• The site migration is complete! Hopefully everything transferred properly from the multiple decades old software we were using before. If you notice any issues please let me know, thanks! Also, I'm still working on things like chatbox, etc so hopefully those will be working in the next week or two.

knock & P0172



None of us start out good at diagnosing. Keep having issues and you'll get really good with it.

Uh.. Not sure. With the car/key off. Pull it and check it. Make sure the place where it goes is clean.
 
Ok I pulled the IAC valve off. Its grimy around the Oring. Ill clean it and the tb surface when it goes and see if anything changes.
 


Possibly another vacuum leake? Maybe somewhere near or before the the IAC sensor? I'll pull the MAF and TPS off and see if they are grimy like the IAC valve was. Or the sensor is failing?
 
Hold up there... let me explain how some of this stuff works before you do unnecessary work.

Vacuum leaks would cause the IAC to close. Because the IAC is nothing more than a computer controlled vacuum leak to control idle speed.

You are haviing a fuel dumping issue and we haven't really touched on that yet. I don't think the IAC is responsible for dumping fuel. You need to pull the plugs and tell us which cylinders are carboned if any look different than the rest.
 


Ok I checked the all. Only one was in prerfect condition, #2. The rest all had a black dot or burn on the insulator. Most appeared to have white stuff on the tip of the plug. So they are fouled? Or mechanicle damage? I looked up plugs on gnttype.org. It shows every kind of plug good or bad im thinking mine are lightly fouled.
 
So my spark plugs didnt look bad. No oil, barely any carbon deposit at all. Could I be running one heat range to high? Surely that cant be causing my high IAC numbers. Gnttype.org does mention lower intake manifold leaks.
 


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