after someone answers, I will explain more. Thanks

 

Yes, any one or more of these:

P0300
P0301(71)
P0302(72)
P0303(73)
P0304(74)

P1399 (temporary)

 

well, here is the deal...

The car has had the "low" rough idle that I think many have complained about. It has been doing this since August about 30% of the time I drive it (daily driver). I finally went to a different dealership because my old one just keep looking at it and saying "I don't know what's wrong".

Mechanic says that it is "missing" quite frequently (7 times on his 16 miles test drive). This car has 24,000 miles and has never thrown any sort of code. So far this week, they actually took the valve cover off, inspected the valves and retainers. He did not see anything yet so he was going to log (ODBII) all parameters when this is happening and send them in to the tech line.

Could it be an ECU problem if no codes are ever thrown? Or do you think he is miss diagnosing the problem?

And also, if the car has been misfiring for 10 months and 10,000 miles, do you think there could be engine damage from this (if not the motor mounts after running like a model T all this time).

 

*Yes, this is possible. Another member reported a couple years ago of similar symptoms. They did all kinds of things without success, till they put in a new ECU. Then, all was well. Now, this is NOT saying you have the same situation. You might have a MAP situation. You might qualify for the new TSB on the MAP and sensor securing system. Have you tried the ?MAP whack"? If this works, it might be an indication that something is wrong with your MAP sensor.

**This can only be answered after some close examination. A compression and leak down test might be very revealing. The engine mounts can be visually inspected.

 

If the Tech is talking to AHM techline, They will get it fixed. It make take awhile, But it will get fixed.

The Misfire monitors are fairly accurate, but not an absolute. Other problems can cause the engine to run horrible and NOT throw a misfire DTC. I'd wait for the Dealer's diagnosis before going any further.

 

Just as a reference....

- Map Sensor replaced (TSB with harness)

- IAC Valve replaced

- Map Whack

All made no difference along with the ECU reset

 

The low/slow to compensate idle speed may be normal. Every S I've ever been in is slow to react to temperture changes, and AC load at idle.

 

I have had the same symptons, however also a lit MIL (blinking check engine lamp) and therefore the error code (only one cylinder).

Rather than 'real' misfiring, it turned out to be as simple as a clogged fuel injector. Adding fuel injector cleaner to my tank of gas solved the problem.

I'm definitively not trying to tell you that this is your problem too, but keep it open as an option.

Good luck!


Siepel

 

I also tried running a bottle of techron injector cleaner in about 2000 miles ago just before the last oil change. Did not make any difference. Weird... I know.

I almost always use Chevron 93, from different gas stations.

 

Update-

Talked to Marcelo (mechanic) last night. He said that he drove it again with the computers hooked up and that it is misfiring on all cylinders. Right now he is not sure what the problem is.

Said he plans on pulling the cylinder head Monday. I'll keep you informed.