For a while now, I've had a problem with spark knock in my car. I've tried everything from doing the seafoam thing(which helped for about a day), a complete tune-up which included fuel filter, pcv valve, and plugs, I also swapped the stock ac delco platinum plugs for ngk tr55 (which helped for about 2-3 days). Then someone told me that a lean condition can also cause "pinging". 3 weeks ago, I traded my k&n filter for a fram paper filter, and whadda ya know......no more spark knock. Can someone please explain this or give me some insight as to why a k&n filter will cause spark knock v. a paper filter?
The car has 135k on it.

 

I'll take a stab at this..

I think the knock may be doe to another factor... What mods do you have? When was the last time you changed the fuel filter? Do you have a tune?

I think you may not be getting the fuel you need.. Slightly restricting the intake air flow will slightly minimize the air in the overall mixture. K&N = more air, thus a lean mixture = detonation/knock, lean = hot, rich = cooler. Have you tried running Seafoam through the tank? Or another fuel injector cleaner?

This also may be due to carbon build up int he combustion chamber, slightly raising the compression ratio. If you have too much air and not the correct fuel ratio, that will cause detonation or knock.. It's also cause by premature ignition also from a hot engine.

 

My mods are in my signature (pretty much stock). Fuel filter was changed about 20-25k ago. As far as a tune goes, I don't know for sure. I do know that the guy who owned the car before me raced it. I did run seafoam in the tank about 20k ago, and Lucas fuel injector cleaner about 2k ago. Is there a recommended mileage to run an injector cleaner? From what you are saying, it sounds like I should do a really good tune-up, make sure all the fluids are good and take it to a shop to have it tuned. Someone once said that an engine should be tuned even if it has as much as a k&n filter. Is that true?

 

^ A Tune is always a good idea; 1: to make sure things are running at peak and 2: to make sure nothing is out of the ordinary. You can get a 'stock' mail order tune for around $175, IIRC..

You can run the injector cleaner every once in a while.. every 10k miles seems about right for me.. But that's just me.. Seafoam in the tank is always a good idea. I swear that stuff can cure cancer.

Anyway.. Yeah... Try a full tune up.. properly gapped plugs, Seafoam the **** out of it, down the throat and in the oil.. Check this thread if you have questions on the Seafoam. A good scan while driving would see any detonation, if it occurs on a certain cylinder, and it will capture the spark tables and what not. A dyno tune would be my recommendation AFTER the full tune up. PCV Valve too..

 

Check the fuel pressure too. A flakey fuel pump could cause lean conditions.

 

^It's funny you say that because I have another issue that's possibly fuel pump related. I guess I'll start there. I replaced a fuel pump on an old '86 Iroc I had a while back. Would my car be any different?

 

^Not very different at all.