I recently went to take my 89 out for a drive after it was sitting for a few months. Upon starting it, it began running rough ( never had this issue ever before). I rev'ed the engine a bit and it cleared up. Fast forward a few days now and upon start up it struggles to keep running. It will start but it sounds and smells like it is flooding, I can rev. the engine a bit and it will miss, buck and smoke will come out the tail pipe, not blue smoke just very fuel rich smoke. sometimes it will start to run good after a few minutes but as soon as a give it a rev the rpms will just tank out and die. I feel like it is starving for air I can remove one of the vacuum lines running to the manifold and it will run just a little bit better but not much. I am kind of leaning to a faulty idle air control valve. I feel like its not opening up on start up and idle. The situation has progressively gotten worse so much so it will not even really run. I know other cars are programmed to run open loop (meaning that it will just fire the injectors, without looking at the sensor feedback) until it warms up then switch to closed loop and use the sensor feed back to regulate the air fuel ratio. Knowing this information and knowing that its happening both cold and hot running conditions is pointing to the Idle air valve. Any input before I go and but a new valve would be great. Thank you!!!

is there a code? could also be the 02 sensor.

sounds pretty darn close to what I am experiencing. I will be following closely <img src="/forums/images/graemlins/wink.gif" alt="" /> Wish I could help but I am new to the montero and not a very experienced Wrencher...

Per haztoys. "Wiring tune-up"

I had the same problem ended up being the fuel pump was bad, and not putting out enough PSI. Check your fuel pressure. fasteddy has a good post on how to do this.

So yesterday I had some time and replaced the idle air with one I had on the self of questionable condition. It died automatically. I cleaned the old one and re installed it. it ran about the same. I ran the engine without the intake manifold hose on and surprisingly ran ok. weird. so this got me thinking about the mass air. I don't know how or when it plays into regulating the air fuel mixture but I unplugged it while the engine was running and it had a direct impact on a sudden increase in how the engine was running. (keep in mind that there is no air passing though it). I reinstalled the intake manifold hose and plugged the mass air flow sensor in and fired it back up. Back to running rough. I pulled the connector for the mass air and it cleared up. It was clearing running rich but running far smoother then normal. I hope to replace the mass air flow sensor with a spare I have on the shelf and see what happens. It is the original unit so its 25 years old. Do these units go bad, what is the failure mode and can I repair it. It looks pretty simple? Any input would be greatly appreciated. Its kind of suspicious now because the reason I hadn't been driving it for a while was because it was getting terrible gas millage compared to what I remembered. But after not driving it for a few months I didn't know if I just forgot how bad it was or if I was just loosing my marbles. <img src="/forums/images/graemlins/confused.gif" alt="" />

I managed to find some time last night to swap out the mass air flow sensor on the raider with a spare unit I had. I plugged it in and fired it up and poof* ** back to running like a champ. No check engine light, no trouble codes. But I am just happy it turned out to be something simple. Has anybody ever rebuild one of theses units? There really doesn't seem to be that much to it. I hope this helps anybody else. I am interested to see if my gas mileage goes back to normal now.

I had the idle air bypass vavle go bad in my TB (the water controlled one , not the the electric ICS).
Ran me ragged cause I didn't know about they part and it's not in the FSM. Folks here on The WIRE set me straight.
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I looked into Mass Air as that seemed to be the problem with my unsolvable fast idle.
2 test on mass air (other than cracked wires at the terminal)
The little resister looking thing(visable) can do a ohm test.
The rest of the gizmo is the honeycomb air vortex control(it can get bent or gunked which make air swerl wrong. Air flow /dencity is measure with sound ways in the properly flowing air.
This part according to AllDataPro can be tested with an ocilloscope.
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((On my TB I ended up cutting gasket material to block 1 of 2 air ports thru the bottom of the TB and did away with water hoses.))