M110 running on 5, do these plugs tell a story? - PeachParts Mercedes-Benz Forum

79Mercy · #1 03-01-2012, 07:41 PM

While on the highway today it felt like the motor was sluggish when the pedal was pressed more and then like a switch flipped it had normal power again if i held the pedal down closer to the floor.

When I got to city streets i found out it was intermittently running on 5 and would sometimes hit on the 6th one. I could feel the engine "bucking".

Prior to this it would run on 5 cylinders randomly after start up for a few seconds but would always clear up. These plugs have less than 1500 miles on them...

I think my headgasket has a small leak in it as i have stated in some of my previous threads.

I pulled the plugs out when i got home, all of them look okay except number 4.

Im not sure whats going on in this cylinder, what do ya'll think is happening to make the #4 plug look like this?

79Mercy · #2 03-01-2012, 08:14 PM

Just installed a set of new plugs, still wont run on 6.

What could it be?

I pulled the dist cap and rotor off, all looks normal there.

alabbasi · #3 03-01-2012, 08:21 PM

I battled with this some time ago with my Euro 560SEC.
What I suggest is the following.

1) Crack the lines at the fd 1 by 1, you will hear the car change tone on all cylinders except the one that's giving you problems.
2) If you have a fuel related issue (fd or fuel injector) you can test by spraying carb cleaner into the intake which will feed fuel to all cylinders. If the car starts running as normal, then you know it's a fuel issue.
3) Second test here is to swap lines going into the FD and see if you can get another cylinder to act out, same with injectors.
4) If it's not a fuel issue, repeat the test by pulling plug wires out while engine is running in order to hone in on the cylinder
5) Once you know which one, swap plug wires around (at both ends of course) to see if you can get it to act out on another cylinder
6) Swap plugs.

You should at this point be able to tell if it's a fuel or spark issue. If you can't, then run a compression test.

79Mercy · #4 03-01-2012, 09:27 PM

I determind it was cylinder 4 which was giving my issue, i unplugged #4 wire and ran motor ran about the same, it just missed constantly since it wasnt plugged in.

I pulled the injectors out of 3 and 4, and i was able to blow straight through the #4 injector, i could blow through the #3 injector.

Im gonna call Phill in the morning and get a new fuel injector

werminghausen · #5 03-02-2012, 03:56 AM

As injector 4 is out you can check the filter piece on top. Maybe the filter is just clogged...as it still fires at full throttle?. You can also run carb cleaner through the injector for cleaning purposes. Not sure what you mean with 'blow through' injector 3 and 4.

t walgamuth · #6 03-02-2012, 08:25 AM

Since you have the plugs out you might want to go ahead and run a compression test.

mespe · #7 03-02-2012, 08:46 AM

Anyone else notice that the number 2 spark plug has a tinge of grey on the one side? firing order 1-5-3-6-2-4, could be 6 is way too lean, causing more fuel to be squirted late in 2's and entirely in 4's fuel delivery. and 6's tip looks consumed.

79Mercy · #8 03-02-2012, 09:30 AM

Quote:

Originally Posted by mespe

Anyone else notice that the number 2 spark plug has a tinge of grey on the one side? firing order 1-5-3-6-2-4, could be 6 is way too lean, causing more fuel to be squirted late in 2's and entirely in 4's fuel delivery. and 6's tip looks consumed.

Yes i noticed those spots when i pulled the plugs but had no idea what they were from. I think since number 4 was just pissing fuel in the motor the other cylinders were running leaner then they should.

When I said blow through the number 4 injector i meant i could blow air through it with my mouth. These injectors should pop at 40 PSI if i recall correctly.

werminghausen, what filters are you referring to, i dont think there are any filters on the injectors.