EGR SNAFU

Ranger1 · **Joined:** Mon Oct 17, 2005 7:40 pm **Posts:** 1137

Ok, since experiencing more trouble calls than I want to recall on my CRD, and feeling that DC isn't losing any sleep on figuring out why our EGR valves are failing, I decided to revisit what could be done if the EGR valve goes belly up after warranty. Drastic issues, drastic measures :-)

Since my turbo decided to blow 2 quarts of oil into my intercooler and intake system, I decided to see how to eliminate the EGR soot from the equation if possible.

Others have tried putting a blocking plate on the exit port of the EGR valve, only to find that a CEL/MIL code was their reward for their efforts. So I made some observations, as well as burning the midnight oil on the Bosch EDC-16 control system. To cover briefly what we already know about the CRD egr and related air control/anti-shudder valve operation, I'll list it briefly as I understand it:

Normal operation of the EGR valve:
cold engine - EGR valve off, to prevent rough idle and troublesome starting
Normal temperature engine, vehicle moving - EGR valve on, unless WOT
Normal temperature engine, idle more than 60 seconds - EGR off, to ensure smooth idle and other problems with excessive soot buildup. This EGR idle parameter is also listed in the FSM.

PCM commands EGR valve on, also commands Air Control Valve to close quite a bit, reducing fresh air draw from intercooler/airbox and increasing draw from EGR valve - at this same point in time, PCM also commands Turbo vanes to minimum output, to further reduce fresh air input, at least at idle. This coordinated set of PCM commands - open egr, shut turbo output to minimum, close air control valve to nearly closed, is all to increase the draw from the intake to the egr valve, in order to ensure an adequate amount of exhaust gas will be drawn into the engine. There are probably other limit controls which are not known to us as well.

PCM further checks for rationality of EGR behavior by checking the Mass Airflow rate in the intake air box when the EGR valve is commanded open, the air control valve is nearly closed, and the turbo vanes are set for minimum flow - under these conditions, the fresh air flow rate reduces greatly, as shown by a simple test of observation. I have read that when the EGR valve is open, the fresh air rate needs to reduce at least 25% - it may be even more than this. At any rate, this reduction in fresh air intake will serve as a backup inferred value to let the PCM logic be assured that something didn't block the EGR valve from doing its job.

Observed behavior:

Hot idle in driveway, after 20 mile trip home, during turbo cooldown time, 60 - 80 seconds, EGR valve shuts, exhaust flow increases dramatically, engine exhaust note becomes quieter, at least on an Aero-Tubine muffler equipped CRD. Exhaust temperature increases noticeable for a moment, then drops.

Disconnecting both Intercooler hoses at the Intercooler when at hot idle reinforces the operation and interaction of the EGR, Air Control Valve and turbo reduction. When at hot idle, air from turbo is minimum, on other intercooler hose to intake, suction is also minimum. When the 60 -80 second period is up, the turbo output hose increases air flow dramatically and the vacuum on the other intercooler hose also increases dramatically, indicating that the air control valve has opened fully, drawing more fresh air in.

So, if one had an inoperative EGR valve, could the system be disabled without setting a CEL? Suppose a blocking plate were installed on the output port of the EGR valve, but, in addition, the other end of the EGR pipe to the intake were disconnected. In the port on the intake tube, one would connect a small air filter. So then, one could postulate that when the PCM commands the EGR valve to open, the turbo to go to minimum output, and the air control valve to close nearly shut, this time, the closing action of the air control valve would increase fresh air intake into the engine from the former egr intake port, now connected to the small air filter. The EGR valve would either remain stuck open, closed or inoperative, but the blocking plate would stop bad things from happening. Also, the closing of the air control valve would dramatically reduce the fresh air flow through the air box, and the Mass Airflow sensor would dutifully report the lower amount of air flow. There would be order in the universe of the PCM. All would be well.

Once could assume, this would eliminate the seemingly unfixable egr valve problem and stop the CEL/MIL light. Unless the EGR valve has some complex flow measuring rate indicator built in. A real flow rate indicator, not just a position indicator. Judging from the apparent quality of this part, I suspect not. Too low a price point spec I would think. I think economics may work in our favor here, a quick Mass Air flow rate check is too tempting to budget conscious constrained engineering managers. I hope this worked in our favor.

