Drove for a couple of years with a progressively worse problem with pre-ignition on hills and running hot, '88 Integra with > 100k miles. During a routine maintenance I happened to have the upper timing belt cover off with the engine running, and noted a lot of belt vibration between the cam sprockets. This was a puzzle, since the belt and tensioner had been replaced about 20k earlier at the dealer. I went thru the factory procedure to adjust the belt and inspected every inch for problems - none. This completely stopped the vibration, my preignition and overheating vanished, and idle smoothed out completely. It stayed fine until the car was rear ended years later at 186k. Apparently belt tension was not adjusted correctly at the dealer.

Note I don't think the small valve timing oscillations were an issue - ignition timing was, since the distributor is cam-driven. Although this might have shown up if scoped, it did not with a timing light - the variations were cyclic and regular, so the pointer would remain steady when checked at a constant engine speed.

Moral may be to always do the work yourself, or check after others do, if you can.

Steve

 

wouldn't driving around with pre-ignition melt a hole right through the middle of the piston?

 

'Silent' preignition can, as can ignored heavy audible event. However, I simply adjusted my driving style to avoid the audible stuff... and was lucky too. Note that it was only under high load conditions I noted the problem, and timing variance was only probably a couple of degrees. Engine normally aspirated and stock, etc, no mods to aggravate the situation.

Steve

 

Sounds like you are getting some slight detonation, not pre-ignition..

 

what does pre-ignition sound/feel like?

 

pre-ignition sounds just like detonation.

 

Preignition (or detonation) cause a 'rattling' or 'pinging' sound that gets worse as load or heat increase. Modern lean-burn engines operate normally just shy of this condition, so it doesn't take much to push them over the edge - too low octane fuel, high combustion temperatures, vacuum leaks or malfunctioning EGR, etc. Some vehicles have 'knock' sensors that alter the ignition advance if it is detected.

Steve

 

hmm, Ive noticed that my car tends to tick more (louder) during idle after ive driven it hard (up to redline). I am going to do a valve adjustment, hopefully that will fix it. Would you say pre-detonation sounds like valve tapping?

 

Pre-ignition and detonation are two seperate things. And I don't know what the heck pre-detonation is.

But no, it doesn't sound like valve tap. It's much louder. like someone dropped a BB in your intake almost. It's not very likely that you are detonating at idle. Usually it only comes when pushing the car hard (lugging up hills, on the dyno without proper cooling, drag racing, etc..)

 

oops i meant pre-ignition