Symptoms:
Progression:
Clues:
Current Guesses:
Heat is causing a sensor to act up, but which one? The problem appears related to heat. Whether that is coolant temp heat or engine bay heat I do not know. The coolant did not run hot while at the track, but of course the engine bay was significantly warmer than normal.
I'm honestly not sure how to trouble shoot what remains. I might take the car to a different mechanic and have it smoke tested again, but that's bordering on just "throwing money" at the problem. Plus, nothing in my current knowledge can explain why the idle can be so erratic and then boom, it's fine after sitting there for a bit.
Does anyone have any ideas? I believe I've run through all the basic trouble shooting and am at a loss.
- Idle fluctuates between 500 and 1100 rpm.
- Only fluctuates when warm.
- Idle suddenly becomes solid after 10-30 seconds. The "solid" warm state is the same 700rpm that it nails when the engine is cold.
- When in this fluctuation state, it will hesitate to come off idle.
Progression:
- This used to only happen at stoplights, and only one in 5-10 of them.
- The most noticeable change was during Friday's track day, where the idle would not settle down over the course of 60 seconds, and varied a lot more, maybe 400-1200 rpm and seemingly threatened to die on me.
- I took it back out again today and the original symptoms popped up, fading again after 15 seconds or so.
Clues:
- On the way too the track via freeway, I got a 1221 (O2 sensor) code that wouldn't go away (usually clears in a few seconds). While at the track the code remained (not unusual), and then vanished on the way home. I have not received the code since, nor was it common before the day I went to the track.
- Suspecting the intermittent idle problem was vacuum related, I had a smoke test done. Car turned up a clean bill of health with no leaks, though I was not present to verify the procedure.
- The TPS sensor checks out.
- The CTS shows 2950 ohm at 61f, and 255 ohms at 195f. This appears within spec.
- O2 sensor is only a couple years old.
- ICV currently buzzes, and was cleaned and proven to work 6 months ago.
- Car runs good and smooth. While I could be missing 10hp I suppose, I'm confident I'm not missing 50.
Current Guesses:
Heat is causing a sensor to act up, but which one? The problem appears related to heat. Whether that is coolant temp heat or engine bay heat I do not know. The coolant did not run hot while at the track, but of course the engine bay was significantly warmer than normal.
I'm honestly not sure how to trouble shoot what remains. I might take the car to a different mechanic and have it smoke tested again, but that's bordering on just "throwing money" at the problem. Plus, nothing in my current knowledge can explain why the idle can be so erratic and then boom, it's fine after sitting there for a bit.
Does anyone have any ideas? I believe I've run through all the basic trouble shooting and am at a loss.
Comment