i was running HKS Hi-Power, FIPK/cooling plate, MR resonated test pipe for about a month with no CEL or anything. after i installed my Mugen header, i got a CEL for knock sensor malfunction. i cleared the code and it stayed off in my normal driving, but as soon as i opened it up it came on. this happened consistently--the CEL would stay off after i cleared it, until i started revving it high. it's also weird that once the CEL came on, the engine would stutter/vibrate a lot/idle very low when i'm off the gas at a stop, but once i cleared the code this would stop. but then once the code came on it would start to happen again. it's weird because i thought that the mechanical problem would cause the code to be thrown, not the code causing the mechanical problem...

my uncle told me that because i freed up the airflow in to and out of the engine, the ECU isn't used to the extra flow, so it's having a hard time compensating. (he said something to that effect). i was wondering if this would stop once i get my VAFCII tuned...

any help would be appreciated!

 

Try disconnecting the battery for about 10 min. than reconnect and start the engine and let it idel for a couple of mins. Thie might help the computer re-learn. Don't know if it will help, I know it can't hurt. Good Luck.

 

^^i thought clearing the code would do the same thing, but i'll try this now and post what happened later tonight.

thanks

 

ok...

problem 100% fixed!

thanks JimmyB. it was pretty obvious, so i don't know why i didn't do it earlier. i thought clearing the code would have the same effect. haha stupid me.


thanks again

 

That may not have fixed it. It just cleared the ECU and the ECU will have to relearn. But if you are running lean, the car will knock. If that is the case, and your sensor is bad, the CEL will return. Keep an eye on it.

 

yes, it came back the next time i drove the car

will getting my VAFCII tuned fix this??

 

I doubt it. I bet you need to replace the sensor. They retail for 150 and they are a PIA to change. Hard to reach.

 

it must be somewhere underneath the valve cover--am i right? something tells me the CEL is not because the sensor is actually bad, the ECU might just not be adjusting to the mods correctly. because i just got the code once i installed the header. literally within 30 seconds after starting the engine.

 

Chances are, that since it happend right after you were under the hood, that you pulled or loosened the cable. Definately check the harness. Also give the area you worked in a good look over for loose vacuum lines and stuff.

 

the things i circled in green are the things i played around with while installing the header. i also broke a stud and had to replace it. could any of those circled things, or pulling out a stud have affected the knock sensor?


excuse my dirty engine bay