Poor Fuel mileage in 190 2.3
 

Having just recently purchased my first Mercedes, 1986 190e 2.3, I was not really sure of what kind of gas mileage to expect. After reading numerous posts on this board, I feel that my mileage is kind of low. Most of my driving is in town, stop and go. Very little open road 55+mph driving, more like 25-35. The best gas mileage that I have been able to get is about 14mpg. I do run 93 octane fuel. I kind of drive with a heavy foot at times, but I was hoping for a little better mpg. My Tahoe was driven the same way, and got the same gas mileage as I get now! The car has 119,000 miles on it. The cap and rotor were recently changed, the plug wires look fairly new, the platinum plugs don't look that bad, clean air filter. I feel like I have checked most of the possible culprits, and I am still at a loss of why the gas mileage is so low. On a possibly related note, when I got the car, it was a very hard cold start until I figured out the fuse on the OVP relay was blown, I replaced the fuse and it starts easier now, but still has a rough idle until it hits 80 celsius. I apologize for the lengthy message, but I am really hoping that someone could point me in the right direction of what I need to check next. Being new to the Mercedes way of doing things, I have checked all that I know how to do.

Ditch the platinum Plugs and use regular copper bosch plugs and see what happens;)

Thanks, I will change the plugs tonight, fill the tank, and see what happens. :)

14 mpg sounds very low. You should be over 20mpg. If the car runs ok and the plugs look ok, would suspect a possible fuel leak or possibly leaking injector or cold start injector. You may have a hang up in the chassis (dragging brakes etc).
One other thing that comes to mind is the trip meter could be innaccurate. They do fail regularly. Verify this buy checking it vs the odometer. Let us know what happens.

Check your tire pressures. Also check the tires for an even wear pattern... possibly rotate them?

Try checking the Oxygen sensor in the exhaust system. I had a similar problem on my 1986 190-E 2.3-16, a grey market car so some things may be different, and it turned out to be the Oxygen sensor. Apparently when one of the inputs into the computer for emissions goes out, the computer shuts down and the car runs in a purely mechanical mode to make sure you do not get stranded. In this mode the mileage can be really poor. That was the explanation I got, and when the sensor was replaced the car ran great again. I still only get 27 mpg combined driving, but a buddy of mine with a car like yours, and a 5-speed, routinely gets over 30 mpg and he is an aggressive driver. A lot of his driving is on the highway, but still that is way better than 14 mpg. Good Luck. Jim

Thanks to all that have replied! I changed the plugs last night, and as I do once a month, I checked the air pressure in the tires(set to factory #). If the mileage does not improve after the plug change, I will try the O2 sensor. I have the service CD, does it describe the best method for checking the o2 sensor? I really enjoy the car so far, albeit I have already fixed numerous small things, I am certainly sold on the Mercedes brand now, If a 16 year old "baby" benz drive as well as this, then I can't wait until it is time to buy a new one for the wife next year. Nothing I have ever owned has felt so solid after 119,000 miles. Now I can see why people become "mercedes people". This car will be a dream to drive after all of the small "bugs" get worked out.:) :cool:

Copper plugs rule!!
 

:D Just an update, I switched to copper plugs, having done so, the gas mileage has been drastically improved. I haven't yet gone through a full tank of gas to figure an exact number, but according to my trip odometer, and the gas guage I am probably getting at least 20mpg now. WOW hard to believe that spending $6.00 on plugs can make this kind of difference. Many thanks to "yal" that suggested the change, I never would have thought to change back to copper from platinum. Once the tank of gas is gone, I will recheck the numbers, but so far this seems like the fix. THANKS!!

The switch from Pt plugs should NOT make this big difference in mileage. I suspect there is some other underlying problem that caused the Pt plugs to eventually start misfiring, and you will again have the problem after the new plugs have accumulated some miles. Perhaps checking for error codes would be a good idea.

Steve

I don't think this model comes with error codes.

If I faced a similar situation of high fuel consumption, I would race to have the engine fine tuned.

I'm not sure if this matters, but the Platinums looked okay, color wise. When comparing them to a "spark plug t-shooter" photo, the coloring looked fine, not too lean, not too rich, just worn. Having just bought the car, I do not know when they were installed. By tuning the engine, what exactly do I need to do. I thought the timing was set, and could not be changed. Air/fuel mixture I guess could be checked. But with the fuel mileage that I am getting now, I am almost afraid to change anything. But in an effort to keep the MPG up what should I look for now? Not sure if it is relelvant, but the car does hesitate upon taking off, until it is warmed up 60-80 c. Perhaps cold start valve leaking and fouling plugs?:confused:

"190guy" stick with the copper plugs and watch the fuel consumption, If you see a drop then start looking at other things. Contrary to popular believe platinum plugs are not all they are cracked up to be on an older benz engine. If you have a variably timed engine then they work ok. But our pre 90 engines just detest them. I have heard more stories against them than I have for them on these engines. Also change your OVP its good insurance to do this. Finally check the condition of your fuel pump relay (the rectangle box next to the OVP) and do a fuel pump pressure test. Your temperature sensor is also crucial to start up. Do a search on all these things I have mentioned and you'll get lots of info for you to check.
Of course non of this advice can substitute taking the car to someone you trust who knows them well;)

Yal,(and everyone else:)

Thanks for the advice on what to check next. Man this forum is a goldmine for info. I think I will go ahead and change the OVP, when I got the car the fuse was blown and the car would hardly start at all when cold. Cheap insurance to replace now, I think. What doesn't the OVP affect, it seems like it has a hand in everything. One other ? , what is on the far left in the same area as the OVP and KLIMA, and fuel pump relay, I am talking about the thing that has a heat guard(?) in front of it. I opened my hood the other night in the dark, and I saw what looked like a glowing spring, it was putting of quite a bit of heat when the car was running, as soon as I turned the car off, it stopped glowing. Is this some sort of voltage regulator or what? Sorry to get off the thread topic:rolleyes: But I am wondering what in the heck this thing is.