Urk! If that's the original fuel filter you're running on borrowed time and should be on the side of the road any week now. Lots of posts on this. Look for "W211 E55 fuel pump relay and fuse maintenance" and "fuel pump adapter cable" under advanced search. And there are several variations of the fuel filters and pumps and not all are compatible. The latest fuel filter and fuel pumps require adapter cables for each to work with the stock electrical harness. Search and read!

Fuel pressure should be about 80 psi.

Example here:
https://mbworld.org/forums/w211-amg/...ml#post7284407

Posting your location would also help as there are different part numbers for the filter depending upon which region of the world in which you are located. EDIT: I just figured out from where you are. Different part numbers in Australia but the info about the relay still applies.

 

My guess is a hiccup at SC pulley engagement. My car got one when I put a eurocharged tune on it. (Had a smaller SC pulley already I had been driving around with stock tune and no hiccup).

I asked them to fix it when I had the tune adjusted for headers, but no luck. Been thinking about getting a Tony Leshaw tune. Every one seems to love his customer service.

 

I have a similar flat spot/ hesitation in that RPM range. No idea if my fuel filters were ever replaced (at 99K now) and I am extremely confused on what is actually needed to do the filter swap.

When I look at the new fuel system part numbers I find these as the most up to date:
211-470-00-00 Fuel Delivery Module (dual pumps)
211-470-64-94 Tank Inner Module (actually filter/regulator)
211-471-05-79 Fuel Sender Seal x 2
211-440-05-07 Cable Harness adapter for filter/regulator
211-540-07-00 adapter cable to fuel pumps

But I also see confusion about the new dual pumps providing too little pressure? No fuel smell either so maybe my pumps were replaced before, and I just do know about it. There have been posts about testing the amp draw on the pumps, but never saw a write up on how to test that, but that would defiantly help.

I too have a EC tune and pulley, but had the hesitation before the tune and pulley as well. My car is a US spec '06.

 

Any way you can place an Air/Fuel meter on the car? I found that flat spots (from my days of tuning aftermarket ECU's in forced induction Miatas) were usually caused by a lean condition. Lean feels like a "bog" as when pressing the throttle the engine just seems to lose power (hope that makes sense). Alternatively, it could be going pig rich but that is unlikely as it only occurs for a short interval of a few hundred rpm if I read your post correctly.

 

Sorry guys, is it common for a clogged filter or fuel system issue to begin to affect normal driving before WOT driving? As the OP described accelerating "as you would in traffic or off a light" I doubt this is an under boost issue, I would guess that if your fuel system was at the point that closed loop driving was getting lean enough to cause noticeable issues, the first time you went WOT(open loop) you would probably melt something.

Bbirdwell's got much more experience with the platform with me so pls correct me if I'm wrong, however I would not go chasing down fuel system components just yet. I still think it would be better to look towards SC clutch engagement or tune issue.

I would take off the SC belt for a day or two and and see if the hiccup is gone before you start spending money on anything. (the recommendation for a wideband is always good though, regardless of the situation )

 

 

The SC engagement is based off of throttle position and RPM. So as you beging to accelerate it will usually pop in very early unless you are super gentle with the throttle. Mine usually happens when casually accelerating from a stop. Always under 2K rpms unless I focus on giving only very slight throttle, or hit it a little more agressivly then it engages right away and have no issue

 

The E55 fuel pumps are all or nothing; should be around 80 psi at idle (FWIW, when I pulled my fuel filter at 90K miles the pressure was around 72 psi). If one pump is failing/failed, or wired incorrectly, you'll see the fuel pressure fall off at higher rpms at WOT (BoostedAero or Seanol had a post on this). The W211 E63 uses what appear to be PWM controllers.

I would guess something to do with the tune. It's easy to tune for big horsepower at WOT but a PITA to get all RPM and MAP ranges to work well with timing, target air/fuel mixture, volumetric efficiency, mixture enrichment depending upon coolant temp, air temp, throttle position rate-of-change, etc, etc, ad infinitum. Changing the intake or exhaust will have an effect that must be accounted for. Heck, pulling the Helmholtz resonator off an NA Miata intake has a discernible effect on the torque at particular rpm ranges. I don't even want to begin to consider the complexity of the Mercedes sensors that provide input to the engine control unit.

Best bet is to record data from as many sensors as you can and look for the one or two that look different as you go through the RPM range in question while comparing it to another RPM range where all works well; Be easier if you can do so by recording data at several different MAP levels across the RPM range (i.e. 70 kPa, 90 kPa, 110 kPa, etc). RPM, throttle position, air/fuel mixture, mixture feedback loop, O2 sensor data, MAP blips, etc. It's a process. Just display your data and step back and forth the RPM range in question. You may be able to quickly narrow it down to a few areas of interest and, if it does appear to be something in the tune, e.g. air/fuel goes lean over a 200 rpm range, you should be able to discuss it with the person who programmed that tune and have it modified for your car.

Best of luck and keep posting what you find.

 

I'm not sure what you mean by "locked" but no you can't just swing in to a shop and have them make a tune for you, whether you have a eurocharged tune or if it's stock. The people that have the ability to tune mercedes vehicles are few and far between. Most of which you will find right here on the forum with a little searching.... and if you don't find them on this forum, you probably shouldn't let them touch your car. Mercedes ECUs are fickle beasts, they are not like an LS1 that you can toss into a dime a dozen shop and get tuned up.

I'm telling you, before you start paying for anything or hunting anything down, pull your SC belt off and drive for a bit, see if the hiccup is gone. It takes less than 5 minutes and it's free to check.