I took the time to write a nice piece on the difference of these engines.

I found it and will copy and paste it here:

1990-1992 300CE's have a different M104 engime (M104.990). This 3.0 liter-24 valve M104 engine is an early version of the 24-valve DOHC 3.2 liter M104 engine used from 1993-on. The 3.0 liter version still used the CIS-E fuel injection system as 1986-1992 3.0 liter M103 engines, using a distributor with one coil wire and 6 spark plug wires. This is basically a mechanical injection system with electronic control.

The 3.2 liter M104 engine uses a different ignition system - HFM (hot-film mass air flow sensor), fully electronic with integrated electronic ignition and sequential fuel injection. This system combines fuel injection and ignition control in one module. HFM-SFI systems use coils that are mounted directly on the spark plugs, replacing the distributor at the front of the engine. Each coil pack provides spark to two spark plugs at the same time, one connected directly to one plug, and the other with a short high tension lead to the next spark plug. So there are 3 coil wires and 3 high tension lead wires.

HFM fuel injection systems are designed so that idle speed can't be adjusted. Idle speed is completely controlled electronically. This HFM injection system also has adaptive technology that compensates for conditions such as engine wear and unmeasured intake air and is designed to maintain driveability as the engine ages.

HFM-SFI can retard engine knocking to just the knocking cylinders, unlike EZL technology, which retards spark timing across the entire engine. This keeps the ignition timing point as advanced as possible for maximum power output.

The 3.2 liter M104 engines also have variable valve timing on the intake cam, making the torque curve broad and flat, developing HP at a much lower rpm. This makes the power much more useable and noticeable.

The problem with the M104 engine, in my opinion, is that they are more expensive to run. Why?

Early M104 engines had head gasket problems. Also, all 1993-1995 Mercedes have bad engine wiring harnesses. Last, M104 engines have an electronic throttle actuator which is notorious for failing. All three items are expensive to fix.

1992 300E's don't have the dreaded engine wiring harness problem, and also don't have a throttle actuator. Instead, they hava an idle control valve, which are not problematic.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

Suginami,

Thanks for the detailed explanation.

Do you know if these problems with the M104 are the same on a 96 W210 M104?

My 96 has not had a problem with either the wire harness or the head gasket.

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2010 W212 E350 Sport
1996 W210 E320 (220K miles)

1996 E320's don't have bad engine wiring harnesses.

I don't know when the latest / greatest head gasket was finalized. My general feeling is that head gasket failures on W210 chassis 1996-1997 E320's are rarer than on W124 E320's.

Remember that while your engine was no longer used in W210's starting from 1998, it was still in use in the W140 chassis S320's until 1999.

I frankly wouldn't worry about it. M104's are great engines that will surely last as long as you continue to keep maintaing the vehicle.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

That's what I was hoping. Thanks

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2010 W212 E350 Sport
1996 W210 E320 (220K miles)