Bad EGR?

Hey guys,

I was wondering what the symtoms are of a bad EGR valve or sensor (whatever it is lol)

I've been experiencing some hesitation while accelorating in mid speeds, and tonight it was at idle at a stop light and the RPM's started bouncing from 500 to about 1100 over and over, it did this for a few seconds and then stopped. It hasnt done it since but i know that what it did is NOT normal.

If the EGR is the issue, is this a cheap part? easy to install? Please post some good news, i need it after the week i've had!:shootout:

My EGR sensor went, which is common since its aluminum. Thats a 75 dollar part or something. I can't remember if your 4.6 or 5.4, but 4.6s have the tendency to let the EGR port holes in the throttle body gum up with carbon. I never noticed any variation in rpms ever really. I only started pulling codes. Although I suppose that if the sensor is giving fault readings it can cause the valve to open at inappropriate times and cause some hessitation.

I'd start by doing;
1) get a vacume pump and connect it to the EGR by removing the vacume line on top and build up a vacume using that. It should cause the truck to run rough, or possibly stall. I could never get my 4.6 to stall, no matter how quick I'd do it. It would get right to the point of stalling, then correct it and come back to a rough idle. If it that works, and it doesn't seem to come back and forth from smooth and rough idle I'd say the valve is good.

2) If you have the aluminum DPFE sensor replace it, its going to go anyways and the new ones are plastic.
Try and drive it see what happens.

3) For perfection I bought new gaskets for the entire throttle body and took it off and cleaned it up. Wasn't that hard, took about 2-3 hours for the first time and I was taking my time. Found quite a bit of gunk in the holes. They say you can use some kind of cleaner to clean it while running but it hurts the cats.

I ended up replacing my entire EGR system since I got headers and the old tube was all rusted and shit.

Ok, this is going to sound funny, but can someone take a pic of the engine and show me where this EGR sensor is? My truck is a 5.4 Avro, and what do you mean a vacume pump?

That's just the thing.....About the rough idle. When it's parked it idles extremely smooth. so a rough idle is not a problem at all.

The rough idle should be only when you activate the EGR with the vacume pump. The pump is like a little hand pump that almost looks like those hand grip workout things with a fitting on the end. It creates a vacume instead of compressing air. Thats how the EGR valve is controlled.

First take off the Triton plastic cover over the throttle body.

http://www.fordf150.net/photos/data/500/3736EGR.JPG

See that little round disc thing with the fitting on top, thats the EGR valve. The large metal tube on it goes down to the exhaust manifolds.

http://www.f150online.com/galleries/images/3376-4889-92125.jpg

Thats the EGR sensor, or specifically, the DPFE sensor. The two hoses underneath the sensor go to the EGR tube. See hows it aluminum, it corrodes inside. The new ones are plastic.

If you put the vacume pump on the EGR valve (the fitting on top of the disk, remove the other vacume hose) and apply vacume it'll open the valve and allow exhaust gases into the intake. That'll make the engine run rough or possibly stall. If that happens the valve is good. Make sure it closes also when you relieve the vacume and idle smooths out. This won't have anything to do with your normal idle because it only functions when certian nitrogen oxides are detected which is in high temperature combustion.

IF this has anything to do with the EGR system this is likely to clear it up. The only other problem I've heard of was the tube clogging although I thinks thats the more extreme of situations.

Remember, this is your exhaust we're talking about which is old and possibly rusty. If you remove the EGR you might move the tube to the point where it doesn't seal as well and you might get a small leak. I installed headers and a brand new EGR valve and a new tube so mine was sealed nicely but I had the old rusty tube on for a while and you could hear it under pressure.

By the way forget the throttle body part since your 5.4. Although you could still do it.

That second photo link didnt work? Thanks for all the detailed help Avro. It's much appreciated.

Do you have any idea about the RPM's bouncing like they did?

It seems to work for me. Try searching DPFE on google pics.

RPMs bouncing? Hmmm, is it consistent in every gear or just one?

If you want just detach the vacume line from the EGR to cut it out and see if the bouncing persists.

No it only bounced once and it was at idle while sitting at a stop light. did it for about 10 seconds and stopped. It hasnt done it again since that one time, but something was obviously wrong with it for it to do that.....so i want to try and catch whatever is wrong fast before it makes other things go bad lol

It could also be your IAC. It is a little valve that allows air to bypass the throttle body so the computer can regulate the idle speed. These are notorious for getting gunked up or just plain wearing out.

Matt R