As posted in a different thread, I have an intermittant high idle prob. Thought I had fixed it, but its back. So far I have cleaned the Mass Air Flow (MAF) sensor and yes I used sensor safe cleaner, replaced the Idle Air Control valve (IAC), and Throttle Position Sensor (TPS), cleaned the throttlebody, checked for intake manifold gasket leaks via spraying around the manifold with carb cleaner.
I cannot rule out other vacuum leaks as I dont really know where to look or a easy method of locating them, but nothing really stands out as far as cracked or missing hoses.
The PCM never throws codes, CEL light never turns on despite idle that somtimes reaches 2600RPM! Somtimes it idles ok tho, but usually around 1000-1200. PCM appears working because my OBDII reader sends live real-time data to my Droid phone just fine. (can the PCM just partially fail?)
Here is what I have left IMHO:
Some here have suggested fuel pressure regulator. I don't know how to test this. Other forums have reported possible fuel pump itself.
Some vacuum leak SOMEWHERE, again, how to test?
One forum found a fix on a 3.5L trooper in that the power steering pump pressure sensor may be failing. On that forum the diagnoses was apparently correct. Apparently the logic goes that when that sensor gives a low reading, the PCM bumps up the idle to increase pressure in the lines. I find this interesting as the last time my oil was changed, the ppl there showed me some leakage they identified as power steering fluid. It was apparently a slow leak as it never drips on the driveway, but it was leaking around or onto the "intercooler" where it enters the radiator (lower left side of the radiator as you face the front of the VX). They showed me the evidence of the leak, it was definitely red fluid. They were not concerned as the leak was apparently small.
So... any pro-tips? I really, really do not want to go to an average joe mechanic only to have him replace all the stuff I already replaced (which to me are the obvious and easy things). Only to have to have it back the next week for the same problem. At that rate this could take months and hundreds of dollars of labor costs before its fixed.
Any thoughts appreciated.
Oh and for you ppl with Scangauge or other realtime OBD interfaces, where can I find proper baseline numbers for what I *should* be reading from data such as MAF and intake pressure?
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