atxmike63

okay, had to re-register since it has been a while... i have an 01 c240. my milage during city milage has dropped 4mpg, my mpg at freeway speeds is great (33mpg). when i accelerate under loan in gears 4, 5, and six it is sluggish and i note some surging at cruisin rpms {2500-3000), and it takes like forever to punch up in the lower gears from starting under loads. Manual trans guys! 187K miles. Loads of recent repair making up for the age, all new rubber hoses, new O2 sensors with the left bank upper left to replace, new bottom o-ring rubber gaskets on all injectors, replaced the air manifold gaskets and valve cover gaskets. Zero codes!!! What could cause mild surging, poor load acceleration, and lower city mpg???? No cat rattle or rotten egg smell. Has me baffled! I have the dash command app and the fuel rail pressure seems to be bouncing from negative to positive in even numbers and intervals. fuel pump replaced two years ago.... i am at a loss. I don't want to just throw cats, coils, and injectors at it - I just spent $2k refreshing a lot of worn out but not broken parts (well, except for one valve hose that was not shown in the parts list at Autohauz - man, that thing was TOAST)

neurodave

You're in the same boat as me brother. On the highway she is excellent. I can squeeze out over 400 miles a tank. In the city, she's like driving through quick sand. Horrible MPG, and the overall feel is sluggish. I've had people suggest either the fuel pump, fuel filter or maybe even the cats are on their last leg. All assumptions....

If you find out, please share it, as will I if I do!

atxmike63

so i popped by a reputable muffler shop here in austin. he stated that you would know when there is a bad cat on a w203 - it would rattle like a **** and you would have acceleration problems in neutral just revving the engine. i am beginning to suspect i have an injector with a poor spray pattern that clears up under heavy acceleration (otherwise it would not accelerate perfectly from 3500 to 6000 rpm like it does in first, second, and third).

neurodave

Keep us posted! I'll do the same, just haven't put too much effort into it just yet.

KSKarl

Since the engine runs well at highway speed, but not low speed, you don't have a fuel problem. More likely a vacuum leak.

Olivier480

My c230 shakes soon as I hit 60 mph or higher on the highway and my check engine light keeps coming on. The shop said it was the camshaft sensors but it was replaced, yet I'm still having the same problem..and my gas mileage is awful on the highway.

atxmike63

KSK, i just replaced all of the vacuum hoses under the hood. i will retrace my steps and see if i missed one or didnt put one on correctly.

KSKarl

Mike, you might also check the hose from the MAF to throttle. That's another sneaky place for unmetered air to get in.

ildd

Tell me your secret... I'd love to get 33mpg highway.

atxmike63

live in Texas where it is completly flat. some poor guy in Colorado has the other side of the milage spectrum!

atxmike63

oh, duh...i see you live in Tx. as well! Overall is 22 (down from 25). i guess you can say i am hyper about routine maintenance. i just went thru a major refresh under the hood, all new vacuum lines replaced, new plugs and wires, replaced the air intake and valve gaskets, replaced everything in the cooling system, new front and rear shocks (Billstein) and new rotors and ceramic pads.

that milage is at 70mph, meaning a clear freeway - NOT commute milage.

atxmike63

so, replacing the four coil packs that were origonal helped a LOT. smoothed out acceleration and city milage is improved. it's not as good as new, but I can live with what i have. I broke my rule and bought non-oem packs. Bosch were $55 each, I got four for $80 delivered.

gqlhonourbv

I'll do the same, just haven't put too much effort into it just yet.