Question1. Idle is oscillating when not in gear, but seems to diminish when idling in gear.The oscillation appears to repeat every 5 seconds and a cycle is about 1 sec. on the rise and another sec. to drop. The idle is at 750 and would rise to about 850, and would go back down to 750. When in gear, the idle is about 650-700. Since i am focused on the ICV, I also observed that the voltage accross the ICV terminals when idling and at park, also oscillates with the RPM, and varies from about 4.35V to 4.70V. The oscillation is not much but I suspect this is not normal, and would like to understand the probable causes and correct the problem.
2. My other problem is rough idle, both when in gear, and otherwise. I observe that the rough idle is more so when not in gear. The engine does not die, although very noticeable, more so like a cylinder is missing. It runs smooth otherwise and tranny shifts smooth, so far as I can tell.
Steps that I have done are as follows:
1. Cleaned ICV and replaced both rubber connectors.
2. ICV measures about 5 OHMS. Closes fully when 12 volts in applied.
3. Voltage accross ICV terminals at idle and in park is 4.35 to 4.7V.
4. Coolant temp sensor(B11/2 - 4 terminals) measures about 370 OHMS for each pair of terminals measured diagonally. This was after engine was idling for a while. Resistance measurement when cold was very high.
5. Throttle valve switch(S29/2) - The Normally Closed terminal measured 0 OHMS, but would open with a slight movement of the throttle. The Normally Open terminal measured OPEN, and would close only at full throttle. ( ie it stays OPEN intil full throttle is reached.)
6. Pulled the plug wires one at a time at the distributor cap, in an effort to isolate the cause of rough idle, but suprisingly, did not observe any change in idle ( worse nor better...). I do not undertand this behavour at all. I was expecting to observe the idle to get worse, but to my ears, it was the same. Can someone expalin this to me?
7. Next Steps - The air distributor hoses and crossover breather hoses are hard as rock. These may still be the original parts. I am going to replace the hoses plus the injectors, and holders, etc..
I would appreciate your inputs. I am trying to undertand scenario#6 above, the rough idle and the idle oscillation.
AnswerYou sound like a mechanic. :SMILE:
This sounds like a vacuum leak where the computer is at the limit of compensation.
Check for any vacuum leaks, fix them first.
If this is a high miles vehicle, it is a good idea to replace the crossover breather hoses plus the injectors, and holders, etc..
Have a great day.
