MPG Dropping... and Dropping and... DROPPING

[iamcpap]

Hi everyone. I'm sure there are other threads about this, but I wanted to explain my car's symptoms exactly.

I have a 2010 X5M with 69,XXX miles on it, it has always been under warranty from Factory to CPO to Bumper to Bumper Warranty covered all the way thru 2020. Good news...

When I got the car last July, I was averaging around 12-14 MPG overall, over winter I noticed it dropping to around 10-11MPG and most recently, I am averaging 9MPG or even less... Same kind of driving, no different routes or trips, etc...

Car runs fine, no weird idle, no CEL, although some days it smells like the car is running rich, the exhaust smells sweet, etc. But not every day.

Plugs were replaced under warranty at 53k miles on cylinders 5,6 & 8 and the injectors were all replaced on bank 2, according to the service history paperwork.

What I don't want to do is just start throwing money at everything until I find the problem.

Some things people have told me:
1. Walnut Blast? Carbon buildup cleaning?
2. Replace air filters with K&N? Not sure when they were replaced last.
3. Injectors
4. Spark plugs

Anyone have any suggestions? Feel free to chime in...
Thanks in advance,
Chris

[m5james]

1) Walnut blasting is much harder to access on the reversed design of our V8 vs an I6. I've heard you might even need to lift the engine. I've seen pics though, and it seems gravity helps keep oil residue off the valves
2) You could just because they'll help a bit for better airflow. The S63 doesn't have a MAF, so don't worry about over oiling issues others mention with using K&N.
3) Them replacing only one bank is just being lazy and cheap. I'm going to assume it's injectors. Is the back of the truck peppered with little black dots are a HARD drive? If so, that's unburnt fuel due to leaking injectors. Best case scenario is bad mileage, worst case scenario is the engine hydrolocks when they leak over night. A cold start one morning and mine finally gave up...ran super lumpy, plumming smoke, I shut off right away.
4) Depending on how you drive, mods, etc they'll last about 50-100k.

[JDAURIA]

delete*

[JoeyBimX5din]

If your under warranty why are you asking here? You should be at the dealer telling them all this

[m5james]

Originally Posted by JDNY516

I think I read somewhere the injectors need to be replaced around 50k and they aren't cheap. You mention spark plugs? What maintenance intervals have you been using? I usually change mine out on the M5 every 25k miles. Air filters won't yield a big difference personally. Your vehicle doesn't have to throw codes for something to be wrong. When my M5 was down on performance it ended up being the Camshaft Position Sensors (CPS) were done. Replaced all 4 and it was night & day difference. No codes at all

Replacing injectors every 50k would be absurd, even if you'd bought them on the cheap at Rockauto for $100 each. What I think you're referring to is people replacing the ignition coils on those kinds of intervals, some even less, but they're also the guys who are pushing 700+hp and they're doing it for precaution. Interesting about the CPS though, I'll have to look into that. How many miles do you have on your M5?

[m5james]

Originally Posted by JoeyBimX5din

If your under warranty why are you asking here? You should be at the dealer telling them all this

The dealership already cheaped out by only replacing one bank, not to mention most times they won't do anything until a CEL is kicked.

My injectors were leaking for I'm guessing a month or so because I kept getting the peppering I mentioned above. Their final demise was going 170mph late one night when they finally failed. Thankfully I had an OBDII reader in my car and was able to reset the codes once it went into limp mode, still drove it home with no issues. The next morning was a completely different story as no amount of code clearing would allow it to run right and that's when I knew they were done. Long story short but I had to pay outta pocket for my injectors but eventually was reimbursed. I was getting a reduced power warning for almost 6 months, no CEL was kicked, but sometimes I'd get a pending code for boost pressure sensors which ended up all getting resolved from a vacuum leak.

Point being is their sometimes dummy mechanics and SA's won't touch it unless a dummy light is on, which even then doesn't tell the whole story. I wish I had a CPO though :-)

[JoeyBimX5din]

The thing about the limp home mode is, that it is setting a code. Though it will not always set a check engine light, there is a code there when you hook up with Reingold. At least that is the experience I have had with my current limp home issue, coming from boost sensor 2 I believe, could function differently for folks elsewhere, but I doubt if you hook up with an actually BMW OEM scan tool, it will not see something in the historic.

Still, why waste your own time when your under warranty. Warranties need to be utilized the way they were intended. I deal with dealer vendors all the time, once you put a bit or pressure, they usually cave and do what they are supposed to do. Although I do have the weight of a few hundred pieces of equipment behind me, the same applies to just one person. Worst case scenario, call up BMW NA, get them involved. Something is most obviously wrong with this truck, and needs to be addressed with a dealer warranty repair.

[iamcpap]

Originally Posted by m5james

1) Walnut blasting is much harder to access on the reversed design of our V8 vs an I6. I've heard you might even need to lift the engine. I've seen pics though, and it seems gravity helps keep oil residue off the valves
2) You could just because they'll help a bit for better airflow. The S63 doesn't have a MAF, so don't worry about over oiling issues others mention with using K&N.
3) Them replacing only one bank is just being lazy and cheap. I'm going to assume it's injectors. Is the back of the truck peppered with little black dots are a HARD drive? If so, that's unburnt fuel due to leaking injectors. Best case scenario is bad mileage, worst case scenario is the engine hydrolocks when they leak over night. A cold start one morning and mine finally gave up...ran super lumpy, plumming smoke, I shut off right away.
4) Depending on how you drive, mods, etc they'll last about 50-100k.

Thanks for the insight...

Originally Posted by JoeyBimX5din

If your under warranty why are you asking here? You should be at the dealer telling them all this

Originally Posted by JoeyBimX5din

The thing about the limp home mode is, that it is setting a code. Though it will not always set a check engine light, there is a code there when you hook up with Reingold. At least that is the experience I have had with my current limp home issue, coming from boost sensor 2 I believe, could function differently for folks elsewhere, but I doubt if you hook up with an actually BMW OEM scan tool, it will not see something in the historic.

Still, why waste your own time when your under warranty. Warranties need to be utilized the way they were intended. I deal with dealer vendors all the time, once you put a bit or pressure, they usually cave and do what they are supposed to do. Although I do have the weight of a few hundred pieces of equipment behind me, the same applies to just one person. Worst case scenario, call up BMW NA, get them involved. Something is most obviously wrong with this truck, and needs to be addressed with a dealer warranty repair.

It's an aftermarket warranty... dealer (and warranty company) can and will only do so much when there aren't codes being thrown, which there aren't... also, if it is just wear and tear, it isn't covered under warranty.

I know how to use a warranty, BMW NA won't do anything on a 2010 with nearly 70k miles that has an aftermarket warranty... but I appreciate the thought...

[JoeyBimX5din]

Oh, I am sorry to hear that. Aftermarket warranties are mostly, so bad, they are not worth using the paper they are printed on to clean your rectum after defecating.

Are these high pressure fuel injectors in the engine oil at all? Could there be a fuel leak somewhere?