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Idle Speed Adjustment

By Rob Microys

I would just like to update those who have idle speed adjusting woes. For a while since I had an idle speed adjustment problem just after I cleaned out my throttle body. I had to adjust the throttle screw all the way down. I had thought that I was adjusting the idle correctly with the TPS disconnected. But I had missed one important thing. I didn't stop the car before disconnecting the TPS. This is VERY important!

So for those of you who have their idle screws turned all the way down, I'm thinking that your engine idle speed was improperly set at some point in time. To properly set the idle speed, do the following:

As per my Nissan manual, it says something like:

  1. Warm up car properly... a short drive is best.
  2. Run engine at about 2000 rpm for about 2 minutes under no-load. Rev engine two or three times under no-load, then run engine at idle speed for about 1 minute.
  3. TURN OFF ENGINE, disconnect TPS, start engine.

    Personal comments. My car at this point would turn over and fire up but not run. I adjusted the screw upwards until I could start the engine such that it did not stall out.

  4. Rev engine 2-3000 rpms 2 or 3 times under no-load, then run engine at idle speed.
  5. Check base timing 15 +- 2 deg BTDC, adjust if required. (Mine was bang on 17 deg)
  6. Check idle speed, should be 750 +- 50 rpm. If no good continue on else go to 7. Rev engine 2 - 3000 rpm rpms 2 or 3 times under no-load, then run engine at idle speed. Adjust screw go to 6.
  7. Turn off engine, reconnect TPS, start engine.
  8. Rev engine 2-3000 rpms 2 or 3 times under no-load, then run engine at idle speed.
  9. Check idle speed, should be 800 +- 50 rpm. If at this point your idle isn't correct, there are some other components which should be checked which include (IACV-AAC valve, IACV-AAC harness and the ECM)

I know that others on the list have mentioned the fact that their cars have this symptom, and this might be the cure.