1997 E320, 165,000 miles. This car is new to me. I've noticed a couple very minor issues and have done a search - nothing seems to match up. So here goes.

First of all, acceleration doesn't seem linear when flooring the gas. I don't know what other way to describe it. When accelerating lightly or moderately, everything seems fine. But when flooring the gas, such as when passing or entering an on-ramp, it seems like the rise in engine RPMs just isn't very smooth, almost like it's choking very slightly. And I can never get it quite to redline like with my M103; this one just seems to struggle to get way up there. Air and fuel filters are recent, so I don't suspect them.

The car starts every time, but not always easily. When cold, it starts up almost instantaneously. However, when it's hot, it can take 2 or 3 long (5 seconds or more) cranks to get it going. And I think I can smell gas when this is occuring. Could it be a temp sensor? The Check Engine light is not illuminated, and it runs fine once started, so I'm a bit confused.

Overall it runs great, but I know this isn't how it's supposed to be. And I'm hoping the two issues are related. I'm new to the M104 and have not yet learned all the ins and outs.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

The acceleration thing sounds normal for an M104. The engine has variable timing on the intake camshaft and also resonance flaps inside the intake manifold. As these gadgets are adjusted while accelerating the changes in torque produced can be felt as fits & starts in the acceleration rate. I certainly notice this in my M104 engined 124 car, and also recall mention of it in some auto magazine reviews from back when.

Long crank is a tougher diagnosis over the internet. One common service item on the M104 is the fuel pressure regulator. Quick & dirty test is to pull the vacuum line from it and check for presence of gasoline and/or strong odor of fuel.

- JimY

Thanks for the info - I'll do a search on the regulator.

As for the acceleration - what you describe seems to fit my description pretty accurately. All I can say is YUCK! Heavy acceleration is not very smooth at all, nothing like my M103. I had no idea there would be such a night-and-day difference between the two engines. My M103 will sing all the way to redline, whereas the M104 sounds like a blender under the hood and won't hang out in the upper RPMs for very long. And this is improvement?

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

Well, it does have 50HP more than the M103...

Yes, I knew in advance there was 50 more HP, and I eagerly anticipated it. I guess I just wish there was a smooth-revving M103 out there with the extra 50 horses. Maybe I should keep the 300E and do a turbo kit?

The more I compare the two cars, I am beginning to wonder if the W210 shouldn't be the one to get sold...

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

it will willingly go to the red line smoothl yat any time. Particularly likes to do it on this one little curvy hill leading from a four-way stop I traverse frequently. Great sound effects too! I'd say the car's fuel-air mixture may not be regulated properly. Maybe the mass air sensor is suspect? My car has 102K miles on it.

No, I don't think any of those are suspect. There are no codes of any sort and the vehicle recently passed inspection with flying colors. The differences I am observing are in comparison to an M103. Jcyuhn pretty much described it aptly - the irregularity is very subtle, but for someone who has driven thousands of miles in an M103 it is very apparent to me.

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

Have you driven an M103 over the same course? What basis of comparison are you using?

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

but the only thing I have ever had that would wind up like the E320 was a 1993 Ford SHO.

until it grenaded, it would wind up and sound like a
P-51 right up until the moment of failure..then it sounded like a wood chipper trying to eat a steel ingot.

I had a 1989 Taurus SHO. Really interesting, unique, and fun car. Only available with a standard transmission until 1993. Kept it as my daily driver until 1998.

- JimY

Sorry, I would have to disagree with the post on non-linear acceleration being the norm on an M104. If you are getting a slight "choke" or "miss" under hard acceleration, there is a problem somewhere.

Trouble is, there are so many systems to diagnose, and a combination of issues can also contribute. Old vacuum hoses, a cracked intake, wiring harness, plug wires, fuel distributor...the list goes on. It's too expensive to parts swap at this juncture either.

My W124 suffered from some of what you experienced, and it took a top-end rebuild (it was head gasket time anyway) to cure it. I experience none of that anymore when I tromp on the gas pedal!

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

My M104 was as smooth as glass accelerating up to the redline.

Something doesn't sound right.

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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".

I replaced my MAF and the M104 now appears to be working properly. No flat spot or hesitation anymore! However, I should add that it is still a bit notchy and less linear in acceleration vs. the M103. In particular around 3000 RPM it appears there is a marked burst of power. Sort of reminds me of very mild turbolag. I still think the M103 is smoother, but let's face it - time to move on. At least with this M104 working properly now it is much more enjoyable!

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

I experience similar behavior in my 94 E320. Just dropped in new plugs and it still has a 'non-linear' feel. How much was the MAF and did you pop it in yourself? The m104 definetly starts putting out the power around 3400 rpm- from there it rockets to the redline.

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94 E320
71 350SL