EG AARG

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Jun 15, 2011 | 09:03 AM

0gers

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EG AARG

2000 Expy 4.6l
I’ve been troubleshooting a low EGR flow code for a few days now. I’ve eliminated any electrical issues, and I’m pretty certain there is a mechanical problem. (I have a 98 Expy 5.4 which I can swap parts from to troubleshoot)

At idle my DPFE reads about 1.2V. If I manually open the valve (with a vacuum pump) it goes up to 1.3V. The readings are good because there is very little flow. If I completely open the valve the idle drops by maybe 100RPM. The same test on the 98 would kill the engine and read about 5V. I’ve removed the EGR valve and the tube and given them a good ole clean. The valve seems to function OK, although I’m not sure it’s opening all the way. At max stroke the piston is about ½ way up the hole (if that makes sense). It is very hard to see what is going on inside the EGR tube. I’ve thrown every chemical in my toolbox at it to try and clean it out as well as wildly jabbing bits of wire inside to try and remove any obstructions.
If I blow through the EGR tube there is a small amount of resistance. I realize there is an orifice plate inside there, so you I’d expect a little resistance, but I don’t know if this normal and is causing the low flow?

Any tips, tricks or advice? My next step is to swap out the EGR valve and tube from the 98 epxy…….. but that sounds like a lot of work if I can avoid it. Looks like a new valve is about $50 and the same for a new tube……....

Jun 15, 2011 | 11:43 AM

pdqford

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From: Central NYS

Quote:

Originally Posted by 0gers

If I completely open the valve the idle drops by maybe 100RPM.

It should drop further than that, or stall.

Quote:

Originally Posted by 0gers

If I blow through the EGR tube there is a small amount of resistance. I realize there is an orifice plate inside there, so you I’d expect a little resistance, but I don’t know if this normal and is causing the low flow?

Although the DPFE's are known to go bad, I'd first check to see if there is any restriction on the outlet side of the EGR toward the intake manifold. That is where they typically load up with carbon.

(Is this a high mileage vehicle and/or using oil?)

Jun 15, 2011 | 02:23 PM

0gers

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The truck has about 140k on it and it uses about 1 quart of oil every 2000 miles.

The EGR to the intake hole is clear of any obstruction.

I have a good DPFE on my other expy and I've switched them over. I'm 99% certain it's not an electrical problem.

Jun 15, 2011 | 05:08 PM

pdqford

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From: Central NYS

Quote:

Originally Posted by 0gers

The EGR to the intake hole is clear of any obstruction.

Understood. The hole may be clear, but the passage ways through the intake must be clear, also. Any blockage any where in the system will minimize the differential pressure upstream vs down stream of the orifice.

Is there any resistance when you try to blow air into the hole to the intake manifold?

When you open the EGR valve at idle the engine should come close to dying.

How does the 5.4 run with the 4.6's DPFE?

And how does the 4.6 run with the 5.4's DPFE?

Jun 15, 2011 | 10:01 PM

0gers

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Thanks PDQ Ford

I haven't blown into the EGR/intake passageway, but I did push a 3 inch long 3/8 extension into the hole. It seemed clear. It seemed like there was just a straight hole into the throttle body.

After swaping the DPFE's over I never switched them back. The 5.4 has been running good with the 4.6DPFE for a few hundred miles now. The 4.6 throws the same error code with either DPFE.

I also replaced both the hoses from the EGR tube to the DPFE, swapped over the vacuum solenoid from the 5.4 and checked the condition of all the wires and vacuum lines, this is why I say I'm 99% certain the problem is some sort of mechanical blockage.

I took another look tonight, and the EGR tube and valve from the 5.4 arent interchangeable with the 4.6

If I connect my mityvac pump to the 5.4 EGR valve it takes about 3 pumps to stall the engine. On the 4.6 the mityvac & EGR hold the vacuum, but after pumping as much vacuum as possible the engine barely misses a beat.

Jun 15, 2011 | 10:50 PM

pdqford

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From: Central NYS

Quote:

Originally Posted by 0gers

That sure sounds like a blockage in the EGR passages. I'm assuming you had the 4.6's EGR valve off and verified that both ports are open? And that the pintle moves when vacuum is applied to the diaphram?

Are you getting any other codes besides the P0401?

We can verify that the wiring from the DPFE to the PCM is not causing the problem by hooking your mighty mite to the smaller hose coming off the DPFE and checking the DPFE voltage with KOEO. It should be between .25v and 1.25v.

Then apply vacuum to the smaller hose and the DPFE voltage should rise to at least 4.0v.

If it rises to the 4.0v range, that shows that the DPFE is reacting correctly, and the 1.3 volts you got with vacuum applied to the EGR valve in post #1 indicates there is not enough flow to peg the DPFE.

Might try putting a hose into the EGR/intake port and see if you can blow air into the EGR passage way. Basically, the intake has to "suck" the exhaust gasses past that orifice in the EGR tube to great the differential pressure that the DPFE measures.

Good luck . . .

Jun 17, 2011 | 10:47 AM

0gers

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YAY! It's fixed.

Thanks for the help.

I removed the throttle body and part of the intake last night and the EGR passages were completely blocked. I did not realize that there were 2 ancilliary holes which could get blocked. You can't see them from above. It looks like the main passage goes straight into the intake manifold but it doesn't.

Just in case somebody has a similar problem one day, here are some photo's from underneath of the offending passages.

https://picasaweb.google.com/1018131...J6m5MLnyLO-4wE#