you saw it run with the resistor if the engine was cold. Double check the connection to the sensor. It may not be making a good connection - corrosion, bent parts in the connector, etc.

Do you have a cold-start injector? If so, there are 3 or 4 parts in that circuit that could cause this problem.

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