ECU for Jeep Cherokee

I disagree... 300rpm is not normal... I feel that the idle air solenoid is closing down when he opens the throttle, then motoring back up after the throttle hits the closed stop. This certainly points to a TPS problem.... let's see what happens after he performs the TPS alignment procedure you gave. __ Steve .

reigelser did pass the time by typing:

As much as I don't like throwing parts at a problem you might want to try the MAP sensor before the ECU. When it comes to paying out $450 it's also a good idea just to take it into a dealership and have them do a full diagnostic on the engine.

I've gone through two MAP sensors and the symptoms are usually some stubling along with a gutless acceleration except when the gas is floored or when the engine is running in warmup-mode.

Just for grins, check the O2 sensor lead as it goes up the front of the block and make sure it's not melted or abraided. This can cause headaches to the ECU.

Here the full story:

The enginelight came on about 6 weeks ago. Evaluation with the OBD reader showed a P0123. So I replaced the TPS. While doing that I stripped a thread on the throttle body. The tps was fixed with one screw, the error was still there. I found a god throttle body on a junk yard and replaced the existing one. The one from the junk yard came with all sensors (MAP, TPS and Idle Motor) and the problem was exactly the same. All Voltages measured right, error code P0123. So I got a new ECU from the junk yard and put it in. Same exact error message, not resetable P0123. I put the old ECU back in and gave the ECU back to the junk yard. Then I gave the car to the mechanic who did some troubleshooting and told me its most likely the ECU. When I told him I replaced it allready, he mentioned that on some vehicles (he had problems with chevy ecus) a reprogramming is required that just the official dealers can do. A new ecu for the jeep is 480$ approx. As you could see in the newsgroup I followed the advice and checked all electrical connections, measured the common ground and the grounding of the engine block, cleaned the contacts and did reteaching of the ecu.

The driving is not bad with the car. It starts at 2nd try always, in the beginning with the old throttle body it would stall when it was cold, but now it doesn't anymore. When the engine is cold the first couple of hundred yards it runs a bit rough (throttle response is slow)but then it just jumps a little bit for example on the high way when accelerating from 65 to 75 with little gas. There seems to be one position of the gas in that regime where it almost goes into a resonant oscillation (difficult to explain, it feels like going on and off the gas in 0.5 sec distance even though the throttle isn't moved at all).

If you have any additional ideas and good advice that would be highly appreciated. I want to make sure to do everythiong possible before I put the car to a Jeep dealer.

Thanks

Joachim

Hi, the problem is solved. 2 days after I sprayed everything with contact cleaner, the error went away by itself. That was 4 days ago. Self healing Jeep. Let's see if it stays like that.

Thanks for all the help and advice.