Tryan - The M104 3.2 liter engine was a straight six engine from 1993-1995 in the W124 chassis '93 300E (3.2) / '94-'95 E320, from 1996-1997 in the W210 chassis E320, and from 1991-1999 in the W140 chassis S320.

The 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, using a distributor with one coil wire and 6 spark plug wires. This is basically a mechanical injection system with electronic control.

The "modern" 3.2 liter M104 engine was used in all U.S. 1993 and later 300E (3.2)'s, 300CE's, 300E Cabriolet's, 300TE wagon's, and '94-'95 E320's. Note that all 1993 300E / CE / TE's are misbadged as the engine is a 3.2 liter engine. The badging error was corrected starting in all 1994 models, but only the logisticians at Mercedes have the answer for this one.

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 early 3.0 liter 24 valve M104 engines are nice, but the advancement of technology is just so great in the 3.2 liter M104 engine, that if all possible, go with the newer engine.

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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".