as the title says. when i'm sitting at a light the idle will be at around 900rpm and slowly goes up to around 1,200rpm and then drops to 700rpm engine shakes slightly and slowly goes back to 900rpm and repeats itself. this happens during normal operating temperature.

i'm running obd1 via obd2a-obd1 jumper harness ..a p06 vtec w/ phearable b16 basemap, walbro 255lph fuel pump, new oem fuel filter, iridium plugs and ngk plug wires.

what could be the problem.

 

vacum leak

 

yeah, i thought it would be a vaccum leak as well but the symptom happens very slowly...its not like a surging idle.

 

maybe the ECU is tuned to give you more fuel than you really need. Running rich can cause this problem.

Is your IACV and FITV hooked up properly?

Did you bleed the coolant? Check the coolant level in the reservior...if it's empty or past the low line, you might have air in your coolant. Bleed your coolant:

When the car is cold, take off the radiator cap. Fill the reserve tank to max. Turn on the car and let it run for a while until the radiator fan comes on one or two times. You might see bubbles coming up. Cap off the radiator, top off the reservior. Turn off the car....your idle should be back to normal after that if coolant air bubbles were your problem.

 

thanks for your reply. i believe the IACV is hooked up properly and i don't think this motor has a FITV, correct me if i'm wrong.

the reservior is low so i'll try the steps you suggested, hopefully it fixes the problem

 

i filledup the reserve tank and uncapped the rad cap and left engine running for 10 mins. stopped at a light and its still doing the same thing...any other suggestions guys?

 

clean the iacv