Just a thought should DC not come up with an expensive fix until we're all out of warranty. Or expect us to keep replacing EGR valves ad infinitum...

RFCRD · **Posted:** Sun Jul 16, 2006 6:25 pm

Ranger1 wrote:

PCM further checks for rationality of EGR behavior by checking the Mass Airflow rate in the intake air box when the EGR valve is commanded open, the air control valve is nearly closed, and the turbo vanes are set for minimum flow - under these conditions, the fresh air flow rate reduces greatly, as shown by a simple test of observation. I have read that when the EGR valve is open, the fresh air rate needs to reduce at least 25% - it may be even more than this. At any rate, this reduction in fresh air intake will serve as a backup inferred value to let the PCM logic be assured that something didn't block the EGR valve from doing its job.

So, if one had an inoperative EGR valve, could the system be disabled without setting a CEL? Suppose a blocking plate were installed on the output port of the EGR valve, but, in addition, the other end of the EGR pipe to the intake were disconnected. In the port on the intake tube, one would connect a small air filter. So then, one could postulate that when the PCM commands the EGR valve to open, the turbo to go to minimum output, and the air control valve to close nearly shut, this time, the closing action of the air control valve would increase fresh air intake into the engine from the former egr intake port, now connected to the small air filter. The EGR valve would either remain stuck open, closed or inoperative, but the blocking plate would stop bad things from happening. Also, the closing of the air control valve would dramatically reduce the fresh air flow through the air box, and the Mass Airflow sensor would dutifully report the lower amount of air flow. There would be order in the universe of the PCM. All would be well.

One thing I have wondered about this set-up: Would it work to plate over just the EGR port on the turbo. Then plumb filter fresh air or even hot charged air through the remaining EGR valve plumbing? Some of these systems have a temp probe in the EGR tube but I can't locate anything like that on this engine.

Ranger1 · **Joined:** Mon Oct 17, 2005 7:40 pm **Posts:** 1137

It might. Theoretically speaking, it might be easier to test whether this approach would work by blocking the egr output plate, and disconnecting the other end of the egr tube to the intake pipe. The output from the exhaust on the CRD that feeds the egr valve is at the back of the engine, right next to the firewall. Pretty tight in there. If this does work, it assumes the only check is the drop in fresh air flow as measured by the MAF sensor. This means letting the air control valve do its thing, and letting in fresh air into the intake behind the air control valve, using what used to be the input for the egr gas. However the fresh air gets there, via the intake tube opening directly or through the replumbed egr supply line from the other side of the engine, wouldn't seem to matter. Until a theory is tested, I would use the easiest approach to restore back original.

RFCRD · **Posted:** Sun Jul 16, 2006 6:59 pm

Ranger1 wrote:

It might. Theoretically speaking, it might be easier to test whether this approach would work by blocking the egr output plate, and disconnecting the other end of the egr tube to the intake pipe. The output from the exhaust on the CRD that feeds the egr valve is at the back of the engine, right next to the firewall. Pretty tight in there. If this does work, it assumes the only check is the drop in fresh air flow as measured by the MAF sensor. This means letting the air control valve do its thing, and letting in fresh air into the intake behind the air control valve, using what used to be the input for the egr gas. However the fresh air gets there, via the intake tube opening directly or through the replumbed egr supply line from the other side of the engine, wouldn't seem to matter. Until a theory is tested, I would use the easiest approach to restore back original.

Yep. The only thing is I believe it would need to be charged air fed to equalize the pressure and prevent backflow through the EGR.

Ranger1 · **Joined:** Mon Oct 17, 2005 7:40 pm **Posts:** 1137

Agreed. That might lead one to use the blocking plate on the egr output idea after all - nothing else needed there to keep pressurized air from the turbo leaking out via the egr to to exhaust connection.

RFCRD · **Posted:** Sun Jul 16, 2006 10:23 pm

Ranger1 wrote:

Agreed. That might lead one to use the blocking plate on the egr output idea after all - nothing else needed there to keep pressurized air from the turbo leaking out via the egr to to exhaust connection.

