Question about Pontiac Bonneville
This sounds like 1 of 2 possible problems.
a bad headgasket or a clogged catalytic convertor. i would lean more towards the convertor
Posted on Jul 16, 2008
Make sure that there are no obvious small diameter hoses that are torn or collapsed. look at the pcv valve area because of oil saturation and especially at the map sensor to make sure it is both plugged in and that the hose or mounting point at the intake is not at fault.... vacuum leaks cause lean codes and hesitation...
more hazardous to your engine is pinging and heating issues which could cause damage to the catalyst... could get expensive once the o2 sensors and cat go bad...
only other guess i can offer is fuel pump not putting out enough pressure but i would suspect a vacuum leak because of the hissing and symptoms you have described
Posted on Jul 28, 2012
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