my wife's 97 is having problems

[dmyers87]

Hopefully someone can point me in the right direction for this problem. It's a 97 explorer sport 4x4 with a 4.0 sohc & has 167xxx. Starts up fine, idles fine as long as the heat isn't on. Now when the heat is on & its idleing, for a few seconds it'll be at about 750-800rpm, and then ill hear what sounds like the ac compressor on and it'll come down to about 500rpm then after a few more seconds it'll come back up. It does this continously, but only with the heat on. My wife was about to leave for work tonight & it was doing it, so she reved the engine up a bit, and it died when she let off the gas, but it fired right back up thankfully. Later today I'm gonna unplug the ac pump & make sure that it is making the noise I'm hearing, but still wondering what is causing this. Anyone have any ideas on where to start? Help please & thanks in advance

 

[SoNic67]

IAC valve. Easy to replace, don't bother to 'clean it up'. It will start to be worse and worse if not replaced.

 

[dmyers87]

The IAC is causing my engine to do this but only with the heater on? Now is there a way that can be tested? I just looked & the parts store has it for $100 and we ain't got money to spend like that.

 

[2000StreetRod]

A/C compressor on

The PCM controls the activation of the A/C compressor and adjusts the idle to compensate for the additional engine load. The A/C compressor is activated in all climate control mode selector positions except panel, off and floor when the outside air temperature is 50 degrees F or greater. Try selecting floor or panel for heat until you fix the idle problem.

 

[dmyers87]

wife just got home. Said it was doing it when she got out of work & it was like 40 degrees outside & its actually doing it when the control knob is in any position. I doono if that makes a difference or not, but might be helpful

 

[SoNic67]

I guess you will wait to replace the valve till your wife gonna get stuck somwhere and then you will pay for a towing truck too...

 

[dmyers87]

Glad AAA has my towing bill for 100 miles, but I was wrong about the controls. It doesn't do it while on panel or floor. So I guess a pcm is my problem, where can ya get one cheep?

 

[koda2000]

Glad AAA has my towing bill for 100 miles, but I was wrong about the controls. It doesn't do it while on panel or floor. So I guess a pcm is my problem, where can ya get one cheep?

what? how did you come to this conclusion? it's probably the IAC valve. it can easily be removed and you can try cleaning it (may not help, but may) for next to nothing. and it can be tested (if you have volt/ohm meter) to see if it's working from an electronic standpoint. if you really want to just throw your money away, get a new pcm first.

 

[2000StreetRod]

Not the PCM

. . . I was wrong about the controls. It doesn't do it while on panel or floor. So I guess a pcm is my problem, where can ya get one cheep?

I doubt that there is a problem with the PCM. I was just explaining how the climate control system works. You may have a problem with the air temperature sensor if the A/C compressor is activated below 50 degrees. Check your owner's guide to see if your system works the same as my 2000. I think my PCM uses the intake air temperature (IAT) sensor to measure outside air. If the IAT sensor is bad then the air/fuel mixture will be off which can affect idle. I think cleaning the IAC valve and then the MAF sensor would be a good and inexpensive start to solving the problem.

 

[SoNic67]

I suggested the IAC valve in the second post. You did it also right after that.
I guess, he doesn't read any answers.

 

[dmyers87]

So I cleaned it, it worked for a cpl mins then went back to what it was. The iac is now replaced (now that I had the money to get it). When I had the old one off I cleaned the ports going to the IAC and found a bit of oil in the back port. Is this normal or is there some other seal shot?

 

[littlezell]

it is normal from what I have read....

 

[kindred4x]

The AC Compressor in the 97 is failing, which leads to it seizing when running, which will slow down your serpentine belt to aid bad idle stalling condition.

When the heat is on the HVAC system will cycle the air conditioning system on and off.

This is due to humidity and condensation within the cabin. A cold evaporator coil(AC) will pull moisture out of the air and drain the water outside. Just like a hot day in the summer when you see puddles of water under your truck... that water is humidity in the air being dumped outside.

So in the winter when the heat is on the cabin needs to rid of humidity in the cabin so your windshield does not fog up, that is when the AC compreesor kicks on for some time to collect the humidity and dump it outside. The compressor will kick on and off when heat is on. Especially during the defrost option.

