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My 2003 T&C 3.8L Limited recently lost power when going above about 25mph. No Check Engine lights come on so far. I have narrowed the problem to the engine, which starts to sputter at around 2000rpm while gear shifted at Park, no matter engine cold or warm. I have changed spark plugs, spark plugs wires, PCV valve, throttle position sensor, MAP sensor, and the problem still exist. Last weekend, I replaced the fuel filter and measured the fuel pressure which is 54psi at idle or 2000rpm. Now I don't have a clue what to do next. Please help and thanks in advance.
 

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Did you clean the throttle body while you were working with the TPS? Checking the fuel injector wiring harness (behind exhaust crossover pipe) is free to do. The harness cover is velcro'd together. The wires in that location get hot, the insulation melts and wires can short together. If injector wires short together, it can trigger the injectors at the wrong time, or more times than normal, and cause a rich condition. It can also short out the transistors in the computer, requiring a new one if left for too long. It may be just starting to fail, and that's why there are no codes yet. If it gets bad enough, the TPS and MAP sensor wires also get shorted and you get codes for those.
 

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Did you clean the throttle body while you were working with the TPS? Checking the fuel injector wiring harness (behind exhaust crossover pipe) is free to do. The harness cover is velcro'd together. The wires in that location get hot, the insulation melts and wires can short together. If injector wires short together, it can trigger the injectors at the wrong time, or more times than normal, and cause a rich condition. It can also short out the transistors in the computer, requiring a new one if left for too long. It may be just starting to fail, and that's why there are no codes yet. If it gets bad enough, the TPS and MAP sensor wires also get shorted and you get codes for those.
Thanks Dan, will check the throttle body and the wiring harness this weekend. CK
 

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In park, Chrysler prevents the engine from going over 2000 rpm.

If you can check your fuel pressure while driving, as you might just have a clogged fuel filter or failing fuel pump. If you don't know when the fuel filter was changed, just change it.
 

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Thanks Dan, will check the throttle body and the wiring harness this weekend. CK
Did you clean the throttle body while you were working with the TPS? Checking the fuel injector wiring harness (behind exhaust crossover pipe) is free to do. The harness cover is velcro'd together. The wires in that location get hot, the insulation melts and wires can short together. If injector wires short together, it can trigger the injectors at the wrong time, or more times than normal, and cause a rich condition. It can also short out the transistors in the computer, requiring a new one if left for too long. It may be just starting to fail, and that's why there are no codes yet. If it gets bad enough, the TPS and MAP sensor wires also get shorted and you get codes for those.
Hi Dan, I checked the wiring harness yesterday. Pulled out the velcro and inspected the wires. I did not see any insulation melted and the wires were easily separated apart. Tested the car and it still sputtered. Today, I tested again and it went to 3500rpm without sputter when the engine was hard cold (parked overnight), then it started to sputter at 3200, then gradually drop to 3000, 2700, 2500, and 2200rpm while the engine warmed up in about couple minutes. Looks like it is temperature related, any idea?
 

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Hi Dan, I checked the wiring harness yesterday. Pulled out the velcro and inspected the wires. I did not see any insulation melted and the wires were easily separated apart. Tested the car and it still sputtered. Today, I tested again and it went to 3500rpm without sputter when the engine was hard cold (parked overnight), then it started to sputter at 3200, then gradually drop to 3000, 2700, 2500, and 2200rpm while the engine warmed up in about couple minutes. Looks like it is temperature related, any idea?
Problem solved finally. It was a blocked or restricted catalytic converter. I found it out by using a vacuum gauge to check how the vacuum changed while revving up the engine from idle to about 2000rpm. Also confirmed by removing the upstream O2 sensor temporary. Now the catalytic converter has been replaced and this baby is running normal again.
 

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That's great news. You stuck to it.
 

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Great job !
You did a great job by (especially) returning here and letting us know what you results and discovery are/were.

and good job at fixing your mini!

Welcome to the forum!
 
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