Re: Chasing Rough idle...compression?

Posted by fred kanter On 2011/5/20 15:08:27

Atmospheric pressure is about 15 psi, 8:1 comprssion would yield 120 lbs approx. Although your compression is a bit low it does not vary enough in my opinion to cause rough running. You seem to have rounded up all the ususal suspects but there are more things to check.

The distributor has been switched and the plugs are clean, but that does not rule out an arc jumping on the inside of the cap or plug wires either arcing to ground or to each other. All of those would give the symptoms you are experiencing.

LOw compression would compromise engine power.

Look again at a manual for other ideas.

Good luck