IAC Valve on a 94 - question

[dpom]

My 94 XLT has rough cold starts. Once warm after a few minutes it runs great. After searching the forums it seems that my problem is a dirty or malfunctioning IAC valve. I cleaned the valve with electrical parts cleaner, but I stripped the two screws to take it apart so I just did my best cleaning it from outside the two holes.

The next morning the truck had a rough idle again. While the truck is idling rough, if you unplug the IAC it stalls. Once it is warm, if you unplug the IAC it still runs fine.

So I took a drive down to autozone where they tested the valve for me with a 9V battery. The plunger moves so that means it must be working. (The valve was warm)

What I would like to know is why the rough idle occurs only while the truck is cold. Is it possible that the valve is only working when it is warm or does it have nothing to do with that? Maybe I will try to take off the valve and throw it in the freezer and test it again. I would like to know that this is the problem before I lay out $70 or whatever a new one costs.

Thanks

 

[spta97]

My 94 XLT has rough cold starts. Once warm after a few minutes it runs great. After searching the forums it seems that my problem is a dirty or malfunctioning IAC valve. I cleaned the valve with electrical parts cleaner, but I stripped the two screws to take it apart so I just did my best cleaning it from outside the two holes.

The next morning the truck had a rough idle again. While the truck is idling rough, if you unplug the IAC it stalls. Once it is warm, if you unplug the IAC it still runs fine.

So I took a drive down to autozone where they tested the valve for me with a 9V battery. The plunger moves so that means it must be working. (The valve was warm)

What I would like to know is why the rough idle occurs only while the truck is cold. Is it possible that the valve is only working when it is warm or does it have nothing to do with that? Maybe I will try to take off the valve and throw it in the freezer and test it again. I would like to know that this is the problem before I lay out $70 or whatever a new one costs.

Thanks

dpom - I had a similar problem on my 2000 XLT (V8). I'm not sure what engine you have but I think the issue would be similar. The IAC is meant to adjust the air mixure and when the engine is cold it seems to have more of an effect than when it is warm. I don't think that the IAC being hot or cold has to do with it's performance, it is the engine. One way to test is unplug the IAC and see if the performance changes. If it doesn't, then it is not doing it's job.

My XLT would not stay running until the engine reached normal operating tempurature. Once it did it was ok. I tried cleaning it and it made it even worse - it would not run at all. Once I replaced the IAC (I left the battery disconnected for 10 minutes as others reccomended) the engine started right up and has been strong ever since.

Hope this helps, but my advice is to replace it.

 

[Positive Vibes]

Couln't you buy a new one, install it and see if it fixes the problem. If it does't just return the part????

 

[Rhett]

If the problem isn't your IAC, then it's something else.

Ok ok. An engine needs fuel and spark to start; make sure the fuel pump is doing it's job. Make sure the fuel filter isn't a little clogged. Make sure you don't have a vacuum leak somewhere. Make sure your air filter isn't dirty. How well is your starter functioning?

 

[dpom]

I could install a new one but the problem happens only sometimes on cold starts. It would take a few days to know if it had solved the problem. I was just curious if someone could tell me why the rough idling happens only while the engine is cold.

 

[Positive Vibes]

Rough idle could be mutliple things. Your best troubleshooting method is process of elimination. Cause you don't have any codes to lead you in the proper direction. Have you disconnected the battery to reset the ECU?

 

[dpom]

yeah no CEL, and I actually replaced the battery when I was cleaning the IAC Valve so yes. Remember after the truck warms up for a few minutes it runs smooth, and when its having trouble idling on a cold start if you unplug the IAC valve the engine stalls right out - but the valve checked out fine at the store. I think im just going to replace it.

 

[slag]

I dont know of any auto parts stores that will allow you to replace an electrical part after its been put on your vehicle.

 

[Positive Vibes]

I dont know of any auto parts stores that will allow you to replace an electrical part after its been put on your vehicle.

How would they know you installed it? Just say it was the wrong part.

 

[viewbank21]

This is a recognised problem by Ford...it is probably your intake manifold gasket (O-rings)...Do a search for OM0012 which Ford issued to all X owners for this problem