1998 Mercury Mystique Crankshaft Sensor

With only 90K on the car, let's not panic just yet. Did they clear the CPS code and it cane back again? Also, was there a driveability problem with the car before all this started? Please advise.

Problem started just after the brakes were repaired. At first it was only intermittently and only after the car warmed up. After the sensor was changed, the problem got alot worse. They could not clear the code (reason for changing the computer).She was able to drive the car about a mile from the dealership. Upon stopping at lights etc., the car would chug and sometimes stall. She drove it to an autoparts store and had them check the code : P0340 (same code after changing the sensor). She could not get it to run without giving it alot of gas and had it towed back to the dealership that changed the sensor, at which time they claimed the computer was the problem and replaced it.

Has changing the ECM solved your problem? Please advise.

No. We are still getting the same symptoms (chugging, stalling, P0340 code).

Out of curiosity, what did the dealer say after changing the ECM didn't solve your problem? Did they check fuel pressure and the EGR valve?

He said he didn't know what was wrong with it and to not spend anymore money on the car. To our knowledge, the fuel pressure and EGR valve were not checked. The car STILL has P0340 showing as the code. Is it possible another sensor is faulting and a false code is presenting?

It's not impossible the new sensor is bad. I just had a GM product with the same symptoms. He had a brand new CPS right out of the box from GM that was bad. One thing I have learned over the years is, believe the computer. Too many ECMs are changed out needlessly, because people didn't believe what they were telling them.

I doubt that faulty or bad new sensor was a possibility to the mechanics that are working on the car right now, otherwise they would have checked that before installing a new computer. Your advice is certainly something worth checking. I will pass this along to my daughter. I really appreciate you taking the time to help me with this problem. You've been very helpful! If we are able to find the exact source of this problem, I will certainly send it along to you and your readers!

Have a nice day!

The problem could be that a p0340 code is actually the camshaft position sensor and not the crankshaft sensor. Are you sure the right part was replaced?