400 SEL BREAKING UP AROUND 1500 RPM - Page 4 - PeachParts Mercedes-Benz Forum

William73 · #46 02-19-2010, 12:57 PM

Little guys under the hood doing anything would be awesome. Git your camera ready!

PETERPNYC · #47 02-20-2010, 01:56 AM

Quote:

Originally Posted by 400Eric

Test for arcing already!
You'll be able to see some arcing even during the times when you are not experiencing symptoms.
Regards, Eric

Well waited till dark and after dinner me and my cousin opened up hood to see if there was any arcing.
We took off air filter housing and removed drivers side plug cover, no arcing. Decided to pull passengers side plug/wire cover off , absolutely no arcing.
Was sure to wait till engine temp got to over 8O Celsius no arcing . Looked at the wires when at idle, and loaded engine in gear no arcing .
I saw the 3 suppressor wires that dealer/ mechanic had said he changed, they were red colored caps so now at least I know which cylinders he thought might be suspect. Plug wires looked really good , even my cousin said he was surprised that after 17 years they were supple not dried or cracked or anything. No arcing at all
Looking around engine compartment to get an idea if anything else was obviously wrong and we found a vertical plastic hose coming out of a bundle that went in to an L shaped black rubber hose that connected to what looked to him like an EGR valve that is aprox 8-10 inches in left hand corner in front of the throttle body.

It is seen in the front left hand corner of the second photo of post #9 in

http://www.benzworld.org/forums/w140-s-class/1493456-s420-sel-breaking-up-under-load.html

In case the photo does not come thru I will describe it as best as I can.
The part that the broken hose went in to was approx 1 3/4 inches in diameter and looks like a flying saucer .

Well since the plastic hose was broken off about 1/4 inch from where it went in to the black rubber hose we pulled the broken plastic part out.

There was not much play left in rubber hose but it seemed we were able to reverse the L shaped hose, and sorta stretch it and get it back on the valve. We thought we found the problem . Drove the car and it made no difference .

My cousin was not sure that the stretched hose was making a good connection and allowing the vacuum to function, so we left the hose off the valve entirely and I drove home 25 miles. Car drove perfectly without hose attached at all, and did not exhibit any hesitation, when I got back to city upon aggressive accelleration. I did not expect it to ,as highway driving kept engine temperature around 60C and it usually only happens after 80 C is reached.
It is possible that the repair we made stretched the hose so the vaccum could not function properly , but if that in case, is not the fact, then what is this valve that made no difference being unattached ?
So no arcing, and since it is past midnight , I will buy a new L shaped hose and attach it tomorrow and hope that is the problem.

It also is possible the 2 mechanics messing around in the engine compartment changing plugs ,and then rotors broke the hose/plastic piping .

If so why put a useless vacuum line in a car ?

Still lost

William73 · #48 02-20-2010, 03:08 AM

It sounds like you are onto something.

PETERPNYC · #49 02-20-2010, 03:10 AM

This is the correct photo. The part is to the right of the oil filler cover, and in the front to the left of the throttle body with a black vacuum hose coming out of the top of it.

It is round like a saucer . What is it called and what does it do?

emerydc8 · #50 02-20-2010, 07:24 AM

It's an Exhaust Gas Recirculation (EGR) valve. Most cars have them. They are easy to change.

PETERPNYC · #51 02-20-2010, 09:59 AM

Quote:

Originally Posted by emerydc8

It's an Exhaust Gas Recirculation (EGR) valve. Most cars have them. They are easy to change.

OK. Now could a vacuum line broken to this EGR valve cause a hesitation upon accelleration when the car is warm and other problems ?

William73 · #52 02-20-2010, 04:34 PM

Did you say it ran better with the vacuum line disconnected?

PETERPNYC · #53 02-20-2010, 05:25 PM

Quote:

Originally Posted by William73

Did you say it ran better with the vacuum line disconnected?

It ran the same which was basically because I was doing highway driving and engine never gives me problem on highway or when engine remains cool.

Then today I put on new hose to EGR valve and drove around for 40 minutes in city traffic . Up hills and not a stall at all . Engine temp got to 98C and I drove up a 15% hill to really put it under load and it drove fine.

Then I stopped for a cup of coffee and after 15 minutes started her up and without waiting 30 seconds, pulled away on a flat road, and it hesitated again at 84 Celsius . Drove for another 5 minutes and did not happen again .

Stopped for a half hour and then drove for another 10 inutes No problem again.

Stopped for dinner about 80 minutes and then drove it around again for another 10 minutes (temp near 80 C) no problems. Any way the EGR could have caused all my problems ?

Anyone think the hose to the EGR all by itself , made it better and the computer has to relearn something thus the one time flat spot/ bogg down ?

If so , which I hope is true, it cost me $700 for a 50 cent piece of hose!

emerydc8 · #54 02-20-2010, 06:01 PM

This may help you to understand the EGR. It's #7 in the link below.

Quote:

1994 E320 EGR Problem

From your description, it actually sounds like your egr valve is stuck in the open position. There is no "internal engine valve dealing with the EGR system". The only component of the egr system is the egr itself.

Here is how the system works.

