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Q: 3-5" of vaccum at idle. only 10-12" at@3000rpm....180-200lbs compression. on 1995 Pontiac Grand Am

no signs of vaccum leaks. head redone 1000mi. ago. fresh gas, good fuel pressure.pulled oxy sensor& ran. (bad convertor?) it runs the same.pulled p/b booster line &plugged no change...runs rough but will run..so whats wrong?
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95 grand am 2.3.... also cleaned plugs & drove 5 mi. no change...pulled plugs,all are black&sooty... put in NEW PLUGS... drove 5 mi. no change... new ones are also all blk &sooty
It's clear you have a valve timing problem. Your vacuum at idle should be at least 18 inches.
The timing chain has jumped. Stop driving this car. If you continue to run this engine you'll be looking for a differant car.
Have someone check crank to cam timing.
thanks for reply ...makes sense that timing is off.980 miles on new head job AND CLOYES TIMING SET.I HEAR these motors are common to blow head gaskets & jump time.so I thought I would buy a quality timing set.....oh well, with their lifetime warranty,I'LL send back &try another.thanks again for ur reply
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