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Re: boostless detonation... Posted by Ari [Email] ![]() ![]() In Reply to: boostless detonation..., JG, Thu, 10 May 2001 20:38:29 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Exactly what the others are saying, plus a few others-
Timing too advanced
Bad Air Mass Meter
Running too leak (vacuum leak, weak fuel pressure regulator, bad O2 sensor)
Old spark plugs
Too low an octane fuel
Carbon buildup in cylinders
....
It sounds like some massive preignition going on there. The O2 sensor has only limited capability to adjust mixture (25%) - but the Air Mass Meter (AMM) has full authority (100%).
First, check your timing. It may be WAY off. Rev the engine and see how the timing changes - there may be a problem with the centrifugal advance/vacuum retard system.
Next, pull the spark plugs. Do they look a nice greyish-white (unlikely), or are they white with chunks of crap stuck to them? If they're white, that indicates a lean mixture. Are they the right temperature range? Peer into the cylinder with a flashlight - do you see a little carbon on the top of the piston (normal), or is it all caked up?
If you're running lean, start checking for vacuum leaks. Hoses may be cracked or split, especially near the ends, or one may have just fallen off.
Beyond this, you may need some professional help, depending on your skill/experience level. Have the fuel pressure regulator checked for pressure and delivery rate. Have the AMM checked (usually by swapping out for a known good one), but a decent mechanic should be able to trace down a lean running issue.
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