Rough idle, missfire codes

[Cadillac Tech]

Document ID: 2168116

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#08-06-04-038: LC3 4.4L Supercharged Engine Hard Start, Miss, Misfire, Idle Rough, MIL/SES Light, DTCs P0300/P0301/P0302/P0303/P0304/P0305/P0306/P0307 or P0308 Due to Fuel Fouled Spark Plugs (Replace Spark Plugs) - (Jul 16, 2008)

Subject:

LC3 4.4L Supercharged Engine Hard Start, Miss, Misfire, Idle Rough, MIL/SES Light, DTCs P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 or P0308 Due to Fuel Fouled Spark Plugs (Replace Spark Plugs)

Models:

2006-2009 Cadillac STS-V, XLR-V

with Northstar® 4.4L Supercharged V8 Engine (VIN D -- RPO LC3)

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Condition

Some customers may comment on a hard start condition, rough idle, miss and or misfire with the MIL/SES light illuminated.
Upon further investigation, technicians may find DTCs P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 or P0308.
This may be experienced on vehicles that have repeatedly been driven short distances without reaching operating temperature. This condition is most likely to occur when the vehicle is still a dealer stock unit or when the vehicle arrives at the dealership on the transporter. This condition may also occur if the car is driven for short duration trips.
Cause

This condition may be caused by the engine not reaching operating temperature before turning off the ignition.
Correction

To avoid this condition, run the engine until the coolant reaches operating temperature. DO NOT attempt to clear fouled spark plugs by running the engine at a higher RPM - doing so may damage the catalytic converters.
Spark plugs that are still fouled should be replaced with P/N 12592619. Refer to Spark Plug Replacement in SI. Clear any DTCs stored in the ECM.
Important: In order to prevent a reoccurrence, allow the engine to reach operating temperature before turning off the engine and returning the vehicle to the customer.
Parts Information

Part Number	Description
12592619	Spark Plugs, (A/C DELCO® #41-991) Platinum Plug
12345579 (U.S) 10953481 (Canada)	Dielectric Silicone Grease

Warranty Information

Am I reading this right? Is GM saying they were seeing fouled plugs on cars within the first few miles. i.e., during transport, started for movement around the dealership, or trips to the corner market??

[cubby558]

Mark,
It seems to be with the V's. Bruce told me this long ago when I bought my V. He said the engine and supercharger needs to get up to temperature and that short trips and or just starting it i.e. to back out of the garage is damaging. I haven't had any problems, but I let it run for awhile when I start it, just to make sure.

Originally Posted by mswaim

Am I reading this right? Is GM saying they were seeing fouled plugs on cars within the first few miles. i.e., during transport, started for movement around the dealership, or trips to the corner market??

[Cadillac Tech]

Originally Posted by mswaim

Am I reading this right? Is GM saying they were seeing fouled plugs on cars within the first few miles. i.e., during transport, started for movement around the dealership, or trips to the corner market??

Mark, not so much to the corner market, the engine would probably reach closed loop operation by then; but they did see a plug fouling condition ( & catalytic converter damage) when the engines were ran for just a few minutes and then shut back off...repeatedly. We saw this when the V cars (XLR & STS) were new or delivered during the cold months. A lot of sales people who would start them up to show customers; rev the engine and shut them off. Owners would do the same when showing off the new car to their friends.
The best thing to do is let the engine reach operating temp., drive it if you can, before shutting off the car.

Now it makes sense; kinda like all the dead batteries from folks wanting to show off the retractable hard top feature, with the car not running......


Not sure how the V's are delivered, but Ford found an interesting work-around to the problem of dealer lot abuse on the Shelby's S/C'ed engines.

Here is an excerpt from the GT500 owners manual:

"Alternate calibration Your Shelby GT500 power train control module (PCM) strategy contains a feature to limit supercharger boost pressure and engine speed to 4,000 rpm for the first five consecutive miles of vehicle operation or 50 engine start/warm up cycles. This feature is enabled prior to shipment. If neither of these conditions have been satisfied prior to customer delivery, full power will not be available."

The SCT prepped tune I am running on my car allows me to reset the "valet" mode and keep it in place until removed with the hand-held tuner, for situations where the car may be exposed to abuse by other drivers. Never used it, but it was offered when they tuned the car so I figured what the heck.

[mtrocket]

Originally Posted by mswaim

Now it makes sense; kinda like all the dead batteries from folks wanting to show off the retractable hard top feature, with the car not running......


Not sure how the V's are delivered, but Ford found an interesting work-around to the problem of dealer lot abuse on the Shelby's S/C'ed engines.

Here is an excerpt from the GT500 owners manual:

"Alternate calibration Your Shelby GT500 power train control module (PCM) strategy contains a feature to limit supercharger boost pressure and engine speed to 4,000 rpm for the first five consecutive miles of vehicle operation or 50 engine start/warm up cycles. This feature is enabled prior to shipment. If neither of these conditions have been satisfied prior to customer delivery, full power will not be available."

The SCT prepped tune I am running on my car allows me to reset the "valet" mode and keep it in place until removed with the hand-held tuner, for situations where the car may be exposed to abuse by other drivers. Never used it, but it was offered when they tuned the car so I figured what the heck.

I'll bet the Valet drivers wonder what the he** is wrong with your Shelby... they can't get the tires to turn turn over...

On the 2nd generation Lightning trucks, Ford used a waste gate on the S/C that when over-revved opened and dumped boost. Made for some red-faced burnouts when you hit the limiter and you lost 100 horse power in a blink of an eye...... Didn't take long for owners to figure out how to bypass that sucker.

[Cadillac Tech]

[QUOTE=mswaim;28359]Now it makes sense; kinda like all the dead batteries from folks wanting to show off the retractable hard top feature, with the car not running......

Low system voltage @ start up or cranking would also compound the engine overfueling problem.