A/C want kick up idle on my '88 Mark VII

Anyone know what could be the reason why when I turn on my A/C it dont kick up the idle?
Thanks

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Mach 1 wrote:

IAC valve needs cleaning.
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If the iac needs cleaning then it wouldn't idle up when the motor is cold. And it does that fine.
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88...hmmm Is that CFI? Does it have an idle kicker motor? You say it idles a little higher when cold? Could be the ECU dosent know the ac is on, it is also possible that it doesnt care....Maybe you should post what engine, fuel injection type for us....might help.
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Maybe we're getting it wrong.
If it didnt "kick up" the idle, the rev's would drop.
If they stay the same it's working.
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I suppose it would help to tell about the motor.
Its a 5.O HO EFI just like the Mustangs. It is the speed density also. No mass air sensor. They have the EEC IIV computer in them.
Anyway the thing idles up when its cold like it should. So that tells me the iac is working. Im sure theres some sensor that is supposed to tell the iac to bring up the idle when the A/C comes on.
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4ax.com:

Does the idle stay the same or does it drop?
Just answer that.
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It drops after about 15 seconds or so. Always has on first startup.
But when I hit the A/C button the idle dont kickup so in turn the idle is to low due to the extra drag of the compressor. Its got to be a signal not getting back to the EEC.
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Mach 1 wrote:

Try disconnecting the IAC valve input and then start the AC. If the RPM then drops or the engine dies, then the IACV is obviously working.
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Humm.....not a bad idea. God I dread trying it. Its so dang HOT outside.
wrote:

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If it has idle problems, clean throttle bore and IAC. Then take it for a ride so it can re-learn to its new, clean self. Normally (on newer vehicles) the computer actually controlls the AC compressor, I kind of doubt it on the eeeK 3 though, the AC compressor probably sends the 12v sig to the ECM. It should keep the idle steady when the AC is on, it's put in drive or rev, hit the cig lighter, ect. not really "kick it up" .
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Aaargghh! I dont understand this whole thing!
The 88 is full EECIV. On ANY I've ever owned or seen the idle stays constant A/C clutch on or off! It's a V8 so it should be about 600-650 RPM
I think our friend is used to carb type "kickers"

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I think you are dead on backyard.
Just so Mach 1 knows, you can generate a code during the KOER test by leaving the AC ON during the test. The test wants you to turn off the AC. If you leave it on during the test it will set a code for seeing the AC on. That is how you could check to see if it knows when the AC is on. BTW, if it sees a idle control problem it will set a code for that too. Also, clean the throttle bore so your minimum air is correct again.
Does the car have a real drivability problem? Not sure...
Is the horse dead yet? I think so.....
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No drivability problems except I have not been using the A/C afraid that the motor will die in traffic.
I didnt get a chance to try anything yesterday. You have a good point about starting tests while A/C is on. Fortunatly I have a complete emmissions book from Helms which is good for tracking down defective sensors.
I did spray carb cleaner into the intake right at the butterfly and also into the iac port. Im thinking I will take iac completely off and do a more though cleaning.
I read that a map sensor could be at fault also. Possibly some vacumn hoses leaking too.
And its possibile the idle rpm is just to low to begin with.
On Tue, 16 Aug 2005 06:52:04 GMT, "Shoe Salesman"

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Yes, it could be too low because the throttle bore is dirty. If no one has messed with the idle screw it will be back to normal. There is most likely a minimum air procedure to set it by the book, follow it closely if so. But I would first clean the IAC and bore well. Then drive it with the air on for a while and see what it does. If it dies at first give it a chance for a few stop and goes. If it keeps dieing, set the minimum air. If it still dies I would replace the IAC. You could skip to the last step (replace IAC) and it will probably fix it. Since you have the book it would be good to follow it by symptom (low/erratic idle or something similar), try to understand WHY you are doing each step,that way it will teach you allot about EEC4 Fords- that's for sure. It kind of amazing really, if you follow the steps exactly in the book, the car will diagnose itself. Good luck
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Its been well worth the money I paid for the emmissions book. It explains how to set the base idle. I also did a code read and it showed a 32 which is the EGR sensor.
I guess a step at a time.
And now it looks like Im going to have to tear the dash out now. My climate control is showing a code that the defroster door isnt working. And sure enough, it want blow air up thru it. I had to do this once before replacing the heater core. Talk about a nightmare.

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or not) would cause idle problems. It was like they rigged the thing to idle rough so you would take it in. (No kidding) And remember I said the EGR did NOT have to leak. A common problem was the sensor that is mounted on top of the EGR (position sensor) would read the valve was slightly open. The fix was to grind about a 1/16 to 1/8 of an inch off of the tip of the sensor pintle. Clear the codes and re-run the self tests. If no codes, ....fixed. Remember to run the KOEO first, fix any codes there, then go to the KOER. Also, fix codes in numerical order, low number first. Bottom line, if you have codes fix it, it will probably fix your idle problem.
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Or make a spacer to hold the sensor out just a bit just to see.
I worked 5 1/2 hours last night tearing out the dash. And its still not all back in. My god, I would hate to see what a dealer would charge to do this. It is one job I dont want anyone to have to experence.
And after all that, the motor I was checking works ok when wired directly to 12v. Dammit.
On Wed, 17 Aug 2005 12:32:42 GMT, "Shoe Salesman"

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Mach 1 wrote:

The actuator has 5 wires, 2 for the motor and 3 for the feedback circuit. It's the feedback potentiometer that usually fails. The motor will operate normally but the EATC controller doesn't know what position the door is in. The blend door actuator on my 84 Mark has an open feedback pot. It sets a code in the EATC but it works normally as far as I can tell. IIRC the blend actuator and the mode actuator are the same. If you know the blend actuator is good, swap them. The blend actuator is accessable without removing the inst. panel. I've had my inst panel out twice. Loads of fun.
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Well there is no way you can get to that door without removing the entire dash. I know, I spent 3 hours removing the dash and console, and I spent another 5 hours reinstalling then another 2 hours yesterday still installing and Im still not done.
I removed the motor that opens and closes that door and connected it to the battery and it worked fine, dammit. So, anyway it appears to be working now its back togeather. Maybe just the fact that I tore into all this made something work, I dont know.
I do know I have really enjoyed this car, its just got way to many things under the dash. Trust me I have pictures.
On Thu, 18 Aug 2005 17:33:02 -0400, Tom Adkins

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