m103 tune up?
 

Hello everyone,

Just a quick question. I've got my 190E here with a 3L m103 and it would appear that my fuel economy is tanking. I've got around 170 miles (75% highway, 25% city) and I'm around 1/4 tank.

I've never done a tune up on this 3L motor (installed Feb 08) and I've never done one on the previous 2.6L motor (bought July 06)

What's all included?

Thanks

You should be getting closer to 300 miles to a tank...

plugs, wires, cap, rotor, oil, filter, fuel filter, air filter.

Is your abs light coming on occasionally? I had a problem with my ovp, and it made a huge difference on fuel economy..

What kind of mileage were you getting before?

Nope no abs light coming on. I repaired the OVP a few months ago, took it apart cleaned and resoldered all the components.

plugs-i dont know when they were last changed

wires-same (but I have a spare Bosch set that I just installed on my 2.6 before it died)

rotor-same with plugs

oil/oil filter is due in around 1k miles

fuel filter was last changed around less than 20k ago

air filter was changed hm dont recall when..


Last recalled mileage on this motor was approx 21mpg, same driving conditions

Now your getting close to 12 mpg.. It might be something a bit more than a tune up..

Id start with the tune up, and see what happens from there..

Well it was was a rough guess with the numbers, I havent been able to refil the tank and calculate proper mpg.

Alternatively it could be the sender unit going bad. I know this is the case in my 300SD. However I suspect that not to be the problem here.

I was having a huge problem with fuel economy on my 300TE and I replaced almost everything in the fuel and ignition system and it ended up that my EHA was killing it. I jumped from 13 to 17 with its replacement. I still think I could be doing better though...

Id start with the tune up first, then calculate mileage. With that much highway driving, you should easily get 300-325 miles at the point when your reserve light turns on.

I do 90% city driving and get around 275 miles to a tank.

What is a "EHA"?

I felt curious today and decided to check my duty cycle at idle:

Battery Voltage was 14.23v
Low Voltage @ x11/3 was 10.99
High Votlage @ x11/3 was 11.49

So, duty cycle was between 23-29%.

I adjusted this a few months ago to be back near 40-45%

You think I should perform a tune-up first then adjust this or vice versa?

I also believe my EHA is tweaked a bit high, I thought about removing it and lowering it a bit and seeing if that brought the mixture back inline...

Thoughts?

I don't know how old the motor you put in there is, but M103 motors get leaky valve stem seals after about 100K miles, and I have discovered that the oil leaking into the cylinders will foul out the plugs about every 3-4K miles in my 300SE. Taking them out and cleaning and gapping them gives me back power and economy.

These motors are very sensitive to the condition of the ignition systems so check that.

You certainly want to get your duty cycle sorted too. If you set it correctly a while back, it might be an indication that the 02 sensor is on its way out, or you've developed a vacuum leak.

The motor has just around 90k on it now.

The O2 sensor has maybe less than 5-7k on it now.

I havent done a tune-up yet since I've had this motor. So it might be time for that.

I havent pulled the plugs to look at them either. I'll post pics sometime this week, since I've no clue what I'm looking at.

Every 3-4k? Mine would foul every 400 miles! :eek: I had the stem seals done and now mine uses 0 oil between 4k changes....and runs perfect. It used to drink a quart or more every 500 miles.

Yeah, mine hasn't gotten quite that bad yet....... I go through a bit of oil, but a lot of it is just the under-chassis lubrication system.:rolleyes:

Thankfully mine is pretty much dry....only an ever so slight leak at the front timing cover area.....but it is far too minor to worry about.

You should have seen the old valve stem seals....they were hard as rock!

I have a slight oil leak at my front timing cover, typical of m103's. Nothing else.

As of last oil change I didnt notice any oil consumption, level is in the middle of the notches on the stick currently.

edit: Checked today oil is still in the middle of the notches.

Furthermore: I've realigned my air fuel mixture.

I do have one question, based on the formula from http://landiss.com/mixture.htm

DC = (1 - Pin3/Battery )* 100,
are percentages below 50 considered to be "running rich" ?
and percentages above 50 considered to be "running lean" ?