Idling Problems with 89 Dakota

I have run out of ideas and need help.

'89 Dakota 4x4
3.9L TBI
AT
120,200

Since about April 4 I have had problems with the idle in my truck. Every time I come to a stop or slow down (below the regular idle speed for that gear) it idles at about 100RPM, or it dies. Sometimes if I wait long enough the idle will recover back to normal. From June until mid-August I never had any problems, it was fine. Ever since then the problems have been ongoing.

I have replaced:
ISCA
TPS
Ignition Coil, Spark Plugs, Wires, Distributor Cap, Rotor.
Water Pump
Belts
Computer

I have checked the timing chain, and the timing itself.

I have 3 possible problems and would like input: 1) Air pump, 2)O2 Sensor, 3)Vacuum/air leaks.

Any ideas?

I replaced the computer yesterday to no avail. It still idles wrong, but runs better overall.

Why didn't you replace the idle air control valve yet? I bet you that's all that is wrong here, and it sounds like you've spent hundreds of dollars already...

My truck doens't have one.

You said EFI. It must have one.

Maybe you mean TBI?

Yeah, that's it.

Sorry i've been out of it a little bit.

So which one is it? Get it figured out yet or what?

It's TBI.

Sorry about that.

I don't think you should worry about your O2 sensor. I have the same prob with my 88 D100 w/ rebuilt 3.9 So far I've replaced the TB (used), computer, O2 sensor, Vehicle Speed Sensor in tranny, as well as what youve put on. Anybody have any ideas?

I had the exact same problem with my 94 Dakota with about the same miles. It was a crack in a vacuum canister. The dealership fixed it so I don't know exactly what part it was.

If there is any way you could find out, would you? You have no idea what it would mean to me.

UPDATE: I checked my tranny fluid and added a full Quart to it and I didn't have any problems for a while but now I am low on fluid again and I am having the same problems. But I have no other ideas.

The only thing my receipt shows is the following:
FP Number: 55035902
Description: Resevoir 14067001
Price: $7.50

Hope this helps!

I'll see what I can dig up.

Thanks!!

I had the same problem after installing a new egr valve. When i stoped at stop signs the rpm's droped dangerously low. to the point of power loss to everything, steering brakes, all of it. I took it to a dealer to have a diagnostic and talk with " an expert". know one could help. So I put the old egr valve back in and solved my problem. The new egr valve was defective and proved to be the problem.

Thanks. My main problem was the front pump in my transmission was fried, and spun a bushing. So my tranny was pretty worthless. After I got that back in I changed my EGR valve, and now it runs like new.

Thanks everyone for all of your help and ideas.