Questions and Answers

Caviler Loses Its Cool Q. I have a 1986 Chevy Caviler 2.0 liter TBI and five speed transmission with two problems; the electric fan will not come on and it idles to fast and misses some at all different speeds. I drive it to work 106 miles a day and it acts up but has never stranded me. The check engine light has come on during some of these fits.

The codes I got testing it are the prom in the ECM is bad and the ignition module or ECM is bad. Both of these codes in the Haynes book recommend taking the car to the dealer. I have replaced the following items trying to fix this problem and had no luck. I have talked to many parts people and everyone says the prom never goes bad and if it is the dealer might be able to get one but does not think he can.

For the fan:
Tested fan, good.
Replaced fan relay (old fan relay case busted closed contacts fan runs).
Replaced coolant sensor two wire one in thermostat housing.
Replaced ECM.
No luck car only over heats when idling.

For the idle:
Replaced ECM.
Replaced O2 sensor.
Replaced map sensor and checked or replaced vacuum lines.
Replaced ignition module in distributor.

Items I suspect but have not replaced:
Throttle position sensor.
TBI base gasket.
Intake manifold gasket.

I have the original ECM unit back in the car but the fan and idle did not change with the new one but I had to the old prom in the new ECM. The car's old but has only 60,000 miles on it.

Any help would be great. Thanks in advance for any advice you can give.

A. Okay, we have a good cooling fan, a good cooling fan relay. I'm going to assume you replaced the correct cooling fan sensor. It is a two wire connector, one yellow wire and one black wire, and we have a good ECU

Since the components are okay, we have to look at the wiring. There is a black/pink wire that goes from the cooling fan relay to the cooling fan motor. A good way to test this is to jump the red wire to the black/pink wire and see if the fan runs. If it doesn't, then there is no power to the red wire or the black/pink wire is broken between the relay and motor.

If that checks out okay, check for a 5-volt signal at the yellow wire on the cooling fan temperature sensor. If you have no signal, the yellow wire between the sensor and ECU is broken. If you have signal, then check the black wire, you should have continuity between terminal A11 at the ECU and the sensor. If not, the ground wire is broken.

In addition, make sure the 20 amp C/H fuse (#17) is good and that there is power at the brown/white wire of the cooling fan relay.

Additional Information provided courtesy of ALLDATA