I would be happy to crack the software code to just turn the CEL off when it fails, plate the ports and be done with it. I understand that VW TDI owners do this all the time. The software parameters are completely adjustable with the right tools (laptop, software, & security code). When I first saw this engine in the late 90's at the Detroit Diesel R&D facility it appeared like they were controlling it with basic DDEC software, same as any Series 60 in a big truck or bus. I do know the security code for a bus is the last 4 digits of the VIN, backwards.

pokey555 · **Joined:** Fri Jun 09, 2006 2:47 pm **Posts:** 50

Correct me please, I am looking at the systems as two separate circuits, the idle air control (IAC) and the exhaust gas recirculation (egr). Can someone post a flow schematic or direct me to a link? The IAC is utilized to help with low speed idle control, and the egr pulls exhaust from the exhaust manifold and directs it into the intake. I was thinking of removing the tube between the exhaust manifold and egr (for experimental purposes) and blocking the port in the exhaust manifold, since it should be NPT or similar threaded port. And add a line from the air box into the egr input port. I would hope to learn from this exercise the following: Does exhaust soot contribute to egr failure? Is another emission component failing but is masked by the egr code first? Does the CPU utilize an incoming air temperature measurement in conjunction with flow rate to determine if the egr is working correctly? I would hope that this setup would not throw an egr fault for insufficient flow unlike the plate idea proposed by Ranger, and reduce costs for a tuner or programming to disable the code. This is based on my knowledge of ford modular engines. This may not be applicable here, even though both are just air pumps that use different fuels

Rob

Ranger1 · **Joined:** Mon Oct 17, 2005 7:40 pm **Posts:** 1137

There isn't an IAC idle control in the CRD. That's on the V6 Liberty gasolene engine and is little more than a valve that opens when the throttle plate is closed, to allow enough air in at idle to keep the engine running. The PCM activates that valve when it senses the need for more air at idle with a closed throttle plate.

The air control valve on the CRD is used for at least 2 different functions - one is to close shut on engine shutdown to keep the shuddering to a minimum and the other is to close down when egr flow is desired while the engine is running. When it closes down, it decreases air flow draw from the air filter box on the front side of the air control valve and increases draw on the egr supply line located behind this air control valve. If you block off the egr output and hook up the other end to the air box, you'll still get a code. I believe the reason to be that the MAF will not sense the expected reduced air flow when the air control valve is closed or nearly closed and the PCM then sets the code. This would be because of the increased air flow from your new connection to the airbox. The air into the intake must come from somewhere else besides the air filter box if the MAF is going to detect reduced air flow and send the correct signal to the PCM once the air control valve and egr are activated.

"Does the CPU utilize an incoming air temperature measurement in conjunction with flow rate to determine if the egr is working correctly?" If it does, then a cold air substitute for exhaust gas won't work unless a way can be found to heat it, as has already been suggested earlier. We just don't know yet.

You could block off the egr output and open up the intake tube egr port to fresh air just to see if you get a code. If you don't get a code, you still don't want to leave the intake open to unfiltered air - you need some kind of air filter that is also protected from water soaking.

Have no links to a flow diagram. The flow is from outside air, into air filter box, through the air filter, into the turbo input, out from the turbo into the intercooler, out of the intercooler and into the intake tube containing the air flow control valve. Also connected to the intake tube is the smaller pipe from the egr valve, but its on the backside of the air control valve.

Goglio704 · **Posted:** Mon Jul 17, 2006 11:09 pm

If someone gets serious about this and needs a filter and housing they should look at a unit for an air compressor or vacuum pump. McMaster Carr sells some. A web search for Solberg will also yield results. The units I'm thinking of have NPT ports in and out making them pretty versatile. They are available in anything from soup can to 5 gallon bucket and bigger sizes.

Joe Romas · **Posted:** Thu Jul 20, 2006 8:17 am

[quote="RFCRD:[/quote]

I was not as clear as I should have been. Easing the operating parameters won't always log an error code, just make it less likely. If there is a code, as long as it's "historic" and not "active" should not effect the e-check.

You don't by chance know if this Jeep will be subject to Ohio e-check? I don't even think the fuel cap is designed to pass their test.[/quote]

In Central Ohio, Franklin county, we are not subject to e-checks yet :lol:

But with the air alerts we've been getting lately I don't know why but I'm not looking foward to it :shock:

naturist · **Posted:** Thu Jul 20, 2006 8:47 am

The '05 CRD I've had EGR troubles with is Khaki, so I'm not buying the notion Khaki ones have fewer EGR problems.

