My JDM ITR motor has a weird idle. it idles and sounds like its a v8 with cams. Sprayed down all the vacuum lines and gasket areas and no leak. Im getting no check engine lights. I cleaned out the IACV. Compression test numbers are perfect. I adjusted the idle screw and no difference. Performance wise there are no problems, the idle will get low and the ecu will catch it and raise it,repeating the process over and over, the whole time it will not idle over 1000 rpms. Im stumped

 

Check your air filter?

 

regap your spark plugs. that may help

 

im going to replace the plugs with stock NGKs. My JDM ITR engine came stock with a 7 heat range, will it matter if i switch to a 6 range