High Engine Idle in QX4

[AlabamaDan]

Maybe y'all can tell me where to start. In my 1998 QX4 the engine idle seems a little high. Especially when first cranked. This morning I cranked it after it had been sitting inthe garage all night, probably 45 degrees or so and the engine started idling at 3500! After it warms up and stuff it's still idling around 1000. Seems to be running fine except for the idle. Any of you gurus out there have a place for me to start?

[AlabamaDan]

Come on guys. I've searched here and can't find the answer. Here's what I've done so far.

I cleaned the TB, probably not related but it didn't hurt anything and needed it. Cleaned the MAF with electrical cleaner. I also cleaned the connectors to the MAF and a few other places with the electrical cleaner. I replaced the battery with a new one since my old one was weak and needed replacing. I still have the same problem, actually it's worse.

When you crank it now it races to 4000 or 4500 rpm. It maintains a higher than usual idle when in drive or reverse, but it's really frustrating. Can someone please give me some more ideas on where to look.

Right now I have it sitting in the driveway with the battery unhooked to maybe reset the computer.

[qship96]

If the QX is similar to the Q45 method of idle control, I would think the Aux air control valve is misadjusted or broken- try setting HOT idle to 650-700RPM by turning the adjustment screw- as far as cold idle speed,does it use a similar design like the q45 where there is a hot wax contraption controlled by coolant temp flowing thru the throttlebody? If so, there may be a problem there causing the abnormally high COLD idlespeed- you must look in FSM to see both subsystems architecture and possible adjustment procedures.

EDIT.....first check for BINDING throttle cables, including the cruise control cable!!!!!

[AlabamaDan]

Uhg. I checked for the binding throttle cables and didn't see anything. I left the battery off overnight and no luck resetting the computer.

I'm not sure what you mean about the aux air control valve. Can you help explain more? I've been looking around in the FSM, but it doesn't seem to be the friendliest to me for troubleshooting. It's really good once you decide what you're going to replace, at least for me.

I drove it home and MPG was crappy on the interstate. It's also a little dangerous as you really have to push the brakes since it's idling at 1500-2000 RPM when you attempt to stop.

More help please?!?!?!?!

[qship96]

Q45 uses aux air control {AAC} valve to help control idle speed-check FSM to see what mechanism controls idle speed on the QX- probably similar setup. The AAC is basically a electric controlled air bypass with a mechanical screw you turn to adjust the amount of air allowed to pass thru, therefor changing idle speed.Look for idle speed adjustment section in the QX manual for details-should be in the engine control section.