It appears, based upon my experiences, that the two parts DC calls EGR valves (one in the exhaust gas stream with a part number ending in "AA" and one in the intake air stream with a part number ending in "AB") throw the same codes. I _THINK_ one of the things that the dealers get into is replacing the AA part when the AB one is the bad actor. I had the AA replaced 3 times before they did the AB, which seems to have cured the problem (knock on wood).

It should be noted that the AB valve probably does double duty, restricting intake air to control the air/exhaust ratio, and shutting off air on shut down to prevent shuddering/hard shut down. There is exactly such a valve on the VW TDIs, and VW calls it the "anti-shudder" valve, although it probably also acts to help control the air/exhaust ratio.

My guess is that they got EGR codes, and replaced your AA valve, but with hard shut-downs, you really need the AB valve, as yours is sticking open. For what it is worth, the AB valve costs about $600 for the part. I don't know what the AA valve costs, but it must be less, or why would DC stand for changing that multiple times before getting to the AB valve?

Tom_with_a_Dream · **Posted:** Thu Jul 20, 2006 2:09 pm

I've read the posts on removing this line and blocking that line, etc. It all makes sense, in the abstract, but I am not going to be doing that myself so maybe I have missed simething along the way. (Might have a mechanic do it once you all prove that it works and I am out of warranty, etc.)

But my question is this: Don't we want the EGR valve to dump exhaust back into the intake?

My CRD is in the shop as I type, all week so far and predicting into next week, for a 3rd EGR low flow (or similar). I drove it for over 2 weeks with the CEL, which came in about 10 miles from the shop after getting the TC replaced and the 2nd EGR. So I have not had a working EGR for months.

And my mileage can't get over 25 mpg. I was up near 27 prior to the EGR acting up, just getting past my break-in and all that. I can't help but think the mileage will go up if the engine is re-ingesting waste combustibles. Blocking the EGR may solve the code but won't it prevent us from the coveted 30 mpg?

Am I off-base here...

RFCRD · **Posted:** Thu Jul 20, 2006 3:23 pm

Tom_with_a_Dream wrote:

But my question is this: Don't we want the EGR valve to dump exhaust back into the intake?

This depends on your ecological perspective. The EGR valve is dumping exhaust gas (which has little or no usable oxygen) into the clean intake air to reduce peak combustion temps, thus reducing NOx emissions. ie... reduce the burn efficiency to get a marginal drop in NOx emissions. In addition, this exhaust gas contains contains gritty/abrasive soot which over time will trash your upper engine. It's the same effect as running without an air filter.

If you want to really uncork this motor for both performance and fuel economy, find a way to block the EGR ports and eliminate the airflow constriction from the anti-shudder valve. One additional thing not discussed is that you wouldn't need the anti-shudder valve to close to prevent after-run if you weren't sucking raw motor oil into the air intake.

Tom_with_a_Dream · **Posted:** Thu Jul 20, 2006 3:47 pm

This isn't an argument, despite the fact that it may seem that way, without benefit of tone and body language, etc. Here goes...

Quote:

The EGR valve is dumping exhaust gas (which has little or no usable oxygen) into the clean intake air

But it does still have usable combustibles, which if burned in lieu of fuel from the tank in back will improve your mileage. Very few combustors are 100% efficient, and by "very few" I mean NONE.

Quote:

reduce peak combustion temps, thus reducing NOx emissions

I don't know what you mean by "reduce the burn efficiency to get a mrginal drop in NOx emissions" but I do know that NOx production is highest at something like 1600F. So you are right that reducing the combustion event temperature, either by cooling the air or by introducing less fuel in more places within the chamber (Total fuel and BTUs introduced the same, overall. Talk to your local utility, they call it "staged combustion"...), will reduce NOx.

Quote:

exhaust gas contains gritty/abrasive soot

But didn't that stuff come from the cylinder? Aren't ours lined with something appropriate for this sort of wear?
Dumb Question Alert - Do gas engines produce less gritty soot? Part of me says yes, less gritty. Part of me says no, all combustion is gritty.

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I can see your point about uncorking the engine by closing all the EPA ports and jamming clean, cold air into the cylinder. But I am not concerned about beating the Mustang sitting next to me, I'm interested in 30 mpg on a 300,000 mile engine, that still gets 24 mpg pulling (pushing ?) a travel trailer.

EGR SNAFU

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