First off, nice forum you folks have here.

Secondly, I HAVE searched and sorted through a lot of the idle issue threads, but none of the above really relate to my issue.

I will go ahead and give as much background as I can to help everyone better understand.

Info: The truck has 198,000 miles on it. I had 3 codes being thrown: EGR code (can't remember the code off the top of my head), a P0171, and a P0174. We noticed 2 hoses for the EGR were pretty shot, so we replaced those yesterday as well as putting on a new gasket for the oil filter adapter plate and a new power steering pressure line. After replacing the EGR hoses, we cleared the codes, and this morning on my way to work the SES light came back on. I have yet to get home and scan it, so I will update later with the current/new codes it is throwing.

Now, my REAL problem is that when I first start the truck on cold mornings (only cold mornings), the idle surges horribly. Around 500 up to 1500, and right back down to 500. It repeats this process like a loop until I put the truck in reverse/drive. Now this is where I can't find any related information: With the truck in drive, it drives just fine...BUT, when I come to a stop light/stop sign and let it idle for a few seconds (still in drive mind you) the truck will surge to 2000 rpm and then just fall flat on it's face and die. Put it in neutral, restart it, wait for light to change and then put it in gear and go. When I arrive at my destination, I put it in park, and it just dies on it's own. I figured (like many of you will) that it is the IAC. I pulled it last night, and while LIGHTLY using a screwdriver noticed the valve/spring was frozen up. Sprayed the **** out of it with carb cleaner, let it dry, bolted it back up, and the same problem still exists. To make sure it is not a faulty/dead unit, I will be picking up a new IAC this evening and installing. I do want to point out that this only happens on COLD days. Anything above 35-40 degrees, and it runs and idles just fine (for the most part, occasionally will have issues).

So, I come here asking for some help. I had it at what I THOUGHT was a good mechanic, but after fixing a few things he basically told me "I don't have time to mess with it." I about turned red with anger as I had him schedule me into his time, so it wasn't like I was being a pain and just showing up expecting him to take a look. Nevermind all that though, it doesn't really concern the issues I am having with the truck.

Any advice/insight? It has a new fuel filter also. Thanks in advance for any/all help, I greatly appreciate it.

 

Did you spray it and work it a few times. And you can also give a little shot of wd40 when your done.
After doing it you need to disconnect the battery for about 5 min and then the computer will relearn with the clean IAC on there.
After you install the new one. Reset the computer and see if it doesn't straighten out after a little wile of driving.

 

I had the battery disconnected throughout the whole process, and we did work it up and down quite a bit after spraying it. We did not, however, spray some WD-40 in there while working it. Either way, I am going to buy a new one so that it rules out the IAC.

I went out and scanned the new codes this evening. I am throwing a P0171 Bank 1 Lean and a P0174 Bank 2 Lean. At least the EGR hoses cleared the EGR code. Still stumped with the lean codes, though. Tomorrow I will pick up a new IAC and install it to see what happens. Hopefully that will be the cure.

 

A lot of times a lean code will be caused by a vacuum leak.
Check all your vacuum lines.

 

All the lines have been checked and double checked. I am starting to wonder about an intake manifold leak though...

 

Make sure you check pcv vacuum lines. Thats what turned out to be my problem. It was leaking where it plugs in the back of the throttle body.

 

All the vacuum lines are intact and in good working order.

I do notice that I have one or two exhaust clamps (after cat) that rattle when I put the truck in gear. I don't see how this would affect my lean codes, but I will try to tighten them down and see what happens.

As of right now, the temperature has been above 30 for the past couple of days. I have not had a problem with the truck dieing, idling rough, or the sorts. WHY on earth would this ONLY happen when the temperature is below freezing?! Makes absolutely no sense to me...

 

Check and test the MAF and IAT sensors in the air duct. either or both, dirty or having wire issues can cause the idle to vary when cold. The lean codes can mean a lot of things. You really need to hook up a vac gauge to start with. Steady 17-19" is good. Wavering or floating needle will tell you a lot. In that case, almost certainly a vac leak. Steady normal reading, look for loose duct work joints, especially hoses to the IAC. With age, they fit a little loose. You may have had an icing problem, within the IAC, or other.

Dave