06Ron

My 2001 Bullit is exhibiting ever increasing spark knock at part throttle and is really hammering at WOT and this is on 92 Octane fuel. Has anyone else had this experience? It is obviously worse here in Phoenix in the summer but I can mitigate it with a can of octane improver but it is still there. Plugs have been changed with the exact same part. What temp is the stock thermostat supposed to be? Is there a knock sensor on these engines? Do you think it is carbon building up in combustion chamber? Would appreaciate any help or suggestions!

06Ron

Any Thoughts????

cliffyk

You might want to try a colder plug, but pull two or three of the new plugs and see what they look like--if a dead ash white I'd go down two heat ranges, otherwise just one. This would have the most effect if the spark knock is pre-ignition related.

Did you actually use the Motorcraft AWSF32PP, or some other plug?

It starts to open at 189-196°F, fully open at 212°. T-stats are rated by the higher end of their "starts to open" temperature, so it is a nominal "200°" unit. Switching to a lower rated thermostat will not make a lot of difference in combustion chamber temperatures, as related to pinging/spark knock. I run a 180°F unit here in Florida which is as low as you can go without altering the tune (FWIW I have changed my tune for the 180° t-stat).

No, only on the 4V engines.

That would be my first consideration. Do you know the car's history, was it "pampered/babied", short trips/long trips, what speeds? How many miles on the engine?

Do a compression check, if it is uncommonly high for the age/miles on the engine than carbon build-up could be the problem. Other than pulling the heads there is no real way to clean it out, although if you get the pinging/detonation under control a few hard pulls no and then, and long drives on the highway can--maybe-- blow some of it out.
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