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Re: knocking Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Fri, 27 Jun 2003 05:31:38
In Reply to: knocking, sam, Thu, 26 Jun 2003 22:38:22 Members do not see ads below this line. - Help Keep This Site Online - Signup |
You don't mention what octane fuel you're using. The higher the octane rating, the less prone to knock. You may need to run higher octane fuel.
As cars age, some can get away with lower octane fuel, and some require higher octane. It's possible that you have carbon buildup in your cylinders, which increase the compression ratio. There could be some hot spots in the cylinders causing detonation.
Retarding the timing will help some with knock, but as you've noticed, kills the low-down power. Not fun in a NA automatic.
First, I would go back to the stock NGKs. Actually, run a grade cooler. You've got an ignition problem - now isn't the time to mess around with plugs. Not as much an issue with non-DI cars, but it's best to limit the variables.
Knock can be caused by lean running. How did the spark plugs look when they come out? They should be a nice light grey. If they're white, and especially if they have burned deposits on them, then you're running lean. This can be due to vacuum leaks, misadjusted AMM, clogged fuel or air filter, bad fuel pressure regulator (FPR), or shot O2 sensor. Probably a combination of a few.
Go with fresh NGK plugs, one range cooler. Make sure they're gapped exactly correctly. With the plugs out, look into the cylinder with a flashlight. The piston top will look black, but you're looking for a carbon buildup. Looking in isn't a comprehensive test, but it's cheap.
Check the old plugs for lean/rich. Chase down all the vacuum leaks - don't forget the two hoses running to the charcoal canister in the front right fender (remove the RF turn signal assembly to see in). Adjust the AMM to get the right mixture. Make sure the O2 sensor is working. Replace filters if you can't remember when they were last done.
After you've tuned it up, and set the timing to stock, see what octane rating you need. You very well may need higher octane fuel than the car is rated for. It's 16 years since it was made, and things change.
posted by 192.249....
, Fri, 27 Jun 2003 05:31:38 <-- Viewing This Message
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