TMaguire75

I have a 03 s55 amg with 96k miles on it and the throttle is cutting out in between 2500 and 4500 rpms. It only seems to happen in first gear, and does not happen if I accelerate slowly. There are no codes so the dealer has no idea what it could be. Any ideas would be very helpful. Please let me know if you have any other questions.

rondocap

Can you explain a little bit more how it feels/sounds? It could be an engine misfire, you have 96k miles, getting close to needing to change your spark plugs. The dealer did a diagnostic on it? Usually they can tell if there is a misfire, so it may be something else. Perhaps clogged fuel filter can have this effect?

TMaguire75

Basically when you hit the gas in frist gear pretty hard the throttle cuts out in the mid rpm range and the car like bucks badly like its running out of gas for a second and then continues to accelerate. It seems to only happen in first gear. I have replaced fuel filter, pully's belts, all spark plug wires and spark plugs, ignition coils and there are currently no codes. Due to failer, I also replaced the power steering pump/abc pump. I changed oil and filter and I have replaced the valve covers. I have only had the car 6 months and none of these have fixed the bucking. I have also ran mercedes approved fuel cleaner threw it. The mechanic drove it, says he feels what I am talking about but without a code he is at a loss.Thank you for your help.

Gondon

IC Pump Failing? Do a search on the E55 forums, you guys share the same platform.

rondocap

It doesn't sound like it is this, but just to keep in mind: Also check motor and transmission mounts, they can give you a shake in the car if they are bad or really worn. Do you ever hear a clunk sound? Have you ever replaced them or know when they were done?

TMaguire75

I also replaced the flex discs, transmission mount, changed transmission fluid and filter as well. I bought the motor mounts expecting to replace them but the mechanic said they were good. How long do those usually last on the S55. Thank you guys for offering your help. I have also read about a rev limiter switch in the gear box that sometimes goes bad. Any thoughts on that, and if that were the case shouldn't a code show up? I will take a look at the IC pump forum as well.

rondocap

The transmission and motor mounts can vary, but seem to last 60k or so for the most part. My car has 120k miles, and they were first changed around 60 and I just did them again recently. I do drive it with some spirit though! I am sure if you baby it they can last longer.

But definitely take a look at that IC pump. I am not too familiar with that since my car is the pre 03 model without the supercharger, but it sounds like something that can affect performance on these cars.

TMaguire75

Thank you guys again for your help. I will look at the IC pump, but if that were the problem wouldn't it be an issue is all gears. This is primarily in the low gears, first and second (just noticed it in second yesterday), and it only happens when I am accelerating moderately to heavy (which is why I guess we think it could be the IC pump). However it is not so much a continuous loss of power above a certain the rpm range as it is a hiccup for a second like the car is not getting fuel or air or something that it needs which causes it to buck for a second and then it continues to pull normally. Does this still sound like the IC pump to you guys?