HELP - Sudden MPG loss


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I am 900 miles from home on a weekend and need help, please. I have a 2004 140" SHC with a brand new US rebuilt engine. The engine now has about 4000 miles on it, almost all driven by me with TLC. Up until yesterday I have been averaging about 25mpg (based on both Scan Gauge and hand calculated.) Driving in a very heavy rain and wind storm my mpg according to the SG dropped drastically. At first I thought it was the very strong winds (not so fun!) The tank was just below 1/2 and everything seemed to be running fine. I drove until the tank was at about 1/4 then filled up. The SG showed 19.1 and calculated showed 17.1 mpg; SG had been almost identical up until this point; the SG fuel consumed (tank fill-up gallons) was too low, also.

Now I have driven just under 300 miles since the last fill up and SG claims 15.1 mpg and calculated is still at about 17.0 mpg. There is no obvious problems. The vehicle sat overnight and there is no visible leaks on the ground or on the vehicle. I can't tell but I think the turbo is running most of the time as I hear the whine, but then again, I did not pay enough attention before to properly gauge but I think the whine used to only kick in occasionally. There is no loss of power. The vehicle appears to be running just fine and if I did not have the SG and were not so 'retentive' about calculating mpg with every fill-up I would not notice a problem.

Brakes are not dragging to the best of my knowledge because I can put the vehicle in neutral and push it around easily by myself (even slightly up hill). I checked the air filter and it is dry and very clean. Oil level is good and oil looks quite clean for 4000 miles. I wish I paid more attention to what RPMs were associated with what speeds so I could get an idea if I am actually in the proper gear but the transmission appears to be in 5th as it indicates. I am getting about 2400 at 65mph - if I remember properly from last night. (I camped out at a truck stop, hoping to learn more.) There are no engine codes showing and no alarms, indicators, etc. All around the engine compartment it is still very clean and dry after the rebuild install - the dealer did a nice job at that! I will disconnect the Espar and see if that makes an difference but I don't really suspect that little gadget. If I can find a fuel filter on a Sunday I'll change that (I am opening to trying anything that I have the tools and resources to a do on the road.)

When the engine was replaced the transmission was serviced (new fluid, new filters); the differential fluid was replaced; and the front brakes replaced and serviced. There was additional work done, too but all superficial, nothing that would indicate a relationship here.

Since I am 900 miles from home I don't want to do more harm by driving the vehicle if something serious is wrong but I also don't have the time to just sit around (I don't want to get fired for not showing up for work!)

Please (again), if anyone has any ideas that I can try, let me know ASAP. Thank you very much for any help and consideration.
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New member
Hopefully someone else may have the answers you need, but my advice is to locate the nearest Sprinter dealer. Drive under 55. Explain to them your unusual fuel mileage, and hopefully they will solve the problem.

It may be something as simple as a bad mass airflow sensor......


Not Suitable w/220v Gen
I agree with Suba: Have it evaluated with the proper dealership tools since you're so far from home. This would help rule out nefarious conditions that may worsen over time; you'd at least be able to say you had it evaluated if something catastrophic happens.

One question I'd like to ask of the readers: can bad fuel manifest itself solely as reduced efficiency/lower MPG and w/o any other noticeable consequences or does bad fuel always *have* to make the engine run rough, stall etc?



New member
One question I'd like to ask of the readers: can bad fuel manifest itself solely as reduced efficiency/lower MPG and w/o any other noticeable consequences or does bad fuel always *have* to make the engine run rough, stall etc-Jon

The way in which your question is asked indicates you already know the answer (!) As you undoubtedly suspect, I am not a mechanic. I've tried to reason my way through with respect to Sprinters the best way I know how. From my limited expertise, I believe bad fuel ( low grade fuel with low cetane ) can harm our high tech engines, yet an engine may not exhibit any outward signs that would indicate there is a problem until it is far too late. Don't make me explain why I feel this way. I try to use fuel from reputable stations.

