HI CAN ANYONE HERE TELL ME WHAT CONTROLS THE IDLE SPEED ON MY 93 AEROSTAR 4.0 AWD, MY PROBLEM IS THAT IT SEEMS TO ME THAT THE IDLE SPEED ON MY AEROSTAR IS A LITTLE TO LOW, IT HASNT STALLED YET BUT WHEN I AM AT A STOP LIGHT IS SEEMS TO SLOW DOWN FARTHER THAN I THINK IS SHOULD. AT NIGHT WHEN I AM STOPPED LIKE THAT THE HEADLIGHTS SEEM TO DIM ALITTLE TILL I START OFF AGAIN AND I HAVE NOTICED THAT MY CHARGING GUAGE MOVES BACK BUT NOT OUT OF THE NORMAL RANGE, COULD IT BE POSSIBLE TO CHANGE THE THROTTLE POSITION SENSOR AND THAT WOULD MAKE THE IDLE SPEED COME BACK UP TO WHAT I THINK IT SHOULD ME. I HAVE JUST ACQUIRED THE VAN IT HAS 97,000 MILES ON IT AND IS IN VERY GOOD CONDITION, IT HAS PLENTY OF GET UP AND GO WHEN I NEED TO DO THAT AND IF I HOLD THE GAS PETAL DOWN JUST A LITTLE WHEN STOPPED IT IDLES FINE. DO YOU THINK THAT IT WOULD HELP TO HAVE THE FUEL INJECTORS CLEANED ALSO OTHER THAN THIS PROBLEM AND THE DAMNED CLOCKSPRING IN THE STEERING WHEEL IS BAD (TO WHICH I HAVE BOUGHT A NEW ONE JUST HAVENT GOTTEN THE NERVE TO CHANGE IT YET) THE VAN IS THE BEST SO FAR SO ANY HELP WOULD BE VERY THANKFUL


93 FORD AEROSTAR 4.0 ELECTRONIC 4WD
78 JEEP CJ7 258 CU IN 1 BBL ( FOR SALE )

 

The IAC (idle air control) is A round thing about 1' diamiter and about 3' long with 2 wires pluged into the end of it and its by the throttle body. If you think thats the problem then disconnect the plug on it with the engine running and see if the idle speed goes way down (engine shouldnt stall but will idle real low). if idle speed dosent change then the IAC is the problem.

hope this helps

 

[font size="1" color="#FF0000"]LAST EDITED ON 25-Feb-01 AT 08:51 PM (EST)[/font][p]PS You can try to clean the the IAC. Disconnect the big air pipe and with the engine running, spray carb cleaner into the hole that goes to the IAC. You may want to take the plastic cover off the TB (throttle body). On my '93 4.0L engine its held on by 2 5/16' bolts and may require the air hose to be removed from TB (needs to be removed anyways) to get it out, but air hose needs to be removed to clean IAC. DO NOT SPRAY CARB CLEANER INTO THE AIR CLEANER BECAUSE MAF(sensor on air box) WILL GET SCREWED UP.

With the TB cover off you can rev the engine up from under the hood to keep the engine running while spraying the cleaner.

Let me know if you have any questions.



PS, this thing I call IAC the Haynes manual calls the ISC (idle speed control). It is the same thing

 

I am just curious if this is the same on the 3L. I just had to replace the in tank fuel pump and the relay. Now my van in idling to the moon. I was told it may be a vacume leak but I checked and couldn't find anything. I unpluged the (what I think is the ICU) and there was no drop in idle. could this be my problem, I was also told it may be the ecu relay so I am getting one tomorrow to try it. any help would be great,
Thanks,
Sean

 

I meant IAC lol

 

OK PyroManiak thanks for the advice but I have another question if I unplug the IDC and the idle stays the same then the IAC is the problem, right, wouldnt it be better to replace it than to try to clean it beng that it has almost a 100,000 miles on it and has probably never been cleaned or replaced and if I did decide to try to clean it, what plastic cover are you talking about the big plastic air hose that is attached to the throttle body with a hose clamp or the cover to the left of the throttle body,if that is it, I think that mine is metal and not plastic, it is kinda flat and is right beside the throttle body to the left, does it cover the TPS if not I am lost (as usual) I have a chiltons manual and it shows the IAC on top and the TPS on the left side of the throttle body, Does a new IAC cost alot(like the clockspring for the steering wheel) let me know and thanks for the help also can an IAC be bought anywhere or does it have to come from the dealer also

 

Well apparently on the 3L it is called the air bypass valve. I took this off and cleaned it to the best of my ability and reinstalled it. There was no difference still. It still idles high. Is there a way to check the ohm reading of the valve to see if it is good? I imagine that is all it is is a coil in there and when voltage is applied it pulls the valev closed. Does it run right off of 12volts so I can try it with a battery charger?I need help ASAP before I kill somone cause of the lack of braking on slippery icey roads
thanks,
Sean

 

You need to set the base idle with the ISC wire connector disconnected. A lot of times the idle speed is adjusted to compensate for a dirty IAC. Then when the IAC is cleaned or replaced it can't control the idle because it's already too high.

 

Well I just replaced the air bypass valve and now it runs fine.