IAC Solenoid on the 5.0

[skullandbones]

I've been focused on the engine bay for a while now and I came to the conclusion that I have been overlooking one item that I knew nothing about first hand. So I removed the Idle Air Control Solenoid or (IAC). BTW: Ford officially calls this an Idle Speed Control Motor (ISC). The first thing I noticed is the internal parts were covered with a greasy slim for lack of a better term. I was expecting it to be caked on hard sludge. It cleaned off pretty easily with a mild detergent/water. I didn't want to completely disassemble the spring/valve component (similar to an accelerator pump in carb). It appeared to be operating by applying air to the correct orifice and actuating the valve assembly by hand. So the black sludge was not causing the valve to stick or plugging up any air passages. Mine is the type that gets air from the cold air stream and lets it bypass the TB butterfly by engaging the solenoid at different lengths. It's not an all or none type process. I believe the PCM counts the number of ignition pulses from the TPI and other inputs like temp to determine the necessary added air during warm up. My concern was that the sludge on the valve was affecting the air flow even if not cutting it off or causing it to fail for smooth idle. When I did get it completely clean, it looked almost new. The valve assembly worked very smoothly. I also checked the "motor" or solenoid by doing a resistance check. It was 10 ohms which was acceptable (between 7 and 13). I don't know if it is possible to remove the assembly and check it while it is running. Don't know if you would be able to see small movements of the valve. Anyway, the cleaning and checking was pretty straight forward.

I polished the two outer bodies while I had it broken down. It's one of those things I was thinking about removing until I realized that it may have a very necessary purpose. I did run it unconnected but I don't think that's the same as removing it completely. I suppose it acts like a choke on the carb but after polishing it up, it actually looks pretty good. If you were drag racing, it probably could be dispensed with but for drivability, I guess it is one of those assets of the EFI that you want to keep.

Results: I found that the surge I had experienced from day one which is quite common in the Mustang discussions on the 5.0, has decreased from a range of about 5k down to 1K. I'm thinking that even though the black greasy substance was not caked or solidified to the valve and openings, it was probably affecting the air flow some. The best explanation I can find is that the PCV flow can cause this build up over time. Don't know if the build up was from the time I started the engine or if it was there before since it was a donor item. I suppose the only solution is to delete the PCV or add this process to the maintenance as I have been doing with the TB opening now and then. Now I will remove and clean this device as well. It only takes a few minutes to disassemble and clean.

Have any of you experienced any issues with this item or is it just one of those things that goes unnoticed?

Thanks,

WEK.:cool::cool::cool:

[Avalanche325]

I had to replace one, but not on a 5.0. It was on a Ford Mondeo (Contour here). Cleaning it worked, but not for long.

What would you do if you deleted the PCV? EFI is usually not too happy with unmetered air.

[skullandbones]

Avalanche,

The PCV, as far as I know, is not absolutely necessary from a strictly operational perspective. I think it is a very crude way of reburning crankcase gases. However, I don't know if that is beneficial for performance by reducing detonation tendencies some. As far as the ISC on my 5.0, it gets it's air supply from the metered cold air system (MAF). I may have miss understood. How do you mean "unmetered"? I agree about it lasting for a limited amount of time. I think this will have to be cleaned on a regular basis. The idea of deleting the PCV was to take away the source of the contamination. Thanks, WEK.

[Jeff Kleiner]

The PCV introduces crankcase air into the intake after the IAC (ISC). They are not related.

Jeff

[CraigS]

It is pretty common for IACs on many efi cars to have the same problem yours did. They get gunked up and don't move freely. At Lexus we had one model that was more problematic than others. For a couple of years we took them off and cleaned them as you did. Unfortunately that turned out to be a temporary fix in too many cases. When the car came back 3 months later we usually had to do the replacement for free. Soon we started to replace them on the first trip to the dealer. Since your own labor is free, I'd reinstall it and see how it works. Primarily the IAC is thought of as regulating the idle speed in response to temperature, AC on or off etc. It needs to move freely or you get problems where the idle drops to near a stall, the IAC tries to open, sticks for a bit, than slams open and the idle comes up to too high an rpm. And back and forth. It is also the piece that allows the car to start correctly when cold. When they start sticking, hard cold starting happens because they don't open enough while cranking. If you can help it start by giving maybe 1/4 throttle, that is usually an IAC problem. See how yours works over the next few months. good luck.

[skullandbones]

http://img.photobucket.com/albums/v461/hippieblur/Stff/DSCN0770.jpg

I have my PCV plumbed like this. I must admit I don't have the experience of years of working on these engines so I may have it plumbed wrong (pre TB butterfly). However, I have seen many like this.

Jeff, I know these systems are not related but I think there can be some contamination from the PCV crankcase stream. I've read a lot of threads related to this where they talk about the PCV causing a build up on the ISC inerds and intake. I don't know whether to DC the PCV for some other version of venting system, leave it as is, or replumb it post TB butterfly. What experience I have had with these devices has shown me that the TB will eventually start getting a film of oil and associated particules over time in OEM setups. I have cleaned my share of these which usually improves the smoothness in idle and similar situations like Craig S described. This is the first time I have taken the ISC apart to clean. From what Craig S said, this may be very sensitive and require a regular PM which I am willing to add to the list. I haven't had a chance to drive this week to really get a feel for any changes in idling or surging. Also, I don't have a breather installed in the system. The ISC gets it's air from an orifice opening on the pre TB butterfly in the cold air air stream and another one delivering added air to the post TB butterfly side. it is not vented to the outside.

Thanks,

WEK.

[Mike N]

Bill.

Did you try 're-centering' the IAC? Warm your engine up completely then turn it off and unplug the IAC. Restart the engine and adjust the idle to what you want. Shut the motor off and plug the IAC back in again. Restart the engine. The IAC needs to be in the middle of it's range under normal conditions so that it has room to adjust the idle up or down as needed. Sometimes it gets biased one way and the EEC cannot make the adjustments it's trying to make.

The PCV should be plumbed before the throttle blade but after the MAF sensor.

[skullandbones]

Mike: I will do that tomorrow. I have had the pleasure of changing out my water pump for the third time. The first was a rebuilt one which lasted for 1K. This new one only lasted for 1.6K so even though I have a guarantee, it still entails extra work. I changed out the water pump pulley with a new one as it appeared to be just slightly out of round. It wasn't much but I figured it could have caused the bearing to wear and cause the banshee like squealing that occurred. I have not heard of what you describe before but it makes sense to calibrate the motor to the right position.

I'll let you all know if this makes a significant difference when just driving normally. It might help someone later. Thanks, WEK.

[DaleG]

Something for your notebook: tried to download attachment, but file is too large, so PM your e-mail address and I'll send you stuff on 5.0 EFI tuning (includes IAC) and other "nice to be aware of" stuff.

Cheers, Dale

[skullandbones]

Will do, Dale. Thanks, WEK.