Engine Mechanical problem
2001 Pontiac Grand Prix 6 cyl Front Wheel Drive Automatic 160000 miles
My engine is the non-supercharged 3.8L. I just replaced my upper intake manifold due to warping that caused a coolant leak. This included removing the fuel rail and cleaning most of the top side of the engine. After putting everything back together I discover that it seems like my engine is starving for air in the vacuum lines. When I remove my oil cap there is a ton of suction through the valve cover. From my experience this has something to do with the EGR valve being plugged or not working. Could you give me heads up on how this might have happened while I was replacing my upperintake? Is it possible that I could have spilled coolant into the EGR valve tube?
If you used ANY RTV sealant on the intake manifold gasket you may have clogged up some vacuum lines in the intake manifold.
The intake gasket should be put on dry after cleaning surfaces.
In any case I think you will have to remove the intake, clean it and replace the gasket.
I have seen some mechanics drill a small hole in the oil cap tube, but I would not.
EGR should not flow at idle, if it flowed it would cause engine to die.
January, 29, 2009 AT 11:20 AM
The gasket for the intake is a plastic piece that has a rubber insert so I did not use any extra sealant. I suspect you are right that I will have to take it off again which sucks but it will go twice as fast this time around. Would it be possible to get a bit more explanation as to how the vacuum system works and what it should be doing? It seems to me like something is plugged up somewhere.
January, 29, 2009 AT 11:30 AM
The MAP sensor gets vacuum from small lines in intake manifold for example.
Something has clogged a line somewhere, old gasket pieces etc.
I have seen this same symptom, where there is a LARGE sucking sound when you remove the oil cap.
But this guy coated both sides of the gasket with RTV. In this case the intake manifold had to be replaced, because the RTV had clogged up the passages so bad I could not get it out.
I would remove the manifold and blow out ALL the passages with compressed air. Make sure feel the air come out the other end.
January, 29, 2009 AT 6:13 PM
Not to step on your toes but I am sure glad I didn't take that whole upper intake off again. I was missing the bottom o-ring on the PCV valve. The new UIM came with the top o-ring for the PCV valve but not the lower o-ring. I didn't think to check it. Thank goodness its easy to get to. So for anyone who may have come across this issue by searching for it, Check your o-rings on your PCV Valve.
January, 29, 2009 AT 9:27 PM
Good catch. The disadvantage we have is not being there, but I'm glad you found it. Mmprince4000