With my experience I believe that is whats happening. On my 96 I have a seized AC compressor, with out the fuse pulled, heat on my truck will literally bog down so much that it dies when the AC compressor kicks on, and smokes the belt. I pulled the fuse and now my truck runs fine with the heat on

 

[dmyers87]

Kindred, thanks for explaining why the AC kicks on & off. I replaced the IAC, and it didn't bog down so bad but I was still tryin to figure it out. Now I can answer my wife's question about that without saying " I doono, but thats how it's supposed to work" lol. I hate having to say that. Now, I've replaced the alternator, lower ball joints, idler pulley, water pump, tires & have the ac pump from a 00 sitting here for when the one in it fails, & when it does, out come the tools. How much freeon should I put in the system when i replace the pump? I got one small can here, but i know i should use more, just doono how much

 

[kindred4x]

Kindred, thanks for explaining why the AC kicks on & off. I replaced the IAC, and it didn't bog down so bad but I was still tryin to figure it out. Now I can answer my wife's question about that without saying " I doono, but thats how it's supposed to work" lol. I hate having to say that. Now, I've replaced the alternator, lower ball joints, idler pulley, water pump, tires & have the ac pump from a 00 sitting here for when the one in it fails, & when it does, out come the tools. How much freeon should I put in the system when i replace the pump? I got one small can here, but i know i should use more, just doono how much

Have you pulled the fuse for the compressor to see if your idle is better with the heat on?

Changing a comprssor takes some special tools. The EPA has banned the release of refrigerant(freon) into the atmosphere, and will pay up to 10000.00 dollars for people telling on others.

First you would have to recover the refrigerant into a approved container, using a approved recovery machine. Then pay bucks to dispose of the refrigerant.
Then you would do your compressor swap. After replacing parts you would pressurize the system with dry nitrogen to find leaks and flush out the system.
If no leaks are present the next step would to pull the system down into a vacuum, using a good vacuum pump and vacuum gauge. 500 microns is standard for the HVAC industry, automotive may be different. The reason to pull a vacuum is to remove any air and moisture from the system. Nothing is worse than having air and moisture in your system. After the vacuum is achieved hopefully you can find how many ounces of refrigerant the system will hold and charge the refrigerant in as a liquid due to temperature glide of mixed refrigerants like 134a. Charging as a liquid is dangerous. You can scramble the compressor(like pouring water into a running motor.)
Maybe a automotive hvac guy will chime in, because all my info is based on my training and work for residential, commercial, HVAC and refrigeration

 

[Thuggsy]

anyone have any info on what wire to cut so that HEAT doesnt engage the AC compressor?

 

[kindred4x]

anyone have any info on what wire to cut so that HEAT doesnt engage the AC compressor?

the fuse panel located to the left of your steering wheel( sitting in the car) contains the fuse for the AC compressor. I pulled mine out and threw it in the glove box. Do you have the owners manual? It will tell you what fuse to pull. If not I can take a look at mine and let ya know

 

[sport97]

My a/c compressor was low on freon so i used to pull the fuse. Now the system as no freon so it doesn't even kick on the compressor. I'd pull the fuse and see what it does then.

I also have a weird idle that causes it to stall, i used to think it was only due to the heat but the compressor doesn't kick in because its so low on freon. It will get a surging idle that drops low (just like it used to do with the heat/ac) and I can even force it to stall by shifting to reverse, pushing the window buttons or putting any load on the power steering. I even had a girl look at me once when it happened and asked "did you just stall an automatic?"...

 

[Thuggsy]

the fuse panel located to the left of your steering wheel( sitting in the car) contains the fuse for the AC compressor. I pulled mine out and threw it in the glove box. Do you have the owners manual? It will tell you what fuse to pull. If not I can take a look at mine and let ya know

thx

but i dont want to disable the compressor, just want to disable heat engaging the compressor.

 

[dmyers87]

Well I didn't realize there was so much to replacing the compressor. Only problem I'm having is that the clutch on my ac pump is going out & I figured it'd bee easier to change the pump as opposed to the clutch. Anyone know how difficult it is to change the clutch? I got a whole other pump off a 2000, so the parts are here already, just no knowlege lol.