Join Date: Jul 2006
Location: Des Moines, Iowa
Time for a new head gasket?
After 15 years of relatively trouble free ownership, I've been chasing a poor-running condition in my '85 Graduate all summer. Symptoms are:
- poor idle, engine vibration
- low power, especially below 3k rpm
- backfire on aggressive throttle
- starts fine, hot or cold
I worked though Greg Gordon's excellent L-Jet diagnostics: checked vacuum leaks (new silicone hoses), cleaned grounds, new plugs cap and rotor, checked L-jet switches and sensors, had injectors cleaned by OKInjectors. No joy.
I finally got around to a compression test:
Cyl 4: 140 psi
Cyl 3: 136 psi
Cyl 2: 145 psi
Cyl 1: 0 (This could be the problem!)
No trace of coolant in the oil or oil in the coolant, but there is positive pressure in the valve cover. Valve timing seems to be right on, but when I take the oil filler cap off I get a lot air blowing out. That ain't right, is it?
So do you think I'm looking at my first head gasket project here, or could this be something else? Rings? Cracked head? Leaky valve? Any other tests I should do while its still running or do I just take the head off and see what I find?
Thanks for any advice on how to proceed!
85 Alfa Graduate