Hello everyone, I'm trying to figure out an idle issue that my car is having and was hoping I can get some insight. So, I just recently installed a brand new 20g on my evo along with upper and lower IC piping, BOV, an intake, EBC, and a test pipe. Before installing all those parts my car ran perfectly fine, but now my car has an idle issue when it's warmed up. I did have a code for a small EVAP leak but my car idled fine even with that code. Idle is completely fine during the cold start up, but when the engine gets up to temp my idle starts dropping about 100-200 rpms for a while, spikes, then stabilizes back to 850rpm. Car accelerates completely fine and no misfires while driving. I had a buddy do a boost leak test and there were none. He also hooked up his smoke machine and did not see any leaks anywhere. Checked my plugs today and they're completely fine and gapped correctly. Going to check again tomorrow for vacuum leaks to make sure my buddy didn't miss a small one. Also, going to try another MAF sensor that i have laying around to see if it's a MAF issue. I'm hoping to fix this issue so I can get my car tuned.

 

did you connect the pcv hose to the intake?

 

I’m pretty sure I did lol. But I’m going to double check all the vacuum lines just in case I missed something.

 

Here are some thoughts that come to mind for things that I would try:

• Made big intake changes, adding volume and reducing restrictions. Reset your fuel trims by pulling the negative battery cable for a few seconds.
• Using a logger like evoscan, see whether your car is having difficulty maintaining the target idle rpm when warm. If it is having difficulty, look at the IACV steps value. Maybe IACV issue.
• Do the base idle set screw (BISS) reset procedure to reset your idle rpm and idle set screw position for your new piping. I don't think just changing piping and valves should cause the idle set screw to need resetting but these cars are pretty old now... usually lot of owners, probably lots of mods. No telling what was messed with, good to confirm a proper setting.

 

Link to Evo Scan?

Thank you

 

evoscan