need help!!! 99 e300 engine shaking/missing - PeachParts Mercedes-Benz Forum

darkostoj · #1 07-16-2010, 09:07 AM

well i've had this problem for a month and i've been trying to fix it for a while with no luck.

it just hit 200k and the problem just started.

When I'd start the car it would idle very rough when cold, but smooth out as operating temp went up...but still never go away. This was only noticeable at idle.

I put new engine mounts in and they were fine, no improvement

I ran 2 cans of lubro moly through the injectors and put in a new fuel filter. No change

Even though my glow plug light worked normally I decided to change them out and clean the intake/egr since who knows when its been done last. I had 3 seized glow plugs and 3 came out easy. After 3 days I was able to get 2 of the seized out and one of them broke in the head. I got the broken one out (PITA!!) and got the new ones installed. It looks like the ones I pulled out were original MB ones, so maybe they were never changed. I got it all back together and now its running worse.

It still vibrates at idle, and now there is a noticeable miss/hesitation when you just depress the gas pedal. And if I give it a quick rev I see some smoke shooting out from under the intake. I looked around and didnt see where it was coming from.

I don't know what else to do here...I need to have this running again!!!

barry123400 · #2 07-16-2010, 11:16 AM

Since you just put new glow plugs in. If you own a cheap digital meter. The fastest way to determine if it is one cylinder or not in my opinion and which one.

Start the car. Unplug the glow plug harness. Read the milli volts on each glow plug wire as soon as the engine warms up a little still having the rough idle. The ground wire of your meter must be grounded on the engine for this test. A point like the valve cover and not the negative battery terminal.

The one glow plug that is seriously low voltage by a good margin is the offending cylinder of course.. We will for assumptions sake assume you found the low voltage cylinder. If so swap the injector with any other injector you like. If the vastly reduced voltage moves with the injector you have a bad injector. If not then do a compression check on that indicated cylinder.

At this point or sooner if you do not get a lower voltage on one plug mention everything you did on site. Even if you get a low voltage and I think you probably will.

The important thing here is to establish for certain that it is one cylinder not a general overall fuelling issue where the roughness is caused by another condition and displays itself by inconsistant cylinder firings across the engine.

This test is best done with more current glow plugs like your. As as they age usually there will be some changes between individual glow plugs that mean more effort is required in this test. This is perhaps the quickest and most conclusive test available in my opinion. Record each cylinders voltage readings as well both for future refference and they will indicate other things if they are present.

You will have to use the lowest milli volt scale on your meter remember. The glow plugs normally only produce usually about 8-20 millivolts output

Jeremy5848 · #3 07-16-2010, 11:54 AM

You can also do this test using the resistance (ohms) scale of the DVM. The resistance of the glow plugs increases with heat; a glow plug in a cylinder that is mis-firing won't get as hot and its resistance will be lower. Since the low plugs have a resistance of less than 1 ohm, you will need a very sensitive meter. If you don't, then Barry's method is better.

Jeremy

darkostoj · #4 07-16-2010, 12:03 PM

ok guys, I tore it all apart again and the egr clamp wasn't on properly. It sounds like it runs much better now with the new plugs, but it was just idling. I'm going to take it for a drive to see how it does after work