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

William73 · #1 02-20-2010, 04:34 PM

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

PETERPNYC · #2 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 · #3 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 · #4 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.