I replaced the spark plugs, but I'm still getting faults from 3 cylinders. Any thoughts before I move to replacing the coils?

What were the faults?
Those 137 engines were a PITA to diagnose some times, were any of the red boots burnt? You replaced them all when you did the plugs, right?

how about oil in the harness?
if all your faults are 3 adjoining cyls, I'd look to a possible o2 sensor.

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1980 500SE/AMG Euro
1981 500SEL Euro
1982 380SEL
1983 300TD
1983 500SEC/AMG Euro
1984 500SEC
1984 300TD Euro
1986 190E 2.3-16
1986 190E 2.3
1987 300D
1997 C36 AMG
2003 C320T 4matic

past: 1969 280SE 4.5 | 1978 240D | 1978 300D | 1981 300SD | 1981 300SD | 1982 300CD | 1983 300CD | 1983 300SD | 1983 380SEC | 1984 300D | 1984 300D | 1984 300TD | 1984 500SEL | 1984 300SD | 1985 300D | 1986 300E | 1986 560SEL | 1986 560SEL/Carat | 1987 560SEC | 1991 300D 2.5 | 2006 R350

Yeah the good old M137. Anyone who's been around MB's for awhile understands why this engine didn't hang around too long. The CSO feature (cylinder shut-off) wasn't a bad idea, it just had some unintended consequences.

For those who don't know how it works, here it is. Under certain driving conditions, the left bank of cylinders was shut down to improve fuel economy. The resulting temperature and pressure change caused some blow-by, eventually putting enough engine oil into the intake manifold to start fouling the spark plugs. Believe it or not, a slight mis-fire on the M137 is almost undetectable to the driver. Because of this, the situation would gradually worsen, resulting in damage to the ignition coils.

The fix is pretty straight-forward. Replace the plugs, coils, and insulating boots. Then, remove the intake manifold and clean out all the oil to prevent a re-occurrence of the plug fouling. When this is done, drive the car to a shop equipped with SDS. With SDS, the sensitivity for mis-fire detection can be decreased by means of a software update, resulting in fewer "false alarms". Lastly, use SDS to disable the CSO feature (after all, CSO started the whole mess to begin with).

There are a few other scenarios, but back in the day, this was the most common. Since then, the ignition coils have been improved. In fact, I rarely see the newer version cause any problems.

Check to see if your coils havent been replaced already as well, the new ones part # starts with "275."

Pray to god your oil cooler doesnt start leaking either Time to sell the car if that happens!

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1980 500SE/AMG Euro
1981 500SEL Euro
1982 380SEL
1983 300TD
1983 500SEC/AMG Euro
1984 500SEC
1984 300TD Euro
1986 190E 2.3-16
1986 190E 2.3
1987 300D
1997 C36 AMG
2003 C320T 4matic

past: 1969 280SE 4.5 | 1978 240D | 1978 300D | 1981 300SD | 1981 300SD | 1982 300CD | 1983 300CD | 1983 300SD | 1983 380SEC | 1984 300D | 1984 300D | 1984 300TD | 1984 500SEL | 1984 300SD | 1985 300D | 1986 300E | 1986 560SEL | 1986 560SEL/Carat | 1987 560SEC | 1991 300D 2.5 | 2006 R350

the parts quote i got on the coil packs was 1250 per. i'd heard they were below a grand . . . guess not. great car, when it runs.

oil in the harness too. didn't get a fault on the O2 sensor though.

oil in the harness can cause some weird stuff. replace the leaking pressure sensor on the front of the left cylinder head asap and clean out as many connections as you can find with oil in them.

__________________


1980 500SE/AMG Euro
1981 500SEL Euro
1982 380SEL
1983 300TD
1983 500SEC/AMG Euro
1984 500SEC
1984 300TD Euro
1986 190E 2.3-16
1986 190E 2.3
1987 300D
1997 C36 AMG
2003 C320T 4matic

past: 1969 280SE 4.5 | 1978 240D | 1978 300D | 1981 300SD | 1981 300SD | 1982 300CD | 1983 300CD | 1983 300SD | 1983 380SEC | 1984 300D | 1984 300D | 1984 300TD | 1984 500SEL | 1984 300SD | 1985 300D | 1986 300E | 1986 560SEL | 1986 560SEL/Carat | 1987 560SEC | 1991 300D 2.5 | 2006 R350

only getting faults from one side. any reason to replace the coil on the other side?

Exactly which cylinders are throwing the fault codes? Are they always the same, or is it random?

consistently 10, 11 and 12

We have a winner!!! Cylinders 10, 11, and 12 all report to the same O2 sensor. This is where you need to look first, although it's still possible that the coil assembly is the problem.

12 cylinders = 24 spark plugs, I guess.
Spark plugs change at dealership must be around $800 :-)

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1996 E320 since 1/16/08, 171K miles as of Feb 2011

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1989 300CE - R.I.P. Dec 29 2007
Other MBs (sold): 1992 300E-24 - 1979 350SLC - 1984 230E - 1990 300CE