Smash_

Hey guys I have an ML430 and am on the verge of getting rid of it unless I can figure this out. The vehicle has just started getting very bad gas mileage like I can fill up (topped off) and go 20 miles and I'm down a 1/4 tank and this is with normal driving conditions doing the speed limit and not getting on it. This poses a huge problem as I travel 40 miles a day 4 days a week for work. What could be the possible issues? I've done an oil change and changed the air filter about 1k miles ago. just recently the check engine light came on throwing a maf code or vac leak. but the bad gas mileage started long before this. Any help would be greatly appreciated!

MikeC825

I am just slowly working through spark plugs and wires/boots........not sure it will help mileage as they were not great any way.
I started due to misfires and out of the 1st 4 , found 1 bad boot

If your plugs are old..........start there

Smash_

Ok, What about o2 sensor? and what Plugs are recommended?

MikeC825

I have been using autopartswarehouse delivery is quick.
I have 2 O2's ready to go in as soon as the weather here warms up. Tough without a lift. They are keeping my check engine light on.........just hope the cat's are OK

Smash_

I meant could o2 sensors cause the bad gas mileage?

MikeC825

I am sure they can as they change fuel ratios. But I never noticed a major drop. And you get no other engine codes?
The MAF can be cleaned easily if you suspect that. Vac leaks..........that is a tough one as it could be anywhere.

Smash_

yeah The code I get is maf and that came along recently after the bad gas mileage issue...

ldotmurray

Replace the fuel filter if you have not yet done so. A tune up is good (spark plugs and wires). Coolant flush and an oil change help as well. As for the O2 sensors have someone run a diagnostic check on them to see if the fuel trim is within spec. I purchased an Autel scan tool to check these things myself.

Suspension problems can reduce fuel economy as well. Make sure the tie rods, control arms, and all bushings and ball joints are in working order.

Just a few things that come to mind.

*Edit*
Cleaning the MAF sensor may increase fuel consumption.

Smash_

Awesome thanks!

cenzo86

I had a car destroyed by the service manager taking my vehicle for an extended road test. My Jaguar has broadsided by a pickup truck up in Westchester. My dealership was on Long Island. They attempted to repair the vehicle but ended up getting me into a replacement.