[RunningTooHot]

This seems rather simplistic, but I'd like to confer with you guys to make sure I'm thinking straight. One of my 2001 E320's, Is getting a recurring P2001 EGR code.

The engine will sometimes idle normally; it's very smooth. Other times it is choking & missing horribly at idle. I am thinking this is indicative of the EGR valve intermittently getting stuck in the open position during idle. (I am also assuming that the EGR to intake manifold tube is not plugged, otherwise there would be no flow.)

Here's the question: Do you feel it's worthwhile to attempt to clean the EGR valve, and what are the odds it may be successful? (The diaphragm must be good, otherwise it wouldn't function at all.) I know that for $100, I could just replace it, but I don't drive that car very much and just need to pass an upcoming smog check.

On a secondary note, I keep getting a P203D code for "implausible camshaft variation angle". The cam sensor is absolutely known to be good, and I've traced continuity through the wires back to the ECU - it all checks out OK. Plus, my scanner shows the cam sensor as "running" when viewing live data. I'm kind of thinking that the extremely rough running & misfiring at idle due to the EGR problem may be playing havoc with whatever slack there may be in the timing chain, thus causing the cam sensor to pick up varying angularity readings and throw a tantrum. Curious to know your thoughts on that hypothesis.

As always, thank you in advance for your willingness to share your expertise!

 

[khomer2]

When was it last cleaned or replaced?
Have you checked all the associated vacuum lines (cracks disconnects etc) and the valve itself to see if it's functioning correctly.

 

[RunningTooHot]

No EGR service history available, so it's an "IDK".
No vacuum leaks, disconnected, or cracked hoses.
Switchover valve and EGR valve itself are functioning, otherwise there would not be any EGR flow - which is what (I believe) is causing the intermittent choking/rough idle.
That's why I'm thinking the EGR valve itself is sometimes sticking open... unless I hear otherwise.
Just wondering how often that is a failure mode, and if it is a reasonable expectation that cleaning & lubing the sliding portions would work to solve it.
I wouldn't be asking this, other than I've got a bad back, and I don't want to R&R it twice... nor do I want to spend the money for a new valve if not necessary. (If it were a daily-driver, I'd just buy a new valve, but this car is not driven much.)

 

[khomer2]

Ok so you've tested and know for sure the valve is good.

You know your 2 choices then based on your parameters.

 

[mrboca]

This seems rather simplistic, but I'd like to confer with you guys to make sure I'm thinking straight. One of my 2001 E320's, Is getting a recurring P2001 EGR code.

The engine will sometimes idle normally; it's very smooth. Other times it is choking & missing horribly at idle. I am thinking this is indicative of the EGR valve intermittently getting stuck in the open position during idle. (I am also assuming that the EGR to intake manifold tube is not plugged, otherwise there would be no flow.)

Here's the question: Do you feel it's worthwhile to attempt to clean the EGR valve, and what are the odds it may be successful? (The diaphragm must be good, otherwise it wouldn't function at all.) I know that for $100, I could just replace it, but I don't drive that car very much and just need to pass an upcoming smog check.

On a secondary note, I keep getting a P203D code for "implausible camshaft variation angle". The cam sensor is absolutely known to be good, and I've traced continuity through the wires back to the ECU - it all checks out OK. Plus, my scanner shows the cam sensor as "running" when viewing live data. I'm kind of thinking that the extremely rough running & misfiring at idle due to the EGR problem may be playing havoc with whatever slack there may be in the timing chain, thus causing the cam sensor to pick up varying angularity readings and throw a tantrum. Curious to know your thoughts on that hypothesis.

As always, thank you in advance for your willingness to share your expertise!

It sounds like a rational thinking that the EGR valve is stuck open and causing the problems you are having.

So, if you disable the EGR activation, none of these problems would not occur, right? If you remove the EGR solenoid connector, you will get an immediate fault code, but the ECU will not be able to open the valve even it wanted to.

Clear the codes, and drive the car with the EGR solenoid connector disconnected. If you have smooth idles, and no other codes (apart from the P0400 equivalent of EGR fault), then you know, it is the valve staying stuck open issue. If you however still get rough idles, you would then know it is something else. This will help you analyze causes and effects.

 

[Deplore]

Mileage?

EGR valve does stick open and/or oval the piston rod enough to induce vacuum leak. My E55 on the original EGR valve was failing smoke test, because smoke was coming straight out of the EGR valve itself....but E55 also has 270k on the clock.

 

[RunningTooHot]

Mileage?
EGR valve does stick open and/or oval the piston rod enough to induce vacuum leak. My E55 on the original EGR valve was failing smoke test, because smoke was coming straight out of the EGR valve itself....but E55 also has 270k on the clock.

