EGR issue

[Earl43P]

2000 2.5 (all stock), new to me truck, had it about a month, >1000 miles.

Did all the routine stuff, cleaned the IAC and TB, found and fixed a broken vacuum line, etc. Replaced the DPFE because it ran "skippy" at light throttle and had a code (P0401). PO had run it "for years" with that CEL light and would occasionally reset the code (his BIL is a Ford Tech).

Reset PCM with Scangage II, been driving it all over, even two highway trips over 400 miles each, plus returns. Getting about 340-380 miles per tank (19.5 gal tank), has good acceleration.

Still runs skippy at light throttle, any gear. Not a misfire.

So, I pulled the vacuum elbow off the EGR valve itself, so it cannot open, plugged the open line. Runs like butter. Couldn't be any smoother.

So, I know it's EGR. I've had some dealings with Ford EGRs over the years and have been all over the Tomco site with their Tech Tips and voltage readings, tests, etc. I can even watch the EGR readings on the ScanGage II in real time and it looks like normal operation, but obviously is not. I also looked at the O2 sensor and it responds quite quickly and looks good too.

The CEL hasn't come on from unplugging the valve yet. I expect it to set a code once I get some steady speeds for longer distances. My commute is 4 miles, so it may be a few days. Irrelevant anyway.

When I replaced the DPFE, the original was pot metal, so I assume factory installed. The new one is plastic.


So, I guess I'm asking if anybody can give me a clue what the long term effect of having a bad DPFE might be. Could this thing be all carboned up?

I'll likely pull the EGR valve away from the intake over the weekend and clean that area up, but I'm looking for any insight. The silicon tubing to the DPFE needed the ends trimmed from being stuck to the old aluminum DPFE, but otherwise looked good, no cracks. I guess I'll push something through those, make sure they aren't blocked.

I'm also going to look hard at the TPS because the Scangage II reports it at 18 when TB is fully closed. My old 2000 truck was at 16. Thinking maybe the PCM is seeing too high of a TPS setting and dialing up more EGR opening than needed at light throttle. I'll do a full reset and idle relearn if I do any TPS tweeks.

Not too much to that system, a control solenoid valve, an EGR valve and the DPFE and its hoses. Sorry for being so wordy. It may be a while till I get back to my own thread so I wanted to be thorough. Miller time!

Have a great weekend! I'll be installing a new countertop, trimming shrubs, and tinkering with this truck and swimming.

 

[Earl43P]

Update:

Been driving it around town, running nicely with the EGR valve vacuum line removed and plugged. The weird part is that the ScangageII still shows DPFE changing values anytime I drive. I'm sure I don't have the signal and reference hoses mixed up. Can't see how the DPFE can be sending varying values if the EGR valve can't open.

Bears further investigation.

 

[v8318cid]

Exhaust pressure may be pushing the valve off it's seat during normal driving, in which case the sensor would still pick up on it. The vacuum may only be an "assist" or for when the ECU thinks it would help emissions. Not sure. Anyone second (or correct) that?

 

[Earl43P]

Interesting.

I'd think restricted exhaust could especially have that effect.
Seen it on a Chrysler product, blocked cat blew the EGR sensor hose.

Thanks for your input.

 

[Earl43P]

It finally set the P0401 code this morning. Took about 30 miles.

Unrelated, I found a caliper bolt that was too long, causing the LF to judder and grab. It was bottoming out in the spindle (blind) hole.

For the record, front brake caliper bracket bolts are M12-1.75 35mm length.
Dorman/HELP part #13898 and they come with Loc-Tite pre-applied. $6/pair.