Poor idling engine has new intake gasket,head gasket torqued to specs. new spark plugs, idle solenoids check good. Starts quickly, idles fine for about 10 seconds,but then goes to poor idling until it shuts down Runs fine at 1000 or higher rpm. Sometines increases speed on its own when above 1000 rpm

Pontiac Grand


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Vacuum leaks. Check hoses. Also check the intake manifold at the gasket. To check the intake (have the MAF plugged in) Spray some wd40 around the intake at the gasket seal. If the engine starts running fine at some point. Replace the intake manifold gasket.

have you gone over the throttle body and changed the idle position solenoid. They go bad and that acts like a cork , when it is stuck. It creates the air bypass , when you are idling. Take the intake snorkel off and look at it, clean it. take off the throttle body and you will be amazed at how much crud is under the butterfly plate. That crud gets into the throttle position sensor and the idle solenoid valve. I changed those sensors ( everything is $40.00 each for those ) and all idle issues went away. Have not been back for 2 years. Remember that fuel injected engines have an air pedal. it's not a gas pedal. If air is cut off at idle the computer can't compensate for it beyond a certain point. If it is running rough, then you also have to look at loose wires, spark plugs, head gasket integrity.

Timing chain ,marks right ?

Have you checked your engine coolant.
White smoke is a good sign of a blown head gasket or failed intake manifold gasket.
Check your coolant first and your oil.
Check oil and see if it seams over filled.
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Check vacuum leaks , by spraying carburator cleaner around intake manifold gasket and vacuum hoses connections . See if engine picks up the idle speed while you doing it , and if it does , locate leak and fix it. Most common , intake manifold gasket brakes.

Check the rpm gauge while running. If the RPM needle fluxuates while idling that is caused by a defective spark plug and or a spark plug wire

Vacuum leaks. Check all hoses and intake bolts. Leaking EGR or plugged PCV valve. Air filter plugged. Leaking head gasket. Worn timing chain. Camshaft lobes worn. Valves burned or leaking. Fuel idle control system or sensor. Good luck!

My problem was solved when I repaired my 4 wd activation dash switch. The switch was contacting on 2WD & 4HI at the same time. The front differential activation is vacuum activated possibly creating a tug of war that didn't actually engage it but drained off vacuum from the engine? A theory at best but stumbbled across it because I knew the switch wasn't working properly I repaired it and low and behold rough idle disappeared and all is good for 3 weeks running.

sounds like a fuel delivery problem. try cleaning carb.