Not quite sure of the mileage because this car apparently had the odometer altered at some point. My best guestimate is about 230,000 miles based on carfax data.

It sounds like a rational thinking that the EGR valve is stuck open and causing the problems you are having.

So, if you disable the EGR activation, none of these problems would not occur, right? If you remove the EGR solenoid connector, you will get an immediate fault code, but the ECU will not be able to open the valve even it wanted to.

Clear the codes, and drive the car with the EGR solenoid connector disconnected. If you have smooth idles, and no other codes (apart from the P0400 equivalent of EGR fault), then you know, it is the valve staying stuck open issue. If you however still get rough idles, you would then know it is something else. This will help you analyze causes and effects.

Well, it's good to get verification that I'm still capable of rational or logical thinking. That not always a sure thing, which is why I wanted to check with you guys.

In fact, your suggestion is a great example of a simple diagnostic step that I did not think of. Thank You! I'll try that out and hopefully it will help substantiate or verify the cause. I'll post again after a couple of days of running it disconnected.

 

[mrboca]

Mileage?

EGR valve does stick open and/or oval the piston rod enough to induce vacuum leak. My E55 on the original EGR valve was failing smoke test, because smoke was coming straight out of the EGR valve itself....but E55 also has 270k on the clock.

Stuck open valve is stuck open valve, and if it is permanently stuck open, you would get rough idle all the time. If it is intermittent, then something must be causing it to be unstuck. Typically the EGR activation will not take place, if there is EGR related fault (valve, solenoid, clogged pipe, MAP sensor, MAP sensor vacuum line).

 

[Deplore]

Mine was not stuck open. No exhaust gas entering the intake when not commanded, etc. But it had unmetered air entering into manifold through the valve itself.

That is to say, the plunger blocking the EGR was fine. The pieces after the plunger, on other hand, were not airtight.

 

[RunningTooHot]

Stuck open valve is stuck open valve, and if it is permanently stuck open, you would get rough idle all the time. If it is intermittent, then something must be causing it to be unstuck. Typically the EGR activation will not take place, if there is EGR related fault (valve, solenoid, clogged pipe, MAP sensor, MAP sensor vacuum line).

The intermittent nature is exactly why this is a bit perplexing. It seems that either A.) the vacuum solenoid is sometimes sticking open, or B.) the EGR valve is sometimes sticking open, but eventually the spring overcomes the resistance and snaps it shut again... until the next time the ECU calls for EGR flow.

I'm assuming (usually a dumb thing to do) that the EGR pipe is not plugged, otherwise there would be no flow capability to (intermittently) screw up the idle. The MAP sensor vacuum line is okay, I've never received a MAP sensor fault code and can see the live data fluctuate. Also of note is the MAF sensor is a known good unit, and the fuel mixture trim adaptations are not out of whack. There are no vacuum leaks, per the old 'spray a bunch of aerosol solvent around and listen for changes' method.

Mine was not stuck open. No exhaust gas entering the intake when not commanded, etc. But it had unmetered air entering into manifold through the valve itself.

That is to say, the plunger blocking the EGR was fine. The pieces after the plunger, on other hand, were not airtight.

That's an interesting failure mode. If I'm understanding this correctly, the vacuum diaphragm was still intact, but air was leaking around the rod going from the diaphragm canister into the body of the valve? That would be a tricky one to figure out!

I'll be driving the car later today with the electrical connector off, and I'll get back to you guys with the results.

 

[mrboca]

The EGR solenoid controls a 3-way valve. When the solenoid is activated, it applies vacuum to the EGR valve. When the EGR solenoid is deactivated, the intake vacuum port side is is blocked, and the vacuum in the EGR valve is released through the EGR solenoid exhaust valve (which has a filter on it as it allows air in the engine compartment into the EGR valve so it can be released (closed)). If you have a problem in the 3-way valve, you may have a vacuum leak through the EGR solenoid exhaust valve, and that seem to be what Deplore is talking about. Sometimes the solenoid valve gets stuck, sometimes it is worn out ,and leaks.

I'm assuming (usually a dumb thing to do) that the EGR pipe is not plugged, otherwise there would be no flow capability to (intermittently) screw up the idle. The MAP sensor vacuum line is okay, I've never received a MAP sensor fault code and can see the live data fluctuate. Also of note is the MAF sensor is a known good unit, and the fuel mixture trim adaptations are not out of whack. There are no vacuum leaks, per the old 'spray a bunch of aerosol solvent around and listen for changes' method.

You are assuming that the idle issue is due to EGR fault. But you need to confirm it, as you will be doing by disabling the EGR. You can also remove the hose from the EGR solenoid to the EGR valve and apply vacuum while the engine is idling. If it causes the same rough idle, you know that the EGR pipe is not clogged. If it does not do anything, then you have a problem with some other part of the EGR which generates this fault.

