'04 Duratec 46K miles, hesitation/stumble problem...

[jfl330]

Within the last 1,000 miles, the car seems to hesitate/stumble on the highway, its faint but I am sure its there. Also, mpg dropped off by about 3 mpg since this started.
Starts and idles fine.
Once and a while, stopped at a light, all the a/c and radio controls will blink a dozen times or so, and the car will shake. The after 20 - 30 seconds it stops and all is well.
The a/c compressor will kick out sometimes while on the highway, it will hesitate/stumble noticeably just before the a/c stops blowing cold.

Ideas?

[shorod]

My first guess would be a bad coil pack. The Duratech uses Coil On Plug (COP), correct - one coil for each cylinder? A bad coil (pretty common) will cause a misfire which has symptoms similar to what you describe.

Not sure about the electrical system issues you are experiencing though. You may want to first make sure the battery connections are clean and tight. Also check for damaged or loose vacuum lines.

-Rod

[jfl330]

Originally Posted by shorod

My first guess would be a bad coil pack. The Duratech uses Coil On Plug (COP), correct - one coil for each cylinder? A bad coil (pretty common) will cause a misfire which has symptoms similar to what you describe.

Not sure about the electrical system issues you are experiencing though. You may want to first make sure the battery connections are clean and tight. Also check for damaged or loose vacuum lines.

-Rod

Rod -

Last week I got a pending codes of P0351-6 which is related to the coil packs. But all of them bad simultaneously? Can the coil packs be tested, individually?

Could a bad battery have anything to do with it?

Jon

[shorod]

If the car's PCM is not seeing a reliable voltage, above 10.5Vdc, it can cause unreliable performance. Processors can go into reset, circuits can oscillate, etc. If you think you have a weak or bad battery, start there before investing a bunch of time and money searching for other problems.

It would seem odd that all 6 cylinders would indicate out of tolerance misfires. However, there is a code of P0300 for misfires detected, unknown cylinder.

If you can find someone with a higher-end scan tool that can display "component parameters" for the I/M Readiness tests, you should be able to monitor misfires on individual cylinders to help make sense of the P0301 through P0306 codes.

-Rod

[way2old]

Look at all the wiring going to the coils. if all wiring and connections are good, more than likely it is the PCM. Do as Rod suggested first. Also be sure the wiring harness is not close to anything that may cause rf interference.

[jfl330]

Originally Posted by way2old

Look at all the wiring going to the coils. if all wiring and connections are good, more than likely it is the PCM. Do as Rod suggested first. Also be sure the wiring harness is not close to anything that may cause rf interference.

Would an XM radio with fm modulation interfere?

[way2old]

Shouldn't. Unless wiring is somehow run close to the PCM wiring. Did installation and problem coincide ?

[jfl330]

Originally Posted by way2old

Shouldn't. Unless wiring is somehow run close to the PCM wiring. Did installation and problem coincide ?

Not really, had the XM for 3 - 4 months now. I think I'll go over to Advance Auto and let them check my battery/charging system.

[mjarmento]

We have pretty much the same problems with our 2004 Taurus Sel Wagon. Two Ford dealers have not been able to fix it.

I did notice the when I installed a new battery the problem went away for a good while. I now (monthly) clean the battery terminals and connectors really well and coat them with dialectric grease. So far it is working.

Hope this helps

Mike