Idle Problem - Too Low - 1990 RRC

[Irons1990County]

I've recently started having a problem with our 1990 RRC running a very low idle such that it will stall when sitting at a light in Drive. It will idle very low and stay running in Park or Neutral. Here's what I've tried so far:

1. Cleaned the air idle control valve. Seemed to help a little, but perhaps it should be replaced?

2. Replaced the fueld filter. Non-stock and undersized and of unknown vintage. Seemed to help a little.

3. Replaced the air filter. Non-stock and smaller and of unkown vintage. No noticable change.

Any suggestions for next steps? Replace the air idle control valve? Adjust the base idle? Thanks.

[GDEclassic]

I believe the idle is controlled electronically. not sure. but i wud check the timing, cap and rotor, plugs and wires obviously, and def make sure all your vacuum hoses are connected and not blocked with a bunch of carbon and shit inside. especially the T-junction. ANd def. the idle air control valve cud need replacing, i think i might have to do mine too. I believe someone told me one from a chevy astro van will work, check out rangerovers.net to research that, cuz i think the golden green valve is atleast a couple hundred bucks.

[roverturbo]

check the stepper motor, could need cleaning, so could ur MAF meter, theres a special spray u can get for it..
is it over heating at all? water ways may be blocked
spark plugs, leeds, timing of course

cheers

[lsawicki]

Yes, I would check to make sure you have no leaks in any of the vacuum hoses, which induces extra air into the engine, causing RPM's to fall. A good way to check for leaks in the hoses is to (carefully) spray carb cleaner on the hoses and listen for a change in tone.

As far as idle control, it can be adjusted manually. I actually did this successfully yesterday. I have the shop manual and it says you have to get blanking hoses and whatnot for the idle air bypass hose, but this also works:

1.) On the top of the throttle body you will see a hole (possibly covered by an anti tamper plug) for the base idle adjuster. This is a metal plug that needs to be partially drilled with a self-tapping metal screw, which then can be popped off. This is so LR dealers can get more business...

2.) Remove the air bypass hose from the throttle body, which will cause the engine to speed up to 2500rpm or so. Unplug the connector to the idle motor after 5 seconds then reconnect the hose.

3.)Squeeze the hose shut with needle nose vise grips and adjust the base idle using an allen wrench to give an idle speed of 6-700rpm. Get the lowest speed you can that gives smooth running and does not stall when blipping the throttle. Screw clockwise for slower idle, counterclockwise for faster idle.

4.) Reconnect the idle stepper and remove the vise grip and you should be done.

[Irons1990County]

Thanks for the help Isawicki. I will try your suggestion today. I've already installed a new stepper motor and that did not help.

I called Atlantic British last week and was told that the low idle could not be due to vacuum lines because a vacuum leak would cause the idle to rise.

[yieldsign2]

Originally Posted by Irons1990County

I called Atlantic British last week and was told that the low idle could not be due to vacuum lines because a vacuum leak would cause the idle to rise.

I tend to doubt that is always true....

[Irons1990County]

Isawicki, I tried your suggestions and here's what happened:

1. Started the truck and removed the air bypass hose from the throttle body and the engine died after a few seconds.
2. Restarted the truck and operated the throttle by hand to keep the engine running while removing the air bypass hose.
3. Unplugged the connector to the idle motor after five seconds and reconnected the air bypass hose.
4. Clamped the air bypass hose and used a hex wrench to adjust the idle up to 600 rpm. At this point the engine seemed to be be running very smoothly even kicking up and then releasing the throttle by hand.
5. Reconnected the idle motor, unclamped the hose and the idle returned to about 370 rpm.
6. There is now a distinct and loud harmonic whistle at idle (emanating from the opening of the air intake) which I can only imagine relates in some way to the change made to the idle adjustment.

I am becoming convinced that there is some kind of serious vacuum issue. I also wonder if the new idle motor I bought is defective or if I should try running without it connected. Any ideas?