Spark knocking causes and what can be done to fix it?

patsbowen

My 1995 Toyota Camry has been spark knocking for a while. I took it in to the toyota dealer, and they adjusted the timing, cleaned the injectors, cleaned the carbon. Now they say it may be the timing belt needs adjusting. Several people said they felt it was not the belt. Do you have any suggestions or have any answers as to what else the cause could be. I don't have money to dig in my pockets for nothing. Thanks...Pat

alcan

The spark knock or ping is 2 flame fronts colliding in the combustion chamber, the shock wave of which can eventually blow holes through the piston crowns if severe enough. In late model engines the causes can include:
- fuel octane too low
- EGR system malfunction
- knock sensor (if equipped) malfunction
- PCM software not retarding ignition timing as required
- high engine operating temperature
- lean fuel mixture
- carbon deposits on piston crowns/combustion chambers

armtdm

First put in two bottles of the Chevron Techron injector cleaner and try a full tank of 92 octane gas. If the higher octane stops the problem you either have a timing issue or carbon build up The cheap fix is to continue with the premium gas rather then the other options. Unless ofcourse, it is time for a new timing belt, doubt that this is the cause though

alcan

You're right on the last count, armtdm. The only way a timing belt could contribute to spark knock is if belt slippage allowed the camshaft(s) to jump AHEAD a tooth, possibly from engine run-on at shutdown. This would advance the distributor or misposition the cam position sensor reluctor ring. It occurs very infrequently, and usually causes major engine performance and drivability concerns such as hard starting, poor idle, lack of power, overheating, etc. I would respectfully suggest that timing belt replacement solely for the purpose of correcting a spark ping is a fishing trip on the part of the dealer tech's.

Mr_Shiftright

I think any shop that is trying to fix spark knock with a new timing belt is a shop that is desperately looking for an answer to a problem it does not understand very well. That is like saying every headache is a brain tumor.

Cheapest fix might be higher octane fuel. If that doesn't work, the most likely culprit is engine timing and the devices that regulate it. Seems to me that an engine running hot enough to detonate would be fairly obvious.