I have a 91' EF hatch. I just rebuild my stock D16 with rings and bearings and now i am getting a rough idol when the car is warm and been run for a while and it drops to a lower idol than normal. However, it isnt rough when idol isnt too low. But i am also getting an intermitant misfire. This is also only at idol that i feel a misfire.

Ive replaced the plugs, wires, and battery. I know my timing is somewhat correct because the car runs fine, but im not sure if its exactly correct. Also, im not sure how old my o2 sensor is and it was in the car when the old oil rings died. Could this problem be my o2 and timing? Or one and not the other? Or something else?

 

Since the misfire happens at idle I would start the car, pull the plug wires out from each cylinder for a few secs see which one you pull out and it stops misfiring. At that point you need to see if there is built up corrosion on the dizzy cap or maybe the wire or the plug itself that corresponds to that cylinder.

 

All those components are new within 6 months and the plugs and wires and new within 200 miles. The misfire is intermitant, so wouldnt a buildup or corrosion make a misfire more consistant? But ill start there and check them out.

 

Same issue happened on my prelude after I changed the timing belt. When the motor warms up, it idles rough and it misfires. Go to a local shop and have them do a leakdown compression test. On mine it turned out that there was a bent valve and that caused the problem. good luck

 

does it only do it at idle or whenever you step on the gas?

 

It only misfires at idol. I can feel it the most at cold idol when the idol is high. But during warm idol is when it drops low and runs rough. But it only drops low on certain occations, not all the time.