90 Mighty Max 2.4l strange idle problem

Ok guys this is my first post on this forum so be kind...

I recently bought my 1990 2.4L and have noticed a couple of strange problems. I'm new to Mitsubishi engines in general and this old (I've had imports but Honda's, 94 Integra, and 99 Civic). I'm familiar with injection systems and squeezing every bit of HP out of these rides with tuning, exhaust, intake ect.., but the system on this Mighty Max is kinda weird to me. The MAF is a box in the cleaner, and the IAC valve is like nothing i've seen. To make matters worse the IAC costs like $300 for a replacement! Anyway, my problems...

I had some trouble with it bucking at low RPMs so I did the Sea Foam clean and complete ignition tune up (changed Dis. cap, rotor button, wires and plugs) and it rarely does that any more.

The truck fires right up, on the first or second crank, sweet, but sometimes it will idle low then rev up, then go back down so low I have to keep my foot in the gas to keep it running. It did this so consistently (for a week or so) that I adjusted the idle speed. This worked for a few days then the idle was too high, so now I'm going back and forth adjusting the idle speed up and down depending on what the truck wants to do. Aggravating to say the least. I would say its the IAC valve, but I don't want to drop $300 if its something else.

So my Questions to you guys..
Is the crazy idle a symptom of the IAC valve acting up?
If not what else could it be?
Is there any alternative IAC valves that will work but doesn't cost an arm and leg?
Is there any MAF sensors that will work to convert it to a "just before the throttle body" like i'm used to so i can install an air intake?
Where can I find performance parts online that will fit?

Thanks Guys and sorry the long post!

The manual states that whenever you disconnect the ecm from the battery, you need to let it idle for ten minutes the first time you start it. This allows the ecm to run tests and make it's adjustments. Subsequent restarts should then be fine. You might want to disconnect the battery, reconnect and then try the ten minute idle to see if this helps.

Thanks I'll try that and see what it does.. Anybody else?

Has anyone else had this prob?

ok, then then has anyone successfully cleaned out the IAC valve on a 90 2.4 and can describe the process?

I would suggest going to the auto parts store and getting a $15-20 chilton or haynes manual for these trucks. It will help out a ton and you can check out the troubleshooting guide and go in order to figure out your idle problem. Sorry I only know the carbed versions of these trucks and the 2.0l eclipse motors

Wow... out of 1345 users on this forum no one can help me out with this?!

Kinda feeling like this is one of those you're on your own moments.

jeez, all I get is a "disconnect the battery" and "get a manual"... thanks guys for the replies and no offense but I was expecting somebody to be "yeah I've been there, done that and you..."

Sorry, I have a '90, '91 and a '94 MM but haven't experienced any surging as you describe. The only "bucking" I've ever experienced was at higher speeds, 50 mph and was caused by clogged injectors in an engine that had sat for a few years. From my experience with Toyotas, most surging was due to leaking vacuum lines.

Change ur MAF or clean it really good mine does it sometime and when i clean the MAF it stop till it gets dirty again. maybe this will help my truck is a 90 to BTW and all 90 model mm are weird to me cuz only 1990 eletrical will work 91 and up have simaler parts but nothin is the same my ecu went out and i like to never found one for it

First I thought about doing a top end swap to a later year, that would cover the ECU and all components, but I don't really want to sink that kind of money into it. I think for now I'll change out the fuel filter, and get a new IAC valve if I can't clean it. I checked the vacuum lines but I might change them out as well. Hopefully I can solve the problem during the process.

On the IAC valve..When I pull the top part of it, it has this white plastic screw that has white grease on it. This makes me think twice about shooting cleaner down in there, and i still have no idea how this component works.