2.5L ('98-'01) P0442 rough idle and stalling. Everything checks out.

[ben_2_go]

I just redid my DPFE sensor and wiring along with EGR valve and tubes. It was running great with no issues at all and no codes. Coming home from dinner a few nights ago, it stalled while sitting at a red light. Restarted, but had to keep my foot on the throttle or it would die. By the time I got home, it was idling but erratic. Scanned the PCM and got code P0442. I know this is usually a fuel cap issue but that wouldn't cause running problems. The IAC vlave isn't very old. That could be the issue. The purge valve and charcoal canster valves have never been changed. I hate to throw parts at it, but I may change all three parts because their age, and the IAC valve was a cheapo Chinisum part. Anyone have any other ideas before I start buying parts?

 

[franklin2]

What did you just mess with? The EGR system. I think I would look there. A chunk of carbon can get stuck in the valve and hold it open, making a very large vacuum leak to the engine. If the EGR hasn't functioned in a long time, now that it is working it might have dislodge some debris in the pipe and stuck the valve open.

You can test this theory by making a block off gasket out of a aluminum pop can and slip it under the EGR to block it off.

 

[ben_2_go]

What did you just mess with? The EGR system. I think I would look there. A chunk of carbon can get stuck in the valve and hold it open, making a very large vacuum leak to the engine. If the EGR hasn't functioned in a long time, now that it is working it might have dislodge some debris in the pipe and stuck the valve open.

You can test this theory by making a block off gasket out of a aluminum pop can and slip it under the EGR to block it off.

The entire system was changed as far as the EGR and all the tubes and lines goes. I cleaned out the manifold port. There wasn't any thing in there except fine soot. That was done several weeks ago maybe over a month now.

 

[ben_2_go]

My issue with this was the IAC and the purge valve. They were both acting up. Not 100% which was causing the P0442 code. Since making repairs, idle is stable.

 

[ben_2_go]

Well P0442 came back. Not the fuel cap or any other things I can find on forums. Was in the shop yesterday. They could find nothing wrong either. Smoke test showed no vacuum leaks small or big. I have a bit of an unsteady idle but it's only barely noticeable. Most don't even know it and I had to use a scan tool to watch rpm to actually back up my line of thinking. I went over all of the vacuum lines and connections just to be sure. It hasn't been long ago I went through and replaced a lot of the little rubber fittings and a few of the plastic lines. Rechecked my work and nothing is a miss there.

 

[-Nate]

Silly question : have you yet removed and cleaned Hospital Clean the Idle Air Control Valve ? .

That made a HUGE improvement on my 2.4L 4 bagner .

 

[ben_2_go]

Silly question : have you yet removed and cleaned Hospital Clean the Idle Air Control Valve ? .

That made a HUGE improvement on my 2.4L 4 bagner .

Replace it 300 miles ago with a brand new Standard Motor products unit from Rock auto. Almost everything on my engine has been replaced over the last 1000 miles that is electrical. I even replaced the connectors on everything. What sucks is that I was an ASE certified auto tech back in the 90s and early 2000s when this thing was made and it's beat my ass for the last 20 years I've owned it. I hate Ford.

 

[-Nate]

Okay, thanx for the update .

FWIW, I have heard that only Ford and T (I forget the full name) branded IAV's are any good .

I'm a Bowtie Guy my entire life but stumbled across my '01 Danger Ranger (what my racer son calls it) by chance and I'm very impressed by it .

 

[Blmpkn]

FWIW, I have heard that only Ford and T (I forget the full name) branded IAV's are any good .

Oooh.. yes. Every so often I come across a post that has @Ron D Explaining why the Motorcraft style IAC's are the only ones that really work.. something about a stepper motor lol..

 

[-Nate]

The modern intake air bypass valves are electric stepper motors and need to *instantly* make minute changes accurately .

