Okay I have narrowed the problem down a little bit more. On the heater side the motor will only rev when the defrost option is on. When climate control is on the cold side it will not rev up unless you select defrost or if you turn the ac on.

 

Well, if you disconnect that vacuum run, plug the motor side, and moving the controls around doesn't affect the engine speed - but connect the vacuum to the HVAC controls and it DOES affect engine speed - it's pretty much somewhere between where you disconnect it and the ends of the vacuum lines *grins* So the next step is to check everything downstream of the HVAC control unit.

RwP

 

Alright I messed with it today and now I'm stumped. I put my finger on the nipple that the vacum line goes onto that is on the engine and had someone kick the ac on and it still revved way up and did not go back down even tho I had the whole port blocked off. So what am I looking at now more of an electrical issue?

 

Not quite. If it's still kicking up, either the ECU is over-demanding more throttle, or the IAC is letting more air through and the ECU is compensating with more fuel.

So ... time to check the IAC, or even replace it.

After that, it's time to see what the ECU is doing with the IAC.

note: If there's any A/C demanded, the ECU should add a bit more idle air (via the IAC) and fuel (slightly more injector duty cycle) to compensate for the load. If done 100% properly, the driver never notices.

RwP

 

The IAC is probably right at a year old. It's the better quality one from O'Reillys. How would I go about pinpointing the exact issue without throwing a new IAC on ? I'd rather not just throw parts at it. And I know for a fact that the IAC is being opened way up BC when the engine revs up u can hear a major suction of air going through the IAC. But why is it doing that when I turn the ac on is what I'm trying to pinpoint.

 

Check the voltage to it.

However, from the forums around, it appears that all the third-party IACs for the Magnums, well, don't quite suck right *grins* (Joke - they're supposed to suck but under ECU control.)

The two choices are that the IAC is bad, or the ECU is feeding too much voltage. At this point I'd check the Factory Service Manual for the way to test which it is.

For 1995, alas, it specifies using the DRB and a special exerciser. Without that, you may have to pick up a IAC and swap it.

And why is it doing that? Because, if the IAC didn't open, the load from the A/C compressor would bog the motor down and stall it.

One MORE thing to check - the IAC gasket. Make sure that all the bolts holding it on are snug, and that the gasket is in good shape.

RwP

 

I know the IAC should open up BC of that but it shouldn't be that much for sure lol. And ive heard third party tps sensors for these trucks have issues but I didn't know about the IACs having issues. And I think that IAC only has a rubber o ring on it. I don't remember seeing a gasket. I will check the service manual to see how to test them both and then I will see where I am after I do that. If the ECU is feeding to much voltage then where should that lead me to check next?

 

If the ECU itself is feeding too much voltage, there's not much else to do but swap the ECU.

Hence why I'd pay for a dealer to run the DRB test on it first.

(Well, !I! wouldn't, my nephew is a service writer, I'd get him to "borrow" the stuff and do it over the weekend ... but not everyone is as lucky as I am in that respect.)

RwP

 

Well you have a very useful asset lol. One thing I have noticed is that while I am turning the ac on and off to try to get it to rev up eventually it quits doing it and I have to wait awhile before it will do it again

 

Well after testing today and everything checking out okay I happened to grab ahold of one of the wire connectors on the passenger side above the firewall and the truck immediately started reving up so I set it back down and it instantly quit. Did this multiple times with same result so I would say that I have a loose or worn out connection in that plug. I think I can fix it from here. Thanks so much for your input man!!