Poor mpg and possible auto gearbox problems

[E280Tim]

Hi everyone,

I'm new to the forum having only owned my E280cdi 2009 estate for a couple of months.

On the whole I'm pretty happy with the car but it does have a couple of issues.

Firstly. Although it has full MB dealer history it had only had 1 gearbox service done at 45K it's now done 110k. I've now had a gearbox service done at my local Merc indie but it hasn't cured the rather slushy feel of the gears also when reverse is engaged it takes a couple of seconds to start moving. If parked on a hill the car will roll forward when you're trying to reverse.

Secondly. I'm less than impressed by the fuel economy. 35-36mpg on the motorway at a steady 75mph over 100miles or so. I've got the tyres at 38psi all round and it's only been filled with BP ultimate fuel since I've had it.

The only fault code that shows is P2A00 Bank 1 Sensor 1 but my indie tells me this is a common code and not to worry because the car doesn't have that sensor so OBC is looking for a sensor that doesn't exist.

Also the exhaust tail pipes are really sooty and I mean really sooty

Any help on these issues would be gratefully received

 

[bob6600]

It seems to be an O2 sensor fault? Although by googling the code, it doesn't seem to effect the running of the car.

Perhaps an injector leak off or STAR session to check tolerances. EGR could probably do with a clean too. Have you taken it for a good hard drive?

 

[E280Tim]

Hi bob6600,

Just driven from Hertfordshire to Scotland. Several random resets of of mpg reading on the dash every 100 miles or so.

Occasionally saw 41 or 42 if going downhill when reset was done but mpg quickly dropped again to 35-36.

I have given it quick a serious Italian tune up but that hasn't made any real difference.

The best mpg I've seen was 45ish on the M25 at about 75mph just after a very spirited run up the A1 then hit cruise control on the motorway. I was very happy with that kind of mpg and thought maybe it had just needed a good blast, but sadly next day back to the usual poor mpg.

I have read that putting a higher temp thermostat might help? Car seems to run at 88-90c which I assume is correct but it did seem to give much better mpg for about 20 miles straight after a good thrashing?

 

[Chicster]

Regarding your gearbox problem...just had my 220 c class in for a service at 49k the technician informed me that there is a 70k gearbox service which could be required sooner if I experienced the reverse gear problem.It includes some new advanced oil.....hope that helps

 

[E280Tim]

Hi Chicster,

Did they give you any idea what sort of problem to expect?

 

[Mr Filipov]

The age old fuel consumtion problem. I would say mid to high 30s is where it is at. At 80ish in my previous CLS 320CDI I would only see about 35-36, and it does not weigh any more than the tank that is the e class estate. Very much see the same figures in my 2011 E350 CDI at those speeds (give maybe another 3-4mpg). With this one I find the sweet spot to be 70mph. Returns over 50. However the official figures are only good for relative comparison. Tests they do are not realistic. The extra urban they merely hit 50mph and not for long at that.

 

[BlackC55]

The o2 sensor fault will cause poor economy. It needs to be replaced. Your garage is telling you porkies. The O2 values are essential for economy.

The gear engagement pause is usually cured by a gearbox software update. The lack of hold on a hill in D is not an issue. You have a brake hold function if you depress the brake pedal firmly when stationary.

 

[E280Tim]

Thanks BlackC55,

I am inclined to agree with you re the O2 sensor. I'm a bit surprised that the garage would say that it didn't have the sensor that the code refers to but maybe I miss understood (it must have O2 sensor/s). I'll go and see them again and discuss.

As for the gearbox. Would you recommend a gearbox specialist or back to the Merc indie (the one who said I didn't have that O2 sensor). I've always been happy with the work they have done on my Sprinter and my previous car (530d BMW).

 

[Mr Filipov]

The o2 sensor fault will cause poor economy. It needs to be replaced. Your garage is telling you porkies. The O2 values are essential for economy.

The gear engagement pause is usually cured by a gearbox software update. The lack of hold on a hill in D is not an issue. You have a brake hold function if you depress the brake pedal firmly when stationary.

I will begin with saying that I am not suggesting you are wrong in any way. In my cls I was driving around with a duff o2 and maf sensor for quote a few months, and after replacing them it didn't seem to make that much of a difference. From what I was told (again not set in stone) the car only goes back to default values when these parts fail. To me that sounds like, if you have a car that runs very close to true when full working order is present for parts, going to default should not make much of a difference. O2 sensors are more for emissions with pre and post cat to enrich or make the mixture lean, but a default setting is present of course. Never failed my MOT with faulty sensors. A faulty maf sensor would make more of a difference to economy as it measures the amount of air going in. The difference I saw, if any, with the parts working was probably 2mpg max.

