Rep Power: 0

Hey all! Having a bit of issue with my 7th gen Honda with 156k. Purchased this July with 153k. Replaced spark plugs, coils, engine mounts and cleaned throttle body and IAC valve last month due to an idling issue that started. The car is experiencing low idle at around 500rpms or less sometimes as it’s inconsistent. All fine until it warms to proper operating temps then the idle drops and the car starts vibrating from the front, but only sometimes at that idle speed. It gets worse and idle drops lower if you turn on the AC. Its not the engine mounts as those are new, plugs/coils are NGK and Denso or what came on the car. According to the Carfax the timing belt was replaced in 2012 but idk what the mileage was. When I rev the car it levels at 1000rpm for a sec but then drops below 500 to almost dying, then back up to around 500rpm. Could timing be off? What else could be causing an idle issue, if it is one? Mechanic told me it sounded like a vibration inside the engine but it’s not present all the time. A misfire? When changing the plugs I did find oil around the 4th cylinder plug and all 4 had some scorched looking porcelain, idk when those were last changed. Any ideas? I don’t want anything bad to happen

 
Rep Power: 118

Unplug the O2 sensor so the engine is forced to stay in open loop mode and then see if the engine acts normal when fully warmed up.

You will instantly confirm if it’s a heat issue or engine control issue.

 
Rep Power: 0

The one plugged into the intake manifold right? Do I unplug before/after I start the car?

 
Rep Power: 222

No the one in the exhaust manifold, and before you start the car