Renix, low idle.

I've got a low idle on my 1989 4.0 AW4 Comanche. It's idling at the first line on the Tachometer, sometimes slightly below. I was told to tighten the intake manifold bolts (Did that) and to check the voltage at the TPS. I tested across A and B and get 4.14 volts on the square connector. If I ground the multimeter to the block, and place the positive in terminal A, I get 5.55V. Does that sound right?

make sure the throttlebody is clean. there is a set screw for the idle stop that you can adjust, but you will have to reset the TPS afterward. (not much). also there is a aluminum plug on the side of the throttlebody you can pry out with a pick and back out the torx screw until the idle comes up a bit. then seal that back off with some rtv so the screw wont back out on its own.

I'd start by cleaning the throttle body and while you're at it, clean the idle air control. Both get carboned up.

The IAC and Throttle body were cleaned, and the IAC passageway looks to be clear.

So I want to back out the Torx screw on the throttle body? How do I adjust the throttle stop? All that is visible are a few threads with some loc-tight on them.

If everything is clean then you can mess with the throttle stop screw. Normally, you shouldn't need to touch it. I had to after changing the throttle arm (needed one with the knob for the tranny cable). Its a small set screw that takes a small allen wrench. The head is hiding up in there. Turn it maybe 1/8 turn at a time.

I would leave the throttle stop screw alone, it is set like it is for a reason. If you need to adjust idle, use the rpm trim adjustment, which is the one hidden in the round casting on the side of the throttle body with a plug over it, as mentioned above. But before you do anything, finish your TPS adjustment, and since idle control is basically a controlled vacuum leak around the throttle plate, has anything changed that uses vacuum, like the PCV system?? Is it plugged up?

Your testing proceedure doesn't sound quite right. Shouldn't it be A-D for input voltage, and B-D for output?? I'm no expert on this, so I recommend you find the Renix Manual online and print a copy. It's been a while but I think I got mine off pirate4x4 in the tech section. It covers all adjustments mentioned!

duplicate post, sorry!

lawsoncl said:

If everything is clean then you can mess with the throttle stop screw. Normally, you shouldn't need to touch it. I had to after changing the throttle arm (needed one with the knob for the tranny cable). Its a small set screw that takes a small allen wrench. The head is hiding up in there. Turn it maybe 1/8 turn at a time.

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you can turn the set screw a little at a time. it will be fine, what i stated above is how we were trained to adjust the base idle and tps in A.M.C training 20 years ago