Rough/erratic Idle

[cainer33]

So yeah, I have put some JJR's on and they fixed my misfire under boost, car runs great now.

But I have a rough idle, sometimes when I stop im doing 800rpm other times its 1100rpm.

I have cleaned out the AAC valve and the idle no longer hunts but I did notice something on my apexi turbo timer.

When the car was cold and I had it selected to O2, it was slowly counting down the voltage as the car warmed up, the idle reduced accordingly.

When I took it for a drive it stayed locked on 4.99volts, it didn't change at all even when I stopped.

So I am wondering, would an O2 sensor thats probably on its last legs and working intermittantly (which is what I think is happening) cause an idle that goes from normal range, but burbly, to 1100rpm and random times.

The idle isn't perfect either, bit of a burble here and there, up the rev range though, no problems at all.

[Muff]

could be.... have you got a votage stabiliser????

does your car idle better when it cold or hot?????

when the car is cold your o2 sensor is in what callled an open loop circut. therefore not really doing anything untill its warmed up, when it goes into a closed loop..... my sugestion is to put a voltmeter on it and test it out... or even take it out and have alook...... if it looks f*ked ... go and get another 1 from bosh......$75

GL

[lukebaldan]

Are you sure the O2 voltage is being reported correctly? Perhaps the turbo timer was not connected to the o2 sensor output? It should range from 0-1v (Sweeping back and worth when you hold revs constant above 1.5k)

A completely dead sensor (open circuit) will read ~0.3v (Reference voltage the car spits out).

It may spit out something close to constant 0 or 1v otherwise if something else is wrong with it.

If this was the case, your car will let you know. I have a 34 and if you unplug the o2 sensor, the check engine light comes on within 5-10 minutes.

In any case, the o2 sensor shouldn't cause problems at idle (I think the car runs in open loop anyways at idle).

Not sure about the 33's but the VCT solenoid can cause erratic idle if it's defective (What i have observed anyway by manually turning on/off the solenoid at idle with a consult cable).

Edited July 21, 2009 by lukebaldan