My engine is a 5.0 high output with automatic transmission. When engine is cold, car runs fine. After reaching operating temperature, and driving one mile, it begins to lose power at 1200 rpms and it bucks, hesitates, and backfires through exhaust. The engine will never die, and still idles good. I have replaced the spark plugs, ignition coil, throttle position sensor, and engine coolant temperature sensor, and have not been able to pin down the true problem. Would appreciate any input, also, no engine check light come on. Saundra
How many miles are on the car?
Could be a pluged cat.
If you shut it off after the problem do you have a hard time starting it again?
The car has 159,000 miles external temperature of the cat is 400 degrees F, and the car does start back easily with no problems. Thanks for helping us. Saundra
You said it has no check engine light, but has it been scanned for codes???
Sounds like it having problems when the EEC enters closed loop operation. Its a good possibility the sensors in the MAF meter are dirty. They can be cleaned by removing the two torx screws(they are anti-tamper type, so they'll require a special hollow bit), and CAREFULLY cleaning the sensor wires with a Q-tip and some alcohol.
Good advise, thank you for helping. We are going to clean the maf meter this weekend, replace the distributor cap and rotor, along with the plugs. We are also going to have a go at reading the code from the ecc. Will get back to you all with our results. Saundra