02 lancer weird rough idle
 

its an 2002 lancer with a 2.0 automatic with just under 300,000 miles. the problem just started a couple days ago. i live in a cold area like when i start it in the morning its 15 degrees outside. ok so when i start it it starts and revs down to 800rpms for ten to twenty seconds then it spikes to 2000rpms and the fast idle works fine after that. once it warms up and revs down back to 800 it random misses. no engine light havent hooked a scanner to see if there is pending codes. if its in gear it quits missing if its in park or neutral it starts missing. if its in gear it doesnt miss at all. The weird fast idle and the idle miss happend around the same time so thinking both are linked to the same problem. i put new wires on about two years ago and plugs but i just changed plugs 4 months ago. put in ngk plugs not the cheap ones. could it be bad gas but i wouldnt think it would mess up the fast idle. any advice would be greatly appreciated thank you. any questions just ask.

kinda figured it out started missing real bad today so i took of the coil to check the plugs and saw the boot was torn to ****. so i went and bought one put it on and it quit missing. every once in awhile it would miss for a sec. i just thought it was still burning the gas off in the cylinder. two min later i was idling at a red light and pop something in the top end gave out sounds like a bent valve or something. haven't pulled it apart yet to verify but hey 300,000 miles on original tranny and engine. kinda pissed me off though it didnt break at 5000 rpms just at 900 like wtf and i just bought that rubber boot 15.89 and a full tank of premium gas.

Idle air control valve problem. It's just carbon build up. Use throttle cleaner and clean it out. Check out an article i wrote, how to clean it out. Subscribe if you like my blog.

http://www.enginemisfire.com/10-step...-control-valve