My truck idles rough. I just hit 80k miles and this is the only problem I've ever had except for the motor pulling bracket being broken in half and rubbing/making a chatter. It isn't undrivable or anything. The CEL isn't on and has never been on. If it wasn't for someone pointing it out to me I might have never noticed aside from the vibration when I am in O/D and driving under 1500 rpm.

This started 8-12 months ago.

Symptoms:

1) Rough idle. AC on or off, in gear, neutral, and park. I can see the RPMs drop by 50 and then catch back up. It is plainly felt and heard.

2) Miss up to about 1500rpm. It is worse on this hill I drive up on way to work every day. The truck gets into OD 45/50 mph and going up the hill slows the truck a little so when I apply a little gas it vibrates the truck quite a bit. If I give it more gas then it drops down and moves fine. If I don't drop down below 1500rpm on the hill, everything is fine. It is not gear dependent though, just more likely to sustain >1500rpm in OD than other gears I guess.

3) Gas mileage? Not sure, I never keep track to be honest. A couple years ago I took a transfer and I only drive about 3-4 miles to work.

Here is what I've done so far:

6 months ago: New NGK sparkplugs.
4 months ago: Clean MAF and intake.
1 week ago : Spark plug wires/reset ECU
Yesterday : Clean EGR/Add injector cleaner to tank.(Berryman B12)

It occurred to me a few weeks ago that I had a wireless OBD2 adapter for my phone. I already had the wires, so I went ahead and changed them. I reset the computer(disconnect battery/turn headlights on) and I've put about 60 miles on it since then. Nothing changed in any way.

I use the scan tool and it comes up with 1 code.

U1905 - Network

Digging a little bit deeper into the test results the only thing I see that says fail is "EGR Monitor Bank 2 fail". That is why I cleaned the EGR valve. It wasn't very dirty. I reset it when I did the plugs, but the EGR had a fail beside it then. The misfire sensors read not complete but it wasn't a fail before I reset it.

Aside from cleaning it, I unplugged it while it was running. No change. I pulled the vacuum hose while it was running and got no change (aside from a momentary idle change before I got my fingers over the vacuum hose) I assume the little electrical connector is the

It feels like it has plenty of vacuum to me and Torque reads it as being about 20-21 vacuum. I've been driving with the app open on my dash and it appears to be acting normal if the vacuum numbers are to be trusted.

I figured I had a extra can of carb cleaner, so I started the truck and sprayed all over the place on the intake. If I bent the little sprayer end and sprayed it directly down behind the intake manifold it would rev to about 820 after a couple second spray but it could just be my imagination. I used a mirror to look back there but I don't see anything amiss. In neutral with the AC off it idles between 750-800.

My path appears to be to randomly change parts and see if it fixes it or maybe remove the intake and look and see if something is dry rotted or needs fixed behind there?

I could go get a vacuum pump, take the EGR back off, and check it again. I just cleaned it, I never tried to vacuum it. I assume that it would have a low air flow/blocked air flow code if that were the problem though?

EGRs are fairly expensive, I'd rather not buy expensive electrical parts randomly.

Does anyone have any input as to what my next move should be?

 

id change those plugs to motorcraft SP-504 and get motorcraft wires as well. Have you changed the fuel filter?

 

Might want to take a good look at the coil pack too.

That's a bit concerning. How many miles are on this engine? It may be time for new plenum gaskets and isolator bolts, you have a vacuum leak back there somewhere.

 

I changed the fuel filter last month. I forgot to write that down.

I double checked the brand of plugs and I got autolite - not NGK (that was a motorcycle). Since there is no condition change before and after the plugs/wires, I think I can safely rule that out as the cause of the already existing condition. The plugs only have a few thousand miles on them at this point.

Thanks.

 

If you search, you'll find a lot of people have issues when using autolites in these trucks (or anything except motorcraft for that matter). Lots of complaints about misfires and just not running good that end up going away when they switch to motorcraft.

I wouldn't rule out the plugs just yet.

 

I just hit 80k miles. It doesn't look too bad to do by looking at it. I am going to have to get some more carb cleaner and really go at it while recording RPM and the like.

 

I will probably try this first.

 

Carb cleaner will eat rubber parts such as vacuum hoses, so the safest thing to use is propane (not lit, of course).

 

Alright. I'll see about putting a hose on the end of my propane torch and run it down behind it for a bit. It seemed to me that the carb cleaner might have actually been pooling somewhere and finally getting sucked in if the whole rpm change wasn't my imagination or the engine compensating for the miss.

 

Go with Motorcraft plugs, wires, and pack.

Although, the pack and wires still should be OK. They are made much better than they were several years ago with the silicone compounds they use now.

Stay away from the Autolights, NGKs, and Champions in the 4.2l V6.

 

I used a long length of tubing and hooked it to my propane torch. I ran it in all around the intake and got no change in RPMs. I sat for about an hour listening to it. It idles ok for a little bit and then jumps and shakes before seeming to catch back up and then run ok for a few seconds. It doesn't have the same change each time. It have about 175 RPM swing. It drops down to 650 and then catches up and moves back to 750ish. Sometimes it goes to 825 (one in 10-15 times?).

Unplugging the DPFE electrical or the EGR vacuum makes no difference. I generally checked vacuum hoses and all around the engine. I got it to throw 3 codes P0106, P0108, and P0406. This seems right given I was pulling air hoses off, so I don't think it changes anything.

I found a truck like mine but with the 5.4, same year, color, interior color, and all at the u-pull-it yard locally. I am going to go get some dash parts because I want to try my hand at a tablet dash(I'm digging torque and would like it to run all the time in dash) Will the EGR valve be the same?

 

Nope.

 

It seems unlikely that the truck would run exactly the same before and after a plug change if the plugs were the problem. Not that it isn't possibly, just unlikely. I've certainly seen stranger things. I spend a lot of time working a VW New Beetle.

 

I went to the junkyard today to see if I could get a EGR valve to just do a swap test. No luck. I ended up testing the vacuum at the EGR. I came up with over 20 just like the torque app shows. It didn't appear to change as the engine missed or anything. I've got a coil pack showing up tomorrow and I'll give that a try.

The miss isn't constant but it might be rhythmic. It levels out and then it stumbles in maybe 30 second cycles? It seems like if it was a vacuum issue associated with the EGR that it would stop/change when I plugged off the EGR.

I'm questioning whether the torque app is reporting accurately in regards to the EGR. It has the same result for the EGR in 4-5 different places and it passes in all but one. Does anyone know what it should measure in the torque app or anyone with a 4.2 that can maybe post their EGR related values in the app?

 

I had a similar issue on my sons escape. Was a bad coil.
Is yours worse in damp or wet weather?