Regarding the MAP sensor, you only get a MAP code if there is an electrical issue with the MAP (open circuit short circuit etc.). If you have a small vacuum leak (hose from the intake manifold port, broken / cracked ports at either side), you will still get a reading which will not be correct.

 

[RunningTooHot]

Thank you! That's great info to learn how the solenoid / vacuum circuit functions, as well as the limitations for the fault code generation of the MAP sensor. On that car, the MAP vacuum line (and other vacuum lines) are in great shape - having been replaced with silicone hose.)
The first thing I wanted to do after getting recurring P2001 codes was to directly apply vacuum to the valve to test it. Unfortunately, the combination of huge hands plus the intake tube routing on the W210 precludes access (unless taking off the tube). That's the reason for all this speculative screwing around. My apologies for that aspect of this!

 

[RunningTooHot]

UPDATE:
After pulling the electrical connector off the vacuum solenoid valve, the engine idles smoothly at all times now; no more intermittent periods of rough idling. Thank you again MrBoca for that diagnostic suggestion!

The problem is now distilled down to 2 possibilities: 1.) the EGR valve itself sticks open intermittently, or 2.) the vacuum solenoid valve sometimes sticks open.

I'll try cleaning the EGR valve. As for the vacuum solenoid, please tell me your thoughts on this:
I'm thinking of spraying some brake cleaner through the solenoid valve, while applying voltage on & off to cycle the valve and allow full penetration of the solvent. Or would you suggest using something less aggressive, such as electrical contact cleaner?
Assuming I survive that without everything bursting into flames due to an errant spark, the question is if it would be a good idea to spray some form of lubricant (maybe silicone?) through it as well.

 

[mrboca]

In my opinion, the solenoid is acting up. I had the same problem before. As i never checked the EGR pipe, I thought it could be plugged too. I bought a second hand EGR valve + EGR pipe combo from EBay from a low mileage donor for about $30, including shipping, and replaced the whole thing. The EGR pipe was half clogged for a 190K miles car which would not cause any problems with gas injection.

After I replaced the EGR valve + pipe, I tested the old one. The EGR solenoid was leaking. I tested offline with a power supply and vacuum pump. I sprayed some Electronic connector cleaner, and it fixed the issue, how permanent, I do not know. If I have to replace the EGR system again (I cleaned the pipe completely), I would spray a bit of silicon spray, and test it for few days prior to installation.

Try spraying some CRC cleaner, and a bit of silicon. Also remove and clean the exhaust port filter, if you can.

 

[RunningTooHot]

Great to know! Based on that info, I'll try to save some work (and my aching back) by trying to clean the solenoid valve while it's in place. (If I can access it.) If that doesn't work, then I'll pull the EGR valve. Thank you again - MUCH appreciated!

 

[RunningTooHot]

I pulled the air intake tube for access. Took off the vacuum line at the diaphragm canister. Confirmed that the EGR valve IS working properly with both a vacuum pump AND by energizing the solenoid with the engine idling.

With the engine running, I sprayed CRC brake cleaner into the line while activating the solenoid on & off many times. Followed that with a short blast of silicone spray. If anyone tries this in the future, a note of caution to not suck too much silicone spray into the engine, as this (IIRC) could contaminate the O2 sensors or catalysts.

To pass a smog check, the car will need to go through several 'drive cycles' without throwing a code. I'll follow up in a few days to let you know. Keeping my fingers crossed that this 'lazy man's' approach may work.

EDIT: I just thought of something. While 'in there' I should have pulled off the vent line/valve to check or clean it. Theoretically, if that doesn't allow the line to vent, it could prevent the EGR valve from closing. That's IF I'm correctly understanding MrBoca's explanation of how the vacuum circuit functions.

 

[mrboca]

Yes you are right. If there were no vent port, the EGR valve would have stayed stuck open as soon as vacuum is applied. The vacuum has to be vented to restore the closed status of the EGR valve. This is the same as the secondary air injection switchover valve. It has a vent too to get the reed valves close by venting the vacuum from the combi or shut-off valves.

If the vent line is plugged, the vacuum will not be vented out and the EGR valve will stay open.

If this happened on the SAI switchover valve, the SAI pump would be filled with exhaust crud.

 

[RunningTooHot]

A follow up post for the results: SUCCESS!

It worked! Many thanks to mrboca, Deplore, and khomer2. I'm going to write up a separate post to help people find this potential fix more easily in the future.

After cleaning the solenoid as described above, the engine has been consistently idling smoothly, except for one single time on the 2nd day where it stumbled for a few seconds. It registered a pending code, but that's it. Nothing since that one incident. Ever since that... it runs properly. The car even passed the draconian State smog check today.

THANK YOU!