JesusL

Hello,

So I finally purchased my first MB about two weeks ago. It's a one-owner 2003 E320 with 120k miles on it. Bought it from an older gentleman who did all scheduled maintenance and kept it garaged. Car came with 2 original keys, original sticker, original manuals, and a folder full of service bills. Interior is in EXCELLENT condition and exterior has some minor cosmetic issues which is understandable. So car is in great shape all around. No check engine light or malfunction of any type. Engine starts perfect and runs totally smooth at idle with no rattling or ticking sounds, only a very very light hissing sound, but otherwise a very quiet engine. Ride, city or highway, is very typical of a MB, firm, comfortable, and solid even at its age. I really like the car and got a great deal on it so I am happy. Now, the only thing I notice is that acceleration is a bit poor or sluggish. It does not hesitate or jerk, but when I press the pedal the car feels heavy and picks up speed rather slowly. When the light turns green and I go, the car behind me is usually in my back and the cars to my sides just fly by. The other thing is that there is a very light tapping sound when I accelerate which usually disappears as speed is gained, or if I take my foot off the pedal. Going uphill while picking up speed, the sound is more noticeable but again disappears when speed is reached and there is no more load on the engine. Fuel economy seems to be fine, in fact I am rather impressed in that sense. The only thing I have done is put a bottle of Techron in the tank and I think it did help some, but I would like to get more information before deciding what to do next.

Any expert advice or comments are greatly appreciated.

Regards, JL

Elkagu

How did you go about it? I'm having exact issue right now with thesame model of urs.

F1Fan

I have an 05 E320, also had what felt like a sluggish car. First started with the basics. Things like engine air filter, spark plugs, oil change etc. Once those were in a known good condtion, and with little improvement, started to look at what else could cause slow response. Came down to the O2 sensors and the catalytic converter. Replacing all of the O2 sensors and wow the engine came back to life. I had alsl replaced one of the catalytic converters because it was cracked, but didn't seem to wake up the engine like new O2 sensors did. I had an OBD2 scanner to show me live data of the O2 sensor before and after replacing them. Functionally, the old ones were still giving readings, but there was a difference. The newer ones seem to respond faster. I think over time/wear/age the old O2 sensors get lazy and do not respond as quick as a new sensor. Just sharing my experience with you. Your situation may be different. If you do decide to replace the O2 sensors, use only Bosch O2 sensors. Bosch O2 sensors come with anti-seize already on the threads. There are reports of non-Bosch O2 sensors not working properly. You can easily reach all of them with basic tools if you can get the car lifted off the ground safely (Do not use the emergency jack in the car). I bought an O2 sensor socket but it was not necessary.

Having said that, I assume there are other issues with your W211 with M112 engine. Things like oil leaks, engine mounts, secondary air injection system, airmatic (if equipped), suspension noises/clunks, SBC eating rear brake pads, etc. Engine mounts, amazing how it makes the car feel faster. Old torn mounts suck the life out of the car moving. Having said that, it is a very easy car to work on. FCPEuro's lifetime warranty is a blessing. Great car, just needs a little TLC to keep it good form.

tjts1

Check your fuel pressure at the rail. Should be 53-56psi and never drop when you rev it.