If you had a fuel injected vehicle in the late 1960's ~ mid 1980's and it was imported it probably had a thermally controlled intake air by pass valve that had a bimetallic coil spring and electric heating element, these were why those had such high idle speeds on really cold mornings .

Simple and effective -but- those also routed the intake air idle control air from the crank case, sort of a variable PCV valve and they'd get all gunked up and cause all manner of wonky idle problems, most often "hunting" where you'd pull up to a stop and the engine would rev. up then nearly die before over fueling a moment and revving up again....

This was really aggravating as no shop nor the dealer wanted the Mechanics to $pend the time to clean the A.I.V. before it was a problem .

I've been busy (or, lazy, you choose) so I've not yet addressed this on my 2.5L Ranger's idle issue ~ after I cleaned the snot out of the I.A.V. it idles slightly slower and I like this as it goes into first gear easier and smoother at traffic lights .

I'm pretty sure the insistence on a MotoCraft part (or the "T" one) is simply an initial quality control thing ~ I used to sell Standard / Highgrade / Jiffy parts in the early 1970's any they looked neat but were pretty low quality, coils, contact points and condensers often failed in short order .

I want to waft some Ether (starting fluid, when used cautiously if's a fantastic diagnosis / cleaning tool) over the engine to see if it effects the hot idle speed .

My engine gets washed at least once a year so it's easier to work on and less troublesome in general .

 

[ben_2_go]

Replaced the generic IAC valve today with a T Series that has been recommended since I couldn't get the Motorcraft part. Now when I start the truck, the idle hangs between 2000 and 2500 rpm for about 10 seconds before coming back down to a high idle of 900-1000 rpm. I drove the truck to make sure everything was working and the rpm will occasionally hang at 2000-2500 rpm and almost caused me to run a stop sign and end up in a house. Now I have the code P1506 which is the code for the IAC valve. I may try to clean the old one and reinstall it. I also rechecked for vacuum leaks and found none. Smoke test revealed nothing.

 

[franklin2]

With the engine fully warmed up and idling as good as you can get it, unplug the idle air control valve while the engine is running. It should slow way down and almost stall out. Or run very slowly. If it keeps running right along at 1000rpm, and you do not have any vacuum leaks, someone may have previously messed with the idle stop screw. You can mark this screw where it is, and then turn it back till the engine is barely idling. Then plug the idle air control valve back in and run it for a few days so the computer can relearn the idle.

 

[ben_2_go]

With the engine fully warmed up and idling as good as you can get it, unplug the idle air control valve while the engine is running. It should slow way down and almost stall out. Or run very slowly. If it keeps running right along at 1000rpm, and you do not have any vacuum leaks, someone may have previously messed with the idle stop screw. You can mark this screw where it is, and then turn it back till the engine is barely idling. Then plug the idle air control valve back in and run it for a few days so the computer can relearn the idle.

I will try that, thanks.

 

[ben_2_go]

I'm second owner of this truck. I bought it in 2003 with 50,000 miles on it. I didn't expect anyone had screwed with the throttle stop screw. Everything check out so I pulled the IAC valve. I looked inside and the plunger, for the lack of a better term, was wide open. I went and dug out my old Ford IAC I replaced years ago. It was barely open. I cleaned it best I could with throttle body cleaner and made sure to keep it up right so nothing got into the electrical solenoid. I reinstalled it with a new expensive gasket. I no longer have the issue with high idle, and the idle hanging while coasting. Now I have the same problem I had when I originally replaced the IAC the first time. It won't idle high enough and lopes like a cammed V8. It also shuts down when coming to a stop after driving for a while. I guess I am going to have to find another Ford/Motorcraft IAC. It really pisses me off that I spent around $70 on a new IAC that doesn't work.

 

[-Nate]

Ben ;

Consider using the manual idle stop screw to raise up the idle .

I finally got the time to use spray Ether (starting fluid) all around over and under the intake manifold, IAC and so on with the engine idling hot with the A/C on, no change whatsoever so now I guess I too will be looking for the 'T' branded IAC valve,....