C220cdi Still poor mpg

[streaker]

Hi

I posted recently concerning my sudden onset of poor MPG

I have now had the car on STAR at a recommended indy and the only fault found were 2 injectors out of spec, these have been replaced and a slight miss fire and pinking noise have gone, but she still puts out plenty of black smoke on heavy acceleration and will only do 32mpg the MAF is new and the values are good as well as the EGR.

when the MAF is disconnected I can easily get mid 40's - 50mpg with good power and very little smoke,

The reduction in MPG happened at sometime during a 3 day period when I was commuting only 4miles to work, I only noticed it on my normal friday night 200 mile trip home

So must be over fuelling with maf plugged in, but what could cause this without showing a fault on the Star ?

Please help

Jaz

 

[paul hayward]

try a V8:lol:....thats interesting on the MPG:lol:

sorry cant help but good luck sorting

 

[andy@pcd-ltd]

What temp does the engine run at

 

[bigtwin]

Have you cleaned the thing? I had a prob that wasn't quite as severe as yours, but a freshen up rendered an extra 5+ mpg. Nothing form the STAR, didn't realise that it was batting below average till I trawled this site for performance figures*.





* Massive sycophantic plug - do I win a free T-shirt?

 

[streaker]

Engine gets up to 90c within 4 miles from cold (recent new thermostat and coolant)

Runs great without the MAF but is more refined and a bit more power with it plugged in just the annoying smoke and much lower mpg

Bigtwin cleaned what ?

Cheers Jaz

 

[jj1975]

Hi
If it its smoke when you accelerate there must be air leak somewhere check the hoses from turbo to the EGR valve and the intercooler for any split or EGR valve sticking open

 

[bigtwin]

Engine gets up to 90c within 4 miles from cold (recent new thermostat and coolant)

Runs great without the MAF but is more refined and a bit more power with it plugged in just the annoying smoke and much lower mpg

Bigtwin cleaned what ?

Cheers Jaz

The MAF. Isoprop the insides etc.

 

[streaker]

Hi Bigtwin

the maf's Brand new less than 400 miles and is right on spec according to the Star readings
but thanks for repling

Cheers

 

[streaker]

Hi jj1975

my indie is going to check the egr next although its fairly new and the Star reports its readings are in parameters, I cant hear any out of the ordinary turbo noise or air sound's and there seems to plenty of boost, the acceleration is very strong, could a small inaudible air leak cause 20% reduction in mpg ?
Thanks
Jaz

 

[Steve@Avantgarde]

Have you had this chipped/remapped?

 

[streaker]

Hi Steve@Avantgarde

I was told by the garage i bought it from that it was remapped (to have the dpf deleted) I believe the power has been upped as well,
I ran the car for a month, 500 miles per week mostly motorway and was getting around 46 - 50 mpg on the motorway and around 35mpg in town on very short journeys, then suddenly it dropped to 28 - 31mpg motorway and town
I picked it up today after 2 injectors were replaced, the mpg is still the same but there is a lot less smoke, after 40 miles I unplugged the Maf and instantly got 48mpg at 70 on the motorway
I would happily bring the car into you as I only live 30 miles from you but unfortunately I'm working in Liverpool until end of Jan

Cheers
Jaz

 

[IceBoy]

Sounds like an air leak.

I had this same problem a few years ago. Problem is that air leaks can be a pain to find.

IceBoy

 

[streaker]

Thanks IceBoy

its in having a new heater matrix next week ( couldn't shift the restriction - Damm !!!! )

I'll get them to look for an air leak

cheers
Jaz

 

[Steve@Avantgarde]

2 things that spring to mind on this.

The DPF pressure sensors have been modified. Even though the DPF is deleted the engine management still needs a value from this sensor so technically, its not deleted from the system. I have had a few of the 646 engines suffer poor economy because of this sensor. Now whether this would have an effect on your car I dont know, the values would have to be checked.

The other thought I have is that of a fractured intercooler. I have a C220cdi that started black smoking a bit and it lost a bit of economy too. I had a tiny split in the intercooler, not enough for it to drop power but enough for it to play up in other ways. This could explain when you disconnect the MAF it runs better. The MAF is measuring unmetered air, when its disconnected, it runs a basic setting. On the flip side to that, its not a hot film system and disconnecting MAFs on diesels doesnt normally do a great deal.

This is a confusing one for sure but I am willing to bet the remap and DPF delete has something to do with it somewhere if its not a leaking intercooler.

 

[streaker]

Hi steve

It certainly seems like a component /sensor problem or an air leak
as the economy dropped instantly, I just didn't notice it until I went on the motorway, the smoke has reduced a lot since the injectors were changed although it reduces to normal levels with the Maf unplugged,

Can I just confirm that leaving the MAF unplugged for an extended time will not harm it or anything else ?

Many Thanks Jaz

Ps if i have not resolved this problem I would like to bring the car down to you in early feb to give it the once over

 

[Steve@Avantgarde]

I cant imagine it doing any harm leaving the MAF disconnected. Just keep an eye on it.

 

[streaker]

Thanks steve

I presume your comment re the MAF not having a hot film means it wont cause any problems with the MAF when I eventually re connect it ?

Jaz