Here's, my the deal. I own a 1990 honda civic lx sedan. The problem all started when I got my car back from the local muffler shop after I got my 2.5" exhaust put on. I was driving it home and I pulled up to a stop light and it started to idle high, then low, high, then low. Idle was ranging from about 1500 rpm's to 2500 rpm's

I did some diagnosing and right away I thought I found my problem. I unplugged the MAP sensor and the car idled perfect! So I assumed the problem was a bad MAP sensor. WRONG! As soon as the engine got up to normal operating it started the loopy idle again. So $100.00+ and a new map sensor later, still has the loopy idle. Anyone have any clue what it might be??

 

check engine light come on? if so check code, otherwise looks like other similar issues have been o2 sensors, air leak somewhere, or i was originally going to say throttle position sensor is the first thing that came to mind

 

http://www.superhonda.com/forum/f55/...oblems-259965/ this may help also i found

 

If the car idles fine without the map sensor clip plugged in it is most likely a vacuum leak, check all of your lines & make sure nothing re-arranged. IF not.. adjust your IACV screw & throw in some intake-medic. Could also be your TPS. GL.

 

Reset the ecu...sounds crazy but it worked for me a while back.

I swapped in a sohc zc, would rev it to about 2000rpm then it would start fluctuating, no matter what i did it just stayed that way. Then i reset the ecu, and it fixed itself.

Air is escaping the combustion chamber faster than before, so anything related to the air:fuel needs to have an ecu reset.