I was checking out my Sister-in-Law's car, a 1987 Olds 98 with a 3.8, it looked as though the cap wasn't seated fully, so I unscrewed it. The engine stalled immediately! I have never seen this before, have you? What could cause this? Does it create a major vacuum leak, and if so, why doesn't it seem to have any effect on my car?

Thanks in advance!

Ken

 

Welp, the PCV valve might be bad on your sister-in-law's car. PCV; positive crankcase vent; works on vacuum. When there's enough vacuum in the PCV hose, the PCV valve opens, and the vacuum in the hose will suck crankcase fumes out of the valve cover.

I'm going to "guess" that your sister-in-law's PCV valve is old and stuck "open", and that by popping the oil fill cap off, you created that vacuum leak you guessed at. On your car, the PCV valve is probably good, meaning the valve is shut at idle, meaning there's no vacuum leak.

Try this- engine on, pull oil fill cap, make sure the car stalls. With the engine off, put the oil fill cap back on. Remove the PCV valve from the valvecover, and put your finger over the valve. (Note: put your finger over the end of the PCV valve, not the hole left in the valvecover). Have someone start the engine. When it starts, remove the oil fill cap, see if the engine stalls. If it doesn't stall, remove your thumb from the end of the PCV valve and see if the engine stalls.

And let me know if I helped; I'd love to know if I guessed right!


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

Hi Tom,

You will have to wait a bit to find out if you are right. The car is in South Carolina and I'm back in Florida. I plan to go back in a few weeks though, and I will test your theory then!

Ken

 

Heh, no problem, just let me know!


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!