Conversely, I feel that modern ultra low sulfur fuels lack proper lubricating qualities. My opinion is strictly non empirically based. On every fill up I add a concoction of Lucas Upper Cylinder Lube, Non Synthetic Ashless Two Cycle Oil, Power Services for cetane, and Marvelous Mystery Oil for good measure. In all I dump two cups of stuff in my tank with every fill up. I think I'm aiding in the longevity of my engine. I guess time will tell, but my engine seems VERY happy (!)



New member
Suba, et. al.,

Thanks for the comments, however, being so far from anywhere in New Mexico I don't have a Sprinter nor a Freightliner dealership near at hand. Reading more posts and other information online this morning, before Suba's reply, I found a reference to MAF sensors and a copy of a dealership memo saying that if the MAF is suspect or in need of 'resetting' then disconnect the sensor wire and start the Sprinter again; if all runs properly then the sensor is probably the culprit but that running the engine long enough to allow the computer to do something ? then re-connecting the MAF sensor may actually reset it to normal.

Ok, so I did as suggested in the memo as follows: 1) disconnected MAF. 2) Restarted engine and it appeared to run just fine. 3) I drove down the road a few miles. Amazingly, SG MPG was back to over 26 but the vehicle was wimpy as it was not kicking in the turbo - ok with me as this told me one of several things and at least I know know what it is not. I stopped, plugged back in the MAF then continued down the road and now MPG is averaging around 25 on Scan Gauge (SG) and the tank is dropping at the appropriate rate (I know on average 3/4= 212miles, 1/2=360 miles and 1/4 = 500 miles -- I told everyone I was 'retentive'!) and the turbo appears to be functioning properly.

I will stop in Dallas tonight and in the morning go to a dealership there. At this time I only plan to buy a new MAF sensor to have on hand if the next tank averages out at above 24mpg and continue homeward to leave the vehicle at a dealership in Houston for servicing. If it is lower than 24 I will see about getting a service appointment and leaving the vehicle and flying home to return later.

I have a great dislike for dealerships and avoid them like liver and onions.


New member
Re: HELP - Sudden MPG loss - MAF issue

I should have called this thread 'MAF - Sudden MPG loss!' Apparently either water made its way past the air filter or condensation and dirt affected the MAF but the problem was the MAF causing faulty sensor readings being sent to the engine computer. When I took the MAF out on the road and cleaned it the best I could and then 'reset' the senor by running the engine for a short time with the MAF disconnected this solved the problem.

The vehicle was in the shop at Dallas Chrysler Dodge Jeep for over two hours. The service tech did the full DRBII monitoring, checked vacuum and air pressures at various places, removed MAF and air filter for inspection and tested/inspected other things, according to the very long report he wrote, before taking the vehicle for a test drive. He cleared the two codes of p0100 and p0102, both MAF, but he could not duplicate the problem I had before the reset.

Since I cleaned and reset the MAF somewhat as per the Service Bulletin I found online, I am happy with Dallas Dodge's work and both Suba and I can relax a bit about the vehicle.

Now, for the best part!!! Dallas Dodge did not charge me for any of the testing/work despite having a signed form saying they would charge $103.97 per hour for even touching the vehicle (hooking up DRBII reader, diagnostics, etc.) Since I travel through Dallas on a regular basis I will have no problem buying parts from them when possible as I respect a company that will treat you fairly on issues like this.


New member
I've noticed my MPG has dropped signficantly since I purchased the vehicle. Since I purchased it, I've had to replace the turbo for blowing oil and all the fuel lines because of cracking. I think I'll need to clean or replace the MAF, but I'm not sure what I'm looking for. Mine is a 2002 OM-612. I see the MAF on the turbo intake from the air filter. Is there another one?

Does anyone have a procedure for cleaning the MAF?

Also, I checked eBay for Sprinter MAF and they range in price from $52 to $300. :idunno: Can anyone tell me which one I should go with if I end up having to replace it?

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