2001 Maxima GLE, 153,000 miles. IACV has been replaced a few years ago. The famous IACV bypass performed at same time.

Just started having idle issues. Engine fully warm. Wants to pretty much idle normally within spec, but sometimes, when at a stop light (and still in Drive) I can feel her drop 100-200 rpms (you can feel the "shudder"). Engine has not stalled at any time yet.

Tonight, I put her in park and blipped the gas pedal. Idle will drop all the way down to 400rpm, and then return to normal. It's not really "hunting" and doesn't "hunt" for idle high above the stock/normal 650RPM +/-50. If you want to call it "hunting" it is only on the lower side of stock.

I'm guessing I need to check for vacuum leaks? Cat converter finally going? PCV valve failing (was replaced a few years ago)? Failing O2 sensor?

Note: Had issue with alternator and brake light coming on a couple months ago, but has not returned after cleaning positive battery terminal. No other issues known.

 

I would check and make sure your not losing coolant. air in the cooling system will throw the air fuel ratio off. I had it so bad one time in my CRX the car would stall and had a hard time starting back up. ended up changing all the clamps, radiator cap and bleed the system, problem solved.

 

I'm not an expert mechanic. However, cooling systems are completely separate from the intake system that controls the air-fuel mixture for combustion.

 

mostly right. fuel controls on a crx are extremely primitive and heavily influenced by ECT readings. not so much on these cars. coolant temp is a factor in AFR but it has much less of an effect on engine performance.

i would clean the TB and IAC.

 

No codes are being thrown?

 

I'd start by cleaning engine grounds.