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Mystery missfire & oil leak

War97gtp

New member
97gtp 65k miles. First the missfire: Only happens at idle and only missfires about once every 5 seconds (hear a slight pop from the exhaust) otherwise runs perfect. No engine light changed plugs, wires coils are newer msd coils, but were swapped with known good coils to test (from another 97 gtp i have) none of those helped. Here is what i think it might be I noticed that only under idle the hvac controls dont function correctly for example: if its set to "vent" position and you change it to "floor" instead of blowing only from the floor its like 60% floor and 40% vents and once you start driving it goes to mostly floor. This happens on the other selections as well (defrost, floor, and vent) you set it to one position and it blows out of there and somewhere else as well.
Are the hvac controls vacuum operated? my guess is if they are there is a tiny vacuum leak somewhere with one of the vacuum hoses that runs to the controls, causing not only the missfire at idle but also not enough vacuum to properly operate the hvac controls.

2nd the oil leak: it seems to be the same exact leak in both of my 97gtp's but i cant trace it down the only thing i can confirm is that oil pools in the lower passenger side motor mount bracket (near the front passenger side wheel), unfortunately this also destroys the rubber motor mount (oil eats rubber).
 


Oil pan gasket or the lower front cover corner is leaking. You'd end up fixing both if you did the oil pan gasket as you should put new RTV there.

Yes the HVAC is vacuum assisted, the middle vacuum line on the supercharger vacuum tree leads down into the firewall and into the cabin.
 
Oil pan gasket or the lower front cover corner is leaking. You'd end up fixing both if you did the oil pan gasket as you should put new RTV there.

Yes the HVAC is vacuum assisted, the middle vacuum line on the supercharger vacuum tree leads down into the firewall and into the cabin.

front cover as in valve cover gasket?
 
Of course, the crank seal! why didn't i think of that makes perfect sense now the crank seal is directly above that motor mount bracket, thanks for tuning in Bosquegtp98.
 


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