Insufficient EGR flow code

[ahodges]

I have a 96 4.0 OHV Explorer with 123k on it. 30k on this engine.

Here's the story. The Check Engine light came on about 6 months ago for this Insufficient EGR flow code, I don't know what the code number is right now but if someone would find that helpful I can post it up later.

So anyhow, I've replace the DPFE sensor, the solenoid that operates the EGR valve, checked the vacuum lines, and the EGR valve itself and nothing has fixed the problem. The way I checked the EGR valve was by attaching a brake line bleeder manuel vacuum pump to it while the engine was running to see if the idle changed, it did - a lot.

I'm at a loss as to what to do next or what it can be. I runs fine besides that except for when I drive it for a while, shut it off in a parking lot, and come back to start it within a half hour or so it will barely idle. After about 10-30 seconds it straightens out and runs fine. I don't know if the 2 problems are related or not.

Any ideas would be great!

 

[2000StreetRod]

Clogged DPFE hoses?

Insufficient EGR flow: Have you tried cleaning the hoses that connect between the DPFE and the ports on the EGR tube? During certain conditions after engine start the PCM tests the EGR valve when closed and open. It uses the DPFE voltage output to confirm the EGR valve states. If the DPFE voltage is too low then the PCM assumes the EGR valve is not fully opening. The DPFE output voltage is proportional to the static pressure difference between the two ports. If the ports or the tubes connected to the ports are clogged then the output voltage will not reflect the actual flow of exhaust thru the orifice in the EGR tube. I believe once the PCM determines there is an EGR problem it disables the EGR function for the remainder of that drive cycle.

The warm start rough idle problem may be unrelated to the EGR system problem. The EGR valve should be closed when the engine is at idle and at high engine loads. Have you cleaned your IAC valve recently?

 

[ahodges]

No, I don't think I have checked the DPFE tubes. I have a Ranger too that I just replaced them so I'm begining to mix up the two, lol. I'll have to do that next to make sure they aren't clogged or collapsed. The outside of the tubes look good so I never gave it a second thought.

I haven't really cleaned the IAC valve recently.. Its been about 30k i guess. I'll take a look at that also while I'm at it!

Thanks for the reply!

 

[ahodges]

So I check the DPFE tubes and the EGR tube for blockage and found that nothing was blocking them. I took the new DPFE sensor off the explorer and put it on my ranger to see if the new sensor was bad. It isn't bad since it didn't cause the CEL to come on in the ranger... I'm stumped...

 

[Wickedgood]

Just went through the same thing with my '99 5.0. Replaced sensor, solenoid, etc.
Come to find out I had reversed the vac hoses on the DPFE. Also found the rubber hose going from the evap to intake was degraded badly. Replaced and all good now.
Finding the issue can certainly be frustrating.

 

[2000StreetRod]

Leaking diaphragm?

Maybe your EGR valve diaphragm is cracked and leaking vacuum. The PCM generates a square wave output to the EGR vacuum regulator. The amount that the EGR valve is open depends on the duty cycle of the square wave. If there is a leak in the diaphragm it may not respond fast enough to achieve the PCM commanded result. You might try hooking your manual vacuum pump to the EGR valve with the engine off to see if the diaphragm holds the vacuum.

 

[ahodges]

Thanks for the thoughts guys. I know that the DPFE is hooked up right (not backwards) and that the lines are in good shape.

How long should I wait to see if the diaphram is leaking? How much pressure should it take to make it move? It seemed to take more than I expected when I tested it the first time.

 

[2000StreetRod]

diaphragm test

EGRS exhaust gas flow O&T (cont)

 

[ragajungle]

^^^ That's some great info! Thanks! ^^^

 

[ahodges]

EGRS exhaust gas flow O&T (cont)

Thanks a lot!! Can't get any better explaination than that!