PeachParts Mercedes-Benz Forum - Gas milageguys, down..down..down the drain..?

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Gas milageguys, down..down..down the drain..?

Hi Guys,

My gas milage went don the drain along with my acceleration..My 95 E420 does not respond fast to kickdowns and accelerates either sluggish or slow depending on how I step on the gas pedal, (hard and fast = slow start, slow and steady = even but slow acceleration, not terribly slow but not good either). One the car is rolling high speeds are not an issue, its just getting to them from a dead stop..However no matter how smooth I try to run it the car is swallowing the gas like nothing..about 12mpg..

I have new OEM caps/rotors, spark plugs and wires and no vacuum leaks..

I got a KS code a long time ago but has not returned since I cleared them 2 months ago..No CEL light on as well..Could this be the EGR, MAF, O2 sensor Throttle actuator or the KS that went kaput but still haven't turned the CEL light on..??

Any help appreciated..this LOW milage is not fun at all..

THxz,

DH

My guess (1st) would be: Take a look at the fuel pressure. If the fuel pump is dogging out (pressure is down from normal), then you're not getting the right amount of fuel when you call for it...it could also be (2nd) a fuel-check-valve or (3rd) the fuel filter.

Those would be the first items I'd have checked out if you can't do them yourself...

Good luck! :thumbsup:

cat could be clogged....

I will check to entire fuel system this week and see where that takes me..how can I check for a backed up cat if I am not getting any CEL light?

DH

Oh, forgot to mention the car has 131K miles..

With the decrease in fuel milage, are you getting a decrease in power?? Other than actually removing the pipe and driving it, I"m not sure how one would check that...

As I live in an area where the Gov doesn't care about cars that age, I'm just going to gut my cat and be done with it...

02 sensor failure is supposed to trip the light, but a faulty 02 reading causes mpg to drop.

Could it be cold weather.My S is burning fuel do too running rich(liked choked) because of cold temps.

How's your exhaust sound? Any louder?

An exhaust leak will also cause that doggish performance.

Quote:

Originally Posted by hudsongua (Post 2645004)

Hi Guys,

My gas mileage went don the drain along with my acceleration..
My 95 E420 does not respond fast to kick-down and accelerates either sluggish or slow depending on how I step on the gas pedal.
Hard and fast = slow start.
Slow and steady = even but slow acceleration, not terribly slow but not good either).
Once the car is rolling high speeds are not an issue, its just getting to them from a dead stop..
However no matter how smooth I try to run it the car is swallowing the gas like nothing..
About 12 mpg..

I have new OEM caps/rotors, spark plugs and wires and no vacuum leaks..

I got a KS code a long time ago but has not returned since I cleared them 2 months ago..
No CEL light on..
Could this be the EGR, MAF, O2 sensor Throttle actuator or the KS that went kaput but still haven't turned the CEL light on..??

Any help appreciated..this LOW mileage is not fun at all..

THxz,

DH

That makes me suspect:

* A plugged catalytic converter.

* One of the two fuel pumps is failing or dead.

.

take out both front o2 sensors and drive it.if plugged cat that will relieve pressure.