formula1gp

Help! I have an 04 S55 having problems with lacking power. It started with conversations about intercooler pump issues. MB dealers changed out pump twice. Car will run good for a day or two, then slowly loose power again. I'm now working with one of the Houston Renntech guys, and have already changed out to a Johnson pump, and a modified thermostat to keep things cool. It ran good for one day.

Just to make sure I'm not crazy, I had the car at a Dyno shop to get some numbers on hp ratings:

before pump changed : 1st run @385hp, 2nd run @273, 3rd run @365 to the rear wheels

2 days after pump change: 1st run @375hp, and 2nd run @352.

For a car rated @493 at the flywheel, even with 15-18% loss, I'm still down 50hp

The car has 45K miles, and still under original factory warranty, no visible signs of burning oil, or rough idle.

I'm fresh out of ideas, anyone has any ideas or have gone thru some of this?

thx in advance.

housclass

wish i could help...but something is very wrong as if you didn't know.

i noticed my car is a monster when cold but once it warms up, it feels like the turbos aren't working...i'm taking it in on monday for a i/c pump change...hope it helps.

hope you find the problem!

john

btw...are you in houston?

formula1gp

yes, the car is in Houston at the moment. I drive it when I'm in town. I know Houston summers and humidity are tough. Still, I have a hard time believing it, giving up 40hp due to 10 -15F degrees shift. I saw no difference between MB dealer changed i/c pump, vs. johnson pump+thermostat. I have however seen some threads concerning new ECU software version flashes, sapping power. Like to find out more about that.

Hazy1

My E55 was feeling very sluggish and dynoed almost exactly the same numbers as your car with nearly the same mileage on my car. My AF ratios did not look right to some of the other forum members. I have K&N air filters and it was suggested that I give them a thorough cleaning. I have not been back to the dyno, but the sluggishness went away completely. If you have factory filters, just change them, or try cleaning if you have reuseable aftermarket ones. It might not be the problem, but is worth a look.

formula1gp

thx for the suggestion. I've already ordered new air filters, and will put them on Monday. I'm also looking in the dirction of maybe dirty fuel filter?? it's cheap, and worth a shot.

housclass

if you could get a data logger and record IAT's it would help...should tell you if it's a fuel, ignition or intercooler problem. just a thought...

john

formula1gp

curious, how did you get AF ratio #s

Hazy1

I asked the guys doing the dyno to plot everything that they could. They didn't have the equip. to track the IAT's, which is what I really wanted to know.

Edit: Here's the graph including the AF ratios on the bottom graph.

GrepAwk

Formula1GP:

Be carefull when installing "Replacment" air filters. Most autoparts stores will try to sell you the wrong part. Or at least they did for my MY'03 S55. I am assuming there was not change for MY'04....

Compare the height of the paper media in the original filters vs. the replacements.

I went to 2 MB dealerships and one on-line guy that tried to sell me air filters that were the right length and width, but were TOO TALL, and the airbox would not fasten down correctly. There were gaps in the seal that would have let dirt bypass the filters. I bet a poor technician would try to mash down on the filter cover to try to make it fit into the airbox.

MANN part number C-3689 = good.
MANN part number C-3698 = bad (too tall).

Don't believe Pep-Boys, Autozone, etc. until you actually compare the ones in your car to the replacements.

formula1gp

thx, I just went to the dealer and gave them my VIN.