Another High Idle Thread (slightly different than the rest)
 

99 Isuzu Rodeo. 4wd. 3.2L.

Once or twice a week, I get an annoying high idle immediately after start up. I start the car, and the RPM's slowly start to climb, sometimes up to 2.5 or 3k. If I let the car idle for 10 or 15 minutes or so, the RPM's will slowly go down to where they should be.

When I let it idle, the RPM's go down in a step like fashion. Every minute or so, the gauge decreases by a small increment. In addition, It only seems to have this high idle problem during moist and cool weather conditions. This has been going on since I bought the car three years ago.

At first, I thought it was the leaking intake manifold gasket issue that the 98 and 99's have. So I replaced the gasket, and cleaned the throttle body while I had things torn apart. No luck.

In addition, it threw the egr code a couple weeks ago. I took the egr off and cleaned it out with carb cleaner. I haven't had a check engine light since, but still have the high idle issue.


Any ideas? Could a bad O2 sensor cause this?

Im new to this forum and have posted an issue with Stalling after warmup so maybe you can help me too.
I also had this issue with High idle both cold and sometimes after driving a while when coming to a stop light. Eventually I got a check engine light.
I ran 2 large bottles (4 fillups, 1/2 bottle each) of the Lucas fuel system cleaner (Clear bottle), and this went away. It could also be a dirty or fault Idle air control valve, which I have since replaced as well.
good luck.

outtamyway,

The idle air control valve is a good idea. If I get a chance, I will try cleaning it tomorrow. I run seafoam through my fuel system every few months, so I don't think its a problem in my fuel system.

When yours was idling high, did it make a sucking noise that you could hear from inside the cab?

The sucking noise almost sounds like there is air leaking, but I have ruled that out. Maybe, since the engine is idling high, it is trying to take in more air than the throttle body is allowing? Maybe the sucking noise is caused by restricted air flow at the butterfly? Not sure, just thinking off the top of my head......

i would check that O2 sensor...that seems to be the culprit.

Thanks, I will check/replace that as well.

I just checked RockAuto, is there a total of 4 O2 sensors, or am I interpreting it wrong?

Edit: I did some more reading, yeah there is 4 O2 sensors. Two on each bank.

I did not hear any sucking noises that I can remember,
I checked on the O2 sensors also and yes there are indeed 4 of them.
All are seen from below 2 near the front of the exhaust and 2 behind near the Cat. conv.
I too am not sure whch to replace first. Perhaps all?

I think im going to replace all of them. Im at 112K, so its probably time to replace them anyway.

RockAuto has Denso brand O2 sensors for $30.79 per pair. Sounds like a decent deal. Part # 2344012

Today I took out the idle air control valve and cleaned it. Member boritz at planetisuzu had some useful info. It seems to be running better so far. I will have to wait and see if it does it again.

The thread is located here:

http://forum.planetisuzoo.com/viewto...=321906#321906

I totally forgot about the IAC valve... good thing someone told you that before you spent a bunch of money on o2 sensors!

Im glad your problem is solved dan5505.

the o2 sensors before the cat's are for the fuel, it measures how much unburned fuel is coming out and then the ones after the cat measure how much the cat filters or burns off. so if i was to replace any, it wud be the ones before the catalytic coverter.