I have a 2.7 liter 4 banger with TBI injection.
This summer I’ve been having a problem with Spark knock that I haven’t had previously.
I’ve pulled the spark plugs and found 1 plug which looks pretty obvious like it has seen some detonation, while the other 3 plugs look fine.
I changed all 4 plugs and went to plugs cooler on the heat range, but it did not help.
I’ve checked the cranking compression. 2 cylinders at 170 (1 of which was the cylinder with the bad plug), the other 2 are at 150 and 160.
I’ve tried 93 Octane gas from two different stations. Even added Royal Purple octane booster which should raise the Octane by 3 FULL points. But it had no effect.
I’ve run Berryman’s cleaner thru the vacuum port. No effect
Currently running Berrymans cleaner in the gas tank. No effect yet, but tank is still pretty full.
I have a programmable ECU and I’ve lowered the timing about 20% in the area where I hear the knock. (Moderate to Full Throttle) at 1800 to 2300 RPM. This helped a little, but still have the problem.
I’ve checked the valve lash and all seem OK.
Fuel pressure is good. Wide Band O2 sensor shows correct AFR.
Other than pulling off the Cylinder Head, is there anything else I can do to get handle on this spark knock problem?
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