There is a way to check if your EGR valve is not working due to a plugged up hot inlet pipe, or if the valve itself is sticking (sticking in the open position or sticking in the closed position.):

The ECU sends an electric signal to the switch-over valve which opens the EGR valve to engine vacum. The vacum pulls open the diaphragm on the EGR, allowing some of the exhaust gas to recirculate back to the intake manifold (thus the name, Exhaust Gas Recirculation). The purpose is to reducing emissions.

The ECU will not send this electric signal at idle or wide open throttle, or until the engine has warmed up. So, if you hand pull about 12" of vacum on the EGR at idle with a warm engine, you are creating a very lean condition (vacum leak) and the engine will attemp to stall and run very rough. This tells you not only that the EGR is opening, but also that the hot inlet pipe is not completely plugged up. If, when you pull vacum and nothing changes, then you know that either the valve is not opening up, or the hot inlet pipe is completely blocked.

Now, release the hand vacum and the EGR should snap shut. Engine should smooth out.

In your case, your car is idling rough when cold, and the problem cleared up when the engine warmed up. This describes an egr that is stuck open.

There is another possibility that the diaphragm in the EGR itself may leak and cause an internal leak. The test for this is to see if the hand vacum will hold the EGR open for a period. It is common on vacum leaks to not be as noticeable with a cold engine as the engine is running rich and that helps off-set the added intake of air caused by the leak.

Last, when you clear the check engine light, it takes the same fault to occur over a specific period of time for the check engine light to come on again. It may take a few days, or even a week, but it will come on again.
__________________
Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

PETERPNYC · #55 02-20-2010, 08:33 PM

Quote:

Originally Posted by emerydc8

This may help you to understand the EGR. It's #7 in the link below.

Emery please read my above post #53 which I have edited. My problems were not inspection emissions related but much more serious hesitation/ stalling problems that at least for the moment have improved tremendously, or gone away completely . ( I say this after only 5 quick trips , with one appearance of the problem)

Simple question is can a broken hose ( loss of vacuum ) to the EGR cause those types of problems. Can anyone answer that question and no more info needed.

William73 · #56 02-20-2010, 09:28 PM

Quote:

Originally Posted by William73

Don't give up. It usually turns out to be something simple that makes an engine not run right.

I think you found the "something simple".

emerydc8 · #57 02-21-2010, 12:55 AM

I think it's possible, but you said that the problem hasn't entirely gone away or maybe not sure it's gone away. Maybe it's something entirely different like the ignition coil going bad. You're not getting any DTC's at all?

400Eric · #58 02-21-2010, 05:50 AM

I can't see how this would cure it completely. The EGR is only active under part throttle conditions anyway and that vacuum line is not big enough to cause a big enough vacuum leak to cause your symptoms. Report again after you have driven it on a longer trip and with higher engine temps.

I have to ask: Are you sure you were in a truly dark area when you looked for the arcing? It has to be pitch black. My spark plug wires on my 93 400E were in very bad shape when I bought the car 4 1/2 years ago with about 125,000 miles it. They were arcing and the car ran poorly when one asked for acceleration from it (like yours). My 95 E420 had about 170,000 miles on it when I got it about 3 months ago and it's wires are absolutely rotten. I do not believe your wires could still be good if they are the original ones. Has it been established for sure if these wires have ever been replaced or not? It is a common misconception that these MB spark plug wires don't go bad because they are solid core (as opposed to carbon core wires which do go bad much more frequently). But even these solid core wires go bad because the insulation somehow for some reason slowly stops "insulating". I don't know why. I don't know if it's age related or miles related or both. Don't discount the spark plug wires yet.

Another thing I'm wondering about now is the engine wire harness. It is a known problem of MBs of that time period. The insulation of the wires literally turns to dust but it's difficult to spot because the areas where the wires are exposed look fine. It's the areas that are the most hidden where the rot is the most pervasive. I think it has something to do with the fact that a more hidden area will keep moisture longer. This would need to be checked out by someone who is familiar with the problem. Maybe a member of this board who lives in your area can help you check this out.

The good thing about both of my suggestions is that you can check and see if you need to replace these FIRST, without having to buy anything unless you confirm that you in fact need to.
Regards, Eric

emerydc8 · #59 02-21-2010, 08:19 AM

Quote:

There is no check engine light on my car but ABS, ASR, OIL, ENGINE TEMP, BRAKES, LIGHTS, and any other idiot lights that should be operational on the DASH are working so I have not missed any CEL codes

I just wanted to make sure I understand what you're saying here. When you turn your key to position 2, you do not see a check engine light?

PETERPNYC · #60 02-21-2010, 08:43 AM

Quote:

Originally Posted by emerydc8

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I just wanted to make sure I understand what you're saying here. When you turn your key to position 2, you do not see a check engine light?

When I turn my key to position #2 I see every light on the instrument cluster light up, but none of them is a CHECK ENGINE LIGHT. There ia a light for ABS,BRAKE, ENGINE, COOLANT, OIL, LIGHTS, SRS, ASR and a few more that I do not recall .

There are a total of about 9-10 lights that all are working but no one light specific for CEL .

What would it look like and what would it be called . I do not believe there is any more room on my instrument cluster for any more lights , and all the lights there work

.

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