Engine trouble

[Bushwack]

I’ve asked for assistance in the Reatta forum but have run into a wall and I’m hoping someone here has some advice regarding an engine problem.

When driving my ’90 Reatta a minute after a cold start until a couple minutes AFTER the car reaches normal operating temperature (195*), the engine will idle at 1500-1700RPM until I come to a complete stop. It will then drop to 750RPM (normal).

For example, I will drive down a street going anywhere from 5 – 40MPH. Half way down the street, I will put the tranny in neutral and the engine will be at 1500-1700 RPM until I come to a complete stop. If I stay in drive, I can feel the car accelerating as I come to a stop; putting more effort into braking and making it difficult and dangerous. Also, with the car hot and running normally, I can turn the ignition off and on within a couple minutes and the problem comes back but goes away after driving a couple blocks.

There are no error codes showing and running the ECM with the car idle or moving, cold or hot, all the readings are within their respective parameters. So far, I have replaced the IAC, TPS, O2 sensor, new thermostat and coolant sensor, PVC grommet and I have had the fuel injectors cleaned. Plugs and wires are good. There are no vacuum leaks and the intake gasket is good.

I would appreciate any advice/suggestions on how to get this resolved. I'm perplexed as is my mechanic and the Reatta forum folks have run out of ideas.

Thanks.

[bb1970]

Throttle position sensor ?

[Bushwack]

Throttle position sensor ?

TPS was replaced.

[1965rivgs]

Have your mechanic connect a scanner and watch the displayed engine temp versus actual engine temp. Sounds like a coolant temp sensor problem...and it doesn`t matter if it has already been changed and is "new". Good luck,

Tom Mooney

[Guest Steeleco]

I had an idle problem with a car once that had to do with vacuum and I think it involved the brake booster. Just a thought.

[Bushwack]

Have your mechanic connect a scanner and watch the displayed engine temp versus actual engine temp. Sounds like a coolant temp sensor problem...and it doesn`t matter if it has already been changed and is "new". Good luck,

Tom Mooney

Thanks for the suggestion but I'm not sure what good that would do? Both before and after the coolant temp sensor was replaced, the engine temperature was OK. Car would warm up normally and reach temp as it should (I have another Reatta to compare it with and both work as they should regarding reaching 195*). If I was to leave the car idling until it reached normal temp, you couldn't tell there was a problem. It's only when I place the car in drive does the car act up.

[Guest pfloro]

At this point, I would replace the ECM itself. Considering the diagnostic work which you have already done, I sense that the ECM is flaky.

I believe that 'remanufactured' OBD I ECMs are under $100 (but I'm not sure).

Although not directly related, I had a problem with the original ECM in my '84 Toronado after it was about 12 years old. The engine would lose power and go into open loop on an intermittent basis. No codes were set nor did the Check Engine light ever illuminate. After checking sensor connections and measuring some voltages, I tried a 'remaned' ECM. That solved the problem. I determined that for some reason, the old ECM would stop providing the EST (Electronic Spark Timing) signal to the HEI ignition module. This caused the loss of power.

Keep us posted,

Paul