Engine Mechanical problem
1996 GMC C1500 V8 Four Wheel Drive Automatic 169000 miles
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I have a 1996 GMC with a 350 and there is Excessive Crankcase Vacuum and the Idle is high at 2000 rpm, there was only one code for a misfire on cyl 4.
When I checked that one there was a good amount of deposits on it. I did a compression check with all being around 165 lbs except for that one which was slow to come up to 165 lbs. If you take off the oil fill cap when its running (if it dosn't pull it out of your hand) it just about goes to a stall.
Any help would be appreciated

Thanks

Have you checked the PCV valve? it may be broken or stuck