amuso

I've had this problem for a while now, but it got more worse this summer.

Now at idle the car will surge. It drops perhaps 100-150 rpms and catches up again. It does it say about once a minute or more. When you drive it and barely give it gas you can also feel it surging. At any speed I'd say.

The car will soot a lot when you gas it as well.

I tried an EGR-delete solution with a couple of resistors and a diode, but that just led to limp mode. So I removed that hack.

I have however found a temporary solution by disconnecting the EGR vacuum line from the pressure regulator, and blocking of the out line from the pressure regulator.

However this causes the car to be a bit sluggish after 2-3 minutes of driving. It will rev past 3000 rpm all the way, but is very very slow to pick up until after 2700-2800 rpms. Then it "wakes up" again. No problems from stand still though. It picks up great and seems to have all power. It's just when cruising that it is slow to pick up. If you floor it, it will shift down and pick up but not with full power until 10-15 seconds. Sort of a half-limp mode. Or extreme turbo lag.

Thinking it was either a sooted up EGR valve or pipes I cleaned those today. Removing a lot of junk from the pipes and valve.

This did not solve the problem. Still surges at idle and when in gear it almost stalls. Actually has once when it was cold.

So I removed the hose from the EGR valve to inspect it's operation while running. I can see the EGR working after starting. It opens the valve and then slowly closes it after a minute or two. This makes me think the EGR and pressure regulator is working.

I also tried bypassing the pressure regulator to keep the EGR open at all times. That resulted in stalling after approx 1 minute after startup.

I am trying to figure out what can cause the surging. Since disabling the EGR vacuum pipe completely solves the surge, but results in a bit sluggish response when I cruise I am not sure if it is the MAF.

Any ideas or tips from anyone ?

Plutoe

FYI----we have a diesel forum where all the smokers love to exchange their prowess!!

amuso

Thanks for the tip.
I actually solved this today… After reading a few more articles I stumbled across something that was very similar to mine, and I decided to retry the EGR disable mod I've tried before.

1) The last time I did the mod, I accidentally connected into the turbo pressure regulator instead of the EGR pressure regulator. I discovered this today when I decided to reinstall the mod. I'd mistaken red/black with red/white and grey/black with grey/white. I installed the mod as per this guide:

http://forums.mercedesclub.org.uk/sh...ad.php?t=68928

2) I also followed a tip towards the end of this thread:

http://forums.mercedesclub.org.uk/sh...ad.php?t=69562

The other user had swapped the turbo and EGR pressure regulators. They have the same part number. I verified it with the EPC software and visually on the devices.

After doing these two mods the car now runs great! Lots of power. No idle surge. Almost no black smoke when flooring it. Look forward to tomorrows 80 mile commute to see if the good old Star quality and comfort has returned