Also, I wonder how a bad CKP sensor could only be intermittently bad at idle only…
Yes, George San Jose! I. Held a thin piece of paper behind the tailpipe and at times it was definitely being sucked into the tailpipe. So now I suspect a sticking exhaust valve. Can you recommend an effective chemical treatment? Ive tried Lucasoil and Seafoam gas treatments with no improvement. Should I try an oil additive next?
Add Seafoam to the oil.
Tester
Yet now I just happened to think…here comes that irritating phrase “intermittent malfunction” again-my compression check showed readings of 150 to 158 psi in all the cylinders. At the time of the test, no exhaust valves sticking apparently
Thanks for recommendation of Seafoam for oil, Tester.
If a dollar bills seems to get sucked into the tailpipe at times, that means something of a serious nature is definitely amiss. But not necessarily a valve problem. I wouldn’t make that assumption unless you have other reasons to believe there’s a valve problem. Could be a simple misfiring problem, check for common causes first. )
Common causes of misfiring
- Spark plugs (check for carbon build up on tip and gap spacing)
- Coil(s) — (difficult to diy’er test)
- Coil electronics not getting proper trigger signals (wiring or ECM problem)
- Fuel injectors not getting pulsed (noid light to test)
- Fuel injectors not injecting correct amount (difficult to diy’er test)
- Crank position sensor fault (wiring between sensor & ECM, or sensor faulty, usually when these fail, it’s due to heat, & engine won’t run at all. I’m doubtful of this as a cause.)
- Compression problem
Suggest you diy’er test the things you can. If nothing found, ask shop to test the ones that are diy-er unfriendly. Good chance they’ll find what the problem is, then you can replace the failed part(s) yourself if you like.