Hello,

Tried searching but it only brought up a bunch of other unrelated stuff...

The engine has been shuddering in the 1200-1800 range when just barely under load. When coasting it's fine, when pressing on the gas slightly, it's fine (even with no increase in rpm's...just a light press on the pedal). It only happens when it's in that range where it's neither propelling the truck forward nor coasting against the engine that it happens.

Anyway, this happened about three years ago and the problem turned out to be a bad DFPE sensor. I replaced it (along w/ both hoses) and that fixed the problem.

It has just recently started doing it again (about two months ago) and it thew the "EGR Insufficient" code...same as last time. So, I replaced the DFPE again and cleared the code, but the problem still exists and the same code returned. I'm not overly familiar with the EGR system so I'm looking for advice on what to check next. Valve, etc...

Thanks in advance.

 

Check the vacuum lines running to the dpfe sensor all the way back to the manifold for leaks. I had a broken line and it came up with the low egr flow fault.

 

You mean the lines running from the sensor down to the exaust manifold? They're both new...replaced with the sensor.

 

Actually it is the lines that run to the egr itself (sorry about the confusion). The line runs from the egr to a christmas tree sort of connectors and from there goes on to the manifold. Trace these lines back and see what you find. Mine were damaged behind the alternator. The lack of vacuum was causing the sensor to give the low egr flow fault.

 

Gotchya. I'll check those when it warms up a little. It's been down around zero degrees lately...

 

OK,

Finally got a chance to check things out. Here's what I found:

With 5-in vac to the EGR valve at idle, the engine wants to stall. Valve seems OK...unless anyone knows why it may still not be.

The valve control solenoid was full of crud and its coil tested iffy. I replaced that. It seemed to improve slightly, but still gives the code.

Vac lines are all properly sealed and I have plenty of vac pressure to the solenoid.

Even though the DFPE sensor is fairly new (and newer style), I checked at the terminals for proper voltage and all checks out.

So...any other ideas??

Thanks in advance.

 

Have you pulled off the EGR valve and inspected the passageways underneath for clogging?

 

I thought about doing that, but after it appeared to be function properly when I manually applied vac pressure, I didn't.

So...if the ports or the valve itself were clogged, the vac test would have failed...am I right about that?

At current, I have a newer DFPE, brand new vac regulator solenoid, and a (what appears to be) a functioning EGR valve.

What next? I will still check the ports when I get a chance...but I'm not holding my breath.

 

Yes, if they were clogged. However, if they were restricted, at idle there could be sufficient flow, but not at higher RPMs.

 

Also, after each repair you do, you need to clear the codes, and then run the engine.

If you do decide to removed and clean the EGR passages, here's a post I wrote describing my experience with the job:

https://www.ford-trucks.com/forums/8...-a-5-4-2v.html

 

Here's what happened today...quite a bit.

I was going to take the EGR valve off and check/clean whatever I could get to. The big nut from the EGR tube came right off, but both bolts that hold the valve to the intake were completely seized. After much soaking and some heat, the front bolt finally got about half way out then snapped off. I left the back one alone for the moment. There was enough of the front bolt sticking out with clean threads that I was able to get a nut on it to keep the valve tight. Messing with those and getting the valve off is a project for another day.

I removed the throttle body to inspect the EGR port. Looked suprisingly clean for 150,000 miles. I stuck a small brush into the port and got about 2 1/2" in with no obstructions. That's as far as I felt safe with while the valve was still attached.

I decided to put my vac gauge in line with the valve to see what was actually going on while driving. I started in my driveway with the e-brake on and foot on the brake pedal. With it in gear, I brought the rpms up to about 1400...which is where I notice the jerking the most while driving. The gauge started at "0" and it ran great. After about 3 seconds holding 1400 rpm, the gauge jumped to about 3.5" and the engine IMMEDIATELY ran rough and sputtered. The gauge slowly climbed towards 5" and ended up a little over that...at which point the engine was running considerably worse than at 3". I pressed the release button on my gauge (effectively removing vac from the valve) and the engine IMMEDIATELY ran prefectly smooth. So, from what I gather, the system seems to be calling for additional EGR flow when it's not needed.

My first thought was a bad DFPE sensor, but that sensor is only about 3 months old...and it's the newer style. Both hoses on the DFPE are also new and clear of any blockage. The part that has me mystified is that the code is "EGR Insufficient" and not "EGR Excessive" so the computer seems to think that there's no flow at all when there is some...which it tries to fix by increasing the amount of flow...which makes things worse.

So...where do I go from here? Did I get a dud sensor? Bad EGR tube?

 

That sounds like a faulty EGR valve - mechanically it could be a broken return spring or a torn diaphram in the valve, and those things can happen if the valve bore and seat are caked up with carbon and/or it once was caked up enough that the valve became stuck enough that it broke one or the other of those things and now the valve is just flopping around in there. .... and aside from the vacuum test, the only way you're gonna know the physical condition of that valve is to remove it, like when you had the TB off the intake. I replaced my EGR when I took it off and saw it was physically 'welded' shut with carbon.

 

I know that it's opening and closing because it passes the vac test as far as I know. Maybe it's opening too far for the amount of vac pressure it's getting? I'm going to replace the valve anyway (already have one) since I have to go to all the trouble to get the old one off there (probably have to drill out/re-tap for the bolts). I'll give the ports a good cleaning while I've got things apart.

The thing that still has me mystified is that the system keeps calling for more EGR when it already has too much (and doesn't need it)...while it was running rough, I took vac away from the valve and it ran perfectly so there's still something up there...

 

Has the EGR ever been replaced on the vehicle or serviced by someone else (dealer, etc), ie are you the original owner? Reason I ask is that the torque value for those bolts is not high enough to cause them to be that stuck, I'm wondering if someone overtorqued them at some point. .... or worse yet, stripped the threads. Mine came off pretty easy, and I replaced the bolts (using antisieze on the threads) using the correct torque. Just sounds strange that your bolts are on so tight...

 

I think you either have a vacuum leak in the line supplying vacuum to the EGR valve, or, as vze2sgxa mentioned, a torn diaphram inside the EGR valve. When the solenoid applies vacuum to the EGR valve/diaphram, that opens up a vacuum leak in the line or diaphram and the engine runs ragged. There is insufficient vacuum to open the EGR valve and the PCM interprets that as insufficient EGR flow.
When you take the vacuum away there is no more vacuum leak and the engine runs fine except the EGR is closed and will prolly set the Insufficient EGR flow code.