 

[BlackC55]

Thanks BlackC55,

I am inclined to agree with you re the O2 sensor. I'm a bit surprised that the garage would say that it didn't have the sensor that the code refers to but maybe I miss understood (it must have O2 sensor/s). I'll go and see them again and discuss.

As for the gearbox. Would you recommend a gearbox specialist or back to the Merc indie (the one who said I didn't have that O2 sensor). I've always been happy with the work they have done on my Sprinter and my previous car (530d BMW).

The gearbox will need plugging into a genuine MB Star system. Your indie should have one. I do.

 

[BlackC55]

I will begin with saying that I am not suggesting you are wrong in any way. In my cls I was driving around with a duff o2 and maf sensor for quote a few months, and after replacing them it didn't seem to make that much of a difference. From what I was told (again not set in stone) the car only goes back to default values when these parts fail. To me that sounds like, if you have a car that runs very close to true when full working order is present for parts, going to default should not make much of a difference. O2 sensors are more for emissions with pre and post cat to enrich or make the mixture lean, but a default setting is present of course. Never failed my MOT with faulty sensors. A faulty maf sensor would make more of a difference to economy as it measures the amount of air going in. The difference I saw, if any, with the parts working was probably 2mpg max.

Was the sensor a genuine one?

Were all the adaptations re-set afterwards? Essential when a component like that is replaced.

 

[E280Tim]

Hi BlackC55

No sensors have been replaced yet. The OBD is showing a code P2A00 Circuit range / performance bank 1 sensor 1.

Indie said ignore this code as it referred to a sensor that wasn't fitted to this car, I thought that a bit strange.

They also did a gearbox service should they have updated the software at the same time, I had discussed the fact that the box was slow to engage in reverse

 

[Mr Filipov]

Was the sensor a genuine one?

Were all the adaptations re-set afterwards? Essential when a component like that is replaced.

Yea did the whole shabang on the old car. Its gone now but not before sinking 3 and a half grands worth of bits and bobs. Effectively fixed it up and left for someone else to enjoy lol
The last straw for me was the intercooler pipe just before christmas haha

 

[E280Tim]

Latest update on poor mpg...

450 mile drive back from Scotland to Herts. Reset mpg at the start and averaged 36.7mpg traffic was light, only a few minutes of slow moving traffic around Manchester and cruised at between 70-80mph.. Really disappointed

Engine temp seems to be running at 88c but does drop a to 86c or 87c every so often is that enough of a drop to give such poor mpg?

Should I look at a 92c thermostat?

 

[E280Tim]

I should add that the O2 sensor code hasn't come back after a weeks and over 1000miles

 

[LvR]

IMO Star is the only answer as has already been said.

With the Star connected take it for a typical drive and monitor real time data on the pre cat O2 waveform - also pay particular attention to the values of short term and long term fuel trims - if the ECU is in proper control of the engine you should see short term values fluctuating around 0 by a few % (average should be close to 0) and long term should be a constant value typically under 10% if the engine is in good condition.

Report those ST and LT values here as well as a typical O2 graph you see (somebody can comment) - if they are behaving normally then high fuel consumption is not caused by the ECU, then Star can also start telling you all about the gearbox while driving and monitoring real time data

Engine temp seems to be running at 88c but does drop a to 86c or 87c every so often is that enough of a drop to give such poor mpg?

Should I look at a 92c thermostat?

Those temps are quite acceptable imo and no don’t go fitting a 92C stat. With ambient around 18C I would guess that operating temp should be reached within about 2-5 km normal driving - does that happen?

 

[bob6600]

^^and whilst connected get the injector tolerances checked or get a leak off test done

 

[E280Tim]

Thanks guys I'll try to get it booked in.

I do have a code reader that does live data can anyone tell me which readings I should check?

 

[LvR]

From before:

monitor real time data on the pre cat O2 waveform - also pay particular attention to the values of short term and long term fuel trims - if the ECU is in proper control of the engine you should see short term values fluctuating around 0 by a few % (average should be close to 0) and long term should be a constant value typically under 10% if the engine is in good condition.

Report those ST and LT values here as well as a typical O2 graph you see (somebody can comment) - if they are behaving normally then high fuel consumption is not caused by the ECU

 

[E280Tim]

Please bare with me here as I'm new to live data etc...

I'm not sure how to read ST/LT fuel values or if my little reader is even capable of doing this but below are some of the reading i've taken with the engine warmed up and at tick over.

DTC-CNT 0
Load PCT 22
ETC 88
MAP 100
IAT 38
MAF 13.86
FRP 27690.0
EQ RAT B1S1 1.999
O2 B1S1 1.5

As I say most of this means very little to me so I'd be very grateful if anyone could help decipher these.

Thanks

Tim