RPMs drop when heat is on? Help

[headrush]

I drive a '97 XLT, 4.0 SOHC.

Lately when sitting at idle (like a stoplight), my RPMs start bouncing in between nearly 0 and 1,000, and when I turn my heat on, it drops considerably, to the point where the vehicle almost cuts off (it'll start chugging and the gauge lights flicker, and then the RPMs go back up again, bouncing back and forth). Also, when I got back to my house today, while going from Drive to Park, it just cut off completely. Thing is, it starts up just fine, my vehicle just seems to have these problems when its been running.

I cleaned my IAC valve but have yet to clean the MAF sensor, could either of these be the problem or could it be something else?

Any help soon would be greatly appreciated.

-Cliff

 

[headrush]

Please help...ANYBODY???

 

[Charlie]

I would suspect that it is the IAC. If cleaning it didn't work, you may want to consider replacing it. I think this rather than the MAF because it sounds like it is running fine other than in idle. Also, maybe your TPS isn't adjusted properly.

 

[headrush]

I've got a good bit of miles on my vehicle, so I guess it's possible that the IAC needs replacing. Is there any possible visual evidence that the IAC has gone bad, and if so, what determines it?

The key thing here is that when I turn my HEAT on, with the engine running, stopped in Drive, that's when my vehicle starts to chug and feels like its about to cut off. It does the similar thing when I shift from D to P, the RPMs drop considerably, and then climb up again, back and forth.

Anyone else had a similar problem like this?

Thanks.

 

[BLKLTDV8]

When you turn on the heat the A/C compressor also engages. This is what's causing your RPM's to drop. Sounds like your IAC has crapped out. I've had to replace them even though they were spotless. Try that first.

 

[headrush]

Ok so now I'm looking to buy a replacement IAC. I just ordered one from RockAuto for around $70, but I was looking at Advance Auto/Kragen (both Parts America places), and theres an IAC that Niehoff Ignition makes, with the same description of an IAC valve. However, one's 101.99 or something and the other is 39.99? Does anyone know what the difference could be? For curiosity's sake, when I added the cheaper one to the cart it mentioned something about idle speed control? Thanks guys for your help, you're a lifesaver!

Link with the two parts:

http://www.partsamerica.com/ProductList.aspx?PartType=506&PTSet=A

 

[scucci]

97 and 98 use the one with a breather filter -black plastic knob on an angle. 99 up use one without the breather which is less expensive.I ordered my 98's on line for $90.00 and my friends 2000 expy I got at autozone for 39.99. They also have different shaped ports. I have heard that some IAC's have the filter at the wrong angle - I have not verified it. There is a part number on your IAC - I went to car parts.com to cross reference this to a bosch number and got the correct one.

Hope this helps
Scucci

 

[scucci]

In reading your originalcomplaint,it sounds as though you might have a vacuum leak at the heater control valve.

Just a thought.
Scucci

 

[ThePhoenix]

we should start a thread of common parts like the IAC and MAS and the best place to buy them...based on our experiences...you know, for reference

 

[headrush]

Well I got a reply email back Parts America, which wasn't really any help, they told me to just contact Niehoff Ignition to see what specific part it was, but by that time I had received my new IAC valve from RockAuto. Funny thing is, it's an AC Delco (I always think GM when I see it), and it was manufactured in Japan. Go figure.

I will do an install once time and daylight allows and the weather warms up later in the week, will let you know how it goes.

P.S. Still wondering about the heater control valve, anybody have any tips on repair or any similar problems? I purchased a new IAC due in part to the high mileage on my vehicle, I figure it would have crapped out eventually.

 

[headrush]

Well the weather warmed up and I was able to replace my old IAC valve with the one I received from RockAuto. It seems to run a lot smoother now and doesn't run rough or when my heat and a/c are turned on, and my RPMs don't plummet when idle, knock on wood.

I also purchased a replacement power passenger's side view mirror and hood support lifts from RockAuto, both which came today (Saturday), which I was psyched about. I put in the side view mirror and will do the hood lifts later. Right now a thick piece of bamboo is my hood prop .

Thanks again guys for the help.