Setting Base Idle

I am having IAC problems so I am going to set the Base Idle. I had a few questions. Also get a Code 12 with KOER. Im sure the idle have never been touched since it came out of the factroy I am the 2nd owner and he was not one to touch anything under the hood still had Air Sliencer! Its a '89 with 68K 5-Speed. CIA, MSD 6A, only things done to engine. Throttle body has been off for cleaning already. This is not a new issue just wont go away. I am close to buying Ford Replacement IAC, I was cheap and got a aftermarket one and it wont work upside down.

1. Do I set it at all with the IAC unplugged as it dies the second it is unplugged? I see where it said to do that on the Surging Idle Check List. And how do I do that have someone in the car with foot on gas when I unplug it?

Or do I set it with it plugged in?

2. What voltage should the TPS and IAC valve be for proper operation? And to set the TPS just turn the screws?

3. Do I need to clear the KAM? And how?


Thanks for all the advice guys this message board is great.
 
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I can answer a couple of your Q's. The voltages I don't remember right off bat.. someone like HISSIN would recall.

To set base idle, unplug the IAC. If it stalls doing this, first turn the screw clockwise a couple turns so the thottle is open a tad bit more. The engine should be fully warmed up also, so no cold idle adjustments. Disconnect, then turn screw til idle sits steady at 750 rpm. Shut off engine, then plug IAC back in. Base is now set.

It probably would be a good idea to clear KAM. Otherrwise it will have stored codes from the IAC removal and previous adjustments may give an incorrect calibration. Remove battery cable for 2 minute. I sometimes had to leave it for 5 minutes just because there was residual components keeping the KAM afloat longer. Re-connect battery, start and let idle for about 10 minutes. Do NOT mess with the throttle or touch anything that may interferre with the learning process. After 10 minutes, take it out for a drive so it can better calibrate the TPS and set AF ratios. Just helps it run a little better in the long run.

I'm not sure about the TPS. It has a slot in the middle that the throttle plate turns by twisting a flat stem inside the TPS to rotate it. It retracts back to it's set position so I honestly don't know how they done it. I once bought a replacement TPS (which is the current one I have) , it has 3 screw hole positions on each side. I think you set it by removing the screws and re-inserting it in by either 15 degrees couterclockwise or 15 degrees clockwise. Its normally set in the center position, which is stock. Why do you need to adjust it?
 
Ok,, thats what I was looking for. I will do that ASAP.

The reason for the the TPS question is some people on here say it might be out of range to. But I will set the base idle and try that first. Im betting its to low then the IAC has to over correct to so much that it takes the computer so long to learn how to compensate for it.

Once again great advice on here.
 
There are several methods for setting the idle. I do it as MustangLX-5.0 noted however. Mods and the state of tune can dictate which methods work.

Do be sure the engine is fully hot and all accessories are turned off before you set the idle.


As said, don't sweat the TPS. If it's out of range, it will log a code. If you really wanna check it, just make sure it's in the ~0.60 - 1.20 V range (KOEO). If outside that at idle (or KOEO), it should generate a code.

For the KAM, just disconnect the battery and turn on the headlights for 30 seconds. That'll discharge the capacitors. Turn off lights off and reconnect the battery.

I would mark the adjusters and take notes of all changes you make. That way you can get it back to how it was if you need to. Sometimes people end up out in left field because they change the timing, idle setting, get or fix a vacuum leak, have a dirty IAC, etc etc. Logging all changes is a good idea.

Do you have a decent cold idle (at or over 1K RPM initially)? Does the idle kick up a little when you turn on the AC? If no to both, the IAC is likely not doing too hot. You could try to clean your old one (always assume if you clean it, it will crap out though. Sometimes they get worse after a cleaning).

I use WD-40 and then electrical contact cleaner to clean them. They can get pretty coked up inside. Let it marinate with the WD or cleaner for awhile, rinse and repeat. A cotton swab can help remove sludge.

Good luck.
 
All,,,

You guys rock! It runs like a champ now! The idle screw was complety out of adjustment had to turn it around 5-7 times just to get it to run then turned it down to 600 RPM. Cleared the KAM and it runs like a champ now.

Once again thanks guys. Id buy you all a drink if I could!
 
I can answer a couple of your Q's. The voltages I don't remember right off bat.. someone like HISSIN would recall.

To set base idle, unplug the IAC. If it stalls doing this, first turn the screw clockwise a couple turns so the thottle is open a tad bit more. The engine should be fully warmed up also, so no cold idle adjustments. Disconnect, then turn screw til idle sits steady at 750 rpm. Shut off engine, then plug IAC back in. Base is now set.

Your talking of the actual throttle plate adjust screw on the TB here?