I have a 98 F150 with orp and 5.4 motor. It has around 80,00 miles on it and runs great. Just got back from a 500 mile trip and got perfect gas mileage. My problem is that it is idleing very rough and almost wants to die. Any ideas?
thanks

 

Do a search for IAC, idle air control valve. More than likely your problem.
Good luck!

 

Sticking EGR valve can cause this if it doesn't shut all the way at a idle. I got a piece of dirt (carbon) stuck in one once holding it part way open - had to remove the EGR valve and take the dirt out.
Dave

 

Where exactly is the EGR valve located. The other valve didn't fix it.

 

Remove the black plastic shroud that says 5.4 above the thottle. The IAC is a small silver cylinder with an electrical connector at one end. Two bolts hold the thing down. Save the gasket.

 

read below

 

read below

 

One more thing, well I will just tell you the whole story real quick. We pulled a 27ft boat about 250 miles to Lake of the Ozarks. Noticed the first time we filled up when we were just idleing that it was real rough but wouldn't die. Truck ran like a champ the whole time pulling boat. Got good gas mileage the whole trip. So we drop the boat off and head back still got the same rough idle but it would idle fine some of the time. Also noticed on the way back that his truck would sometimes not want to shift out of gear to go into overdrive. Really noticed it when he had the cruise on and it would kick down going up a hill and then never go back to overdrive. Also the other day he said it died on him a couple of times. The truck runs fine other than idle. We repalced the IAC and nothing changed. We reset the computer and nothing. Should we put the new IAC back in and give it a chance. Also we cleaned the MAF and throttle body. Eventually it through the CE light but my bro erased it before we could scan it. Is there anyway to check the IAC if it is functioning properly.

I just think it is weird. I have done tons of searching on the board and nothing is similar to his. I would think if it was something serious that it would get bad gas mileage and miss all the time.

I own a Toyota Tacoma and have had similar rough idles and changing the PCV fixed it. Has anyone had any problems with them on the fords. Also people with Tacomas have had problems with K&N filters and the oil on them coating the MAF sensor and ruining it. The MAF on the ford was a little dirty on the back spring. I cleaned it with some electric parts cleaner and a q-tip.

Any help would be greatly appreciated.

 

btt

 

Sounds familiar. My 98 Exp w/5.4 had a rough idle, getting progressively worse. Checked this, checked that, no good. Read some posts on the boards from folks who had found an elbow connector on the back (way in the back) of the engine had cracked. Apparently common. I checked, sure enough. It's a vacuum connection, and the "assembly" if you buy it from the dealer has two or three short hoses plus the PCV. I replaced that, idle back to normal.

 

When yours was running bad did it through a CE light.

 

Yep. Funny thing is, though, there was picture that my wife had stuck against the inst cluster plastic, so I didn't notice it for a while. But sure enough, once the idle got bad enough that I knew something had to be wrong, I started wondering why there was no CE light, then I noticed the picture covering it up. After replacing that cracked elbow and leaving the battery disconnected for 15 minutes or so, the light never came back.

You can check the elbow by reaching in around the top of the engine to the back. It seems it was pretty close to the center, up on top, relatively easy to get to. Of course, the normal caveats apply, try it without the engine running, engine cool, etc. If the leak is big enough it could actually suck something into the hose (don't ask me how I know this). I actually did a temp fix when I found it, since it was too late to get parts. I wrapped the heck out of it with electrical tape so that it would hold vacuum. Worked for a day or two until I got the correct parts to fix it.

 

OK, I've got the code reading 0171 leane bank 1&2. I have been reading articles on this code and people say its either a vacum line or pcv valve. One problem I saw right away is there are three lines coming off od the passenger side intake and I know one hose has anitfreeze in it but the middle hose goes to the passenger side valve cover. This hose at the rubber elbow is complete sqeezed shut. Would this be a cause? Also where is the pcv valve?

 

The hose that goes directly into the valve cover on the passenger side is attached to the PCV. You can just pull it out, with a little wiggling. Engine off! Brush/blow away dirt first, etc. One of the hoses off of the split from the PCV goes around the back of the engine, then connects near the rear top. That's the one that cracked on mine.

I didn't get the codes off mine, so I can't say if those are the same. Could be, since the hose is connected to the PCV.

 

Did your truck start running right immediately after you fixed or did it take awhile. Mine was cracked also and I replaced and still the same rough idle.