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MPMoore
MPMoore, GM WORLD CLASS/ASE MASTER W/L1 GMC
Category: GM
Satisfied Customers: 2851
Experience:  15 YEARS AS GM TECH, TEAM LEADER/SHOP FOREMAN AT A GMC DEALERSHIP
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2002 OLDSMOBILE BRAVADA: CYLINDER..VORTEC..MILEAGE..SERVICED

Resolved Question:

I AM THE OWNER OF AN 2002 OLDSMOBILE BRAVADA WITH A 6 CYLINDER VORTEC 4200 ENGINE. MILEAGE IS BETWEEN 96,000 AND 100,000 MILES. IT HAS BEEN SERVICED REGULARLLY. HOWEVER, I SEE NO RECORED OF AIR CLEANER REPLACEMENT, AND IT HAS THE ORIGINAL SPARK PLUGS.

THE ENGINE IDLES ERRATICALLY, HOWEVER, IT STARTS READIALLY, AND NEVER STOPS. AS SOON AS THE RPM'S ARE INCREASED IT SMOOTHS OUT AND RUNS NORMALLY. WHEN IT IS MOVING AT ANY SPEED IT RUNS VERY QUIETLY AND SMOOTHLY.

EVEN THOUGH, ACCORDING TO THE MANUAL, THE SPARK PLUGS ARE DUE FOR REPLACEMENT. IT SEEMS TO ME, IF THEY WERE BAD IT WOULD RUN ROUGH AT ANY SPEED?

A SLIGHT AMOUNT OF OIL SEEMS TO BE LEAKING THROUGH THE CAMSHAFT POSITION SENSOR. THE PERSON WHO SERVICES THE VEHICLE SAYS THIS SHOULD BE NO IMMEDIATE PROBLEM?

CAN YOU GIVE ME ANY INSIGHT INTO WHAT THE PROBLEM COULD BE?
Submitted: 5 years ago.
Category: GM
Expert:  MPMoore replied 5 years ago.
At what rpm does the engine idle at in gear when its warm??

Is it a rough idle or a vibration felt in the truck?
Customer: replied 5 years ago.
<p>ABOUT 600 RPM</p><p>ROUGH IDLE</p>
Expert:  MPMoore replied 5 years ago.
A dirty throttle body can cause a rough idle, When the throttle body is dirty it chokes the engine from getting air when at idle. The throttle body is easy to clean, should be done around every 30k miles.

A bad camshaft phaser solenoid could also cause a bad idle. This solenoid controls the camshaft timming. Sometimes the solenoid will leak oil out of the connector, if this is happening you will have to replace it.

You should check the air filter to make sure its clean, the filter can be hard to inspect. Some techs will not check it during oil changes due to its hard to inspect.

The spark plugs should be replaced, if they are bad it will cause a mis-fire. If they are worn it can cause a rough idle, the coils have to get move voltage to fire a worn spark plug(excessive gap) which causes the spark plug to fire late.

A dirty fuel filter would cause a lack of power, not a rough idle but should be replaced every 30k. Also you should have the injectors cleaned at the same time.

The picture below is the camshaft position actuator solenoid.


Object Number: 744600  Size: SH





MPMoore, GM WORLD CLASS/ASE MASTER W/L1 GMC
Category: GM
Satisfied Customers: 2851
Experience: 15 YEARS AS GM TECH, TEAM LEADER/SHOP FOREMAN AT A GMC DEALERSHIP
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