2005 E320 CDI seems underpowered - PeachParts Mercedes-Benz Forum

65aircooled · #1 05-02-2014, 06:33 PM

Quote:

Originally Posted by jcyuhn

If the injector spray pattern/atomization is messed up, I can see the results being low power and poor fuel economy due to poor combustion - it kinda makes sense. But then I would also expect there to be an observable difference in the way the engine runs - either idle noise, or perhaps additional black smoke under acceleration.

Unfortunately the piezo injectors are very expensive (~$500 each), so swapping them on speculation isn't feasible. I wonder if there are services which can test/evaluate/recondition them?

No Piezo injectors in the CDI, still won't be cheap tho

Josh8loop · #2 05-21-2014, 08:48 PM

I am having a similar issue. When I first bought the car I was getting 32MPG in town. Over the last year or so the fuel economy has been slipping to the point now where I'm at around 26MPG for the same type driving. No codes in the computer according to ScanGage. Power has always been lower than it should be as indicated by the 9 plus second 0-60 time.

I keep track of the fuel economy on Fuelly.com so that helps in comparisons. Air, fuel filters, Glowplugs, thermostat(with temp sensor) have been changed. I cleaned the EGR valve, the MAF sensor, MAP sensor, and dielectrically greased most all electrical connectors under the hood in an attempt to maintain the vehicle and also to regain lost power & fuel economy. I even removed and reseated the fuses in the fuse box to ensure I didn't have any high resistance contacts there.

After reviewing the information online about how this injection control scheme works and the various sensor inputs I am wondering if I have a fuel temp sensor problem or perhaps an O2 sensor issue. Both those inputs help the vehicle decide how much fuel to use by way of adjusting fuel rail pressure and fuel injection duration. I am currently testing my fuel temp sensor which according to CDI literature should be a NTC(negative temp coefficient) type. Not sure what the resistance per temp spec on it is however.

I wonder if the OP has considered checking or replacing the fuel temp sensor or perhaps the O2(Lambda) sensor?

65aircooled · #3 05-21-2014, 09:04 PM

That's interesting. I have not had the car for long, in fact I have put less than 3K miles on it. My in town mpg's have always been around 26.5 to 28 and no more than 35 for highway, though I like to keep the go pedal on check to keep the EGR clean

I always thought the power was very good, but now I am starting to wonder if my car is suffering from the same and I just don't know better

I have no hard or soft codes either and the car runs as smooth as butter. I have read at least one member's comments about his car feeling like a "rocketship" and a "wild horse" that could easily slip out of control.
The only two cars I ever drove that gave me that particular feeling was a V10 Dodge Viper and a Porsche 911 turbo, and my CDI, although a very peppy car, doesn't even come close to that.
I hope my low mpg's are more related to my right foot rather than a motor related issue.
I'll be getting the bag of popcorn for this one...

spark3542 · #4 06-06-2014, 02:39 PM

Just a data point.... I purchased my 05 in 2010 with 130k on the clock. It now has 229k and 99% of those 99k miles were on homemade BD.

Mine still accelerates like a bat out of he** just like it did the day I got it. I won't even let my 16yr old son drive it because of the acceleration.

I recently had some shifting issues, so I sprung for the aftermarket tranny dipstick and did fluid and filter change. Back to normal health now.

During some of my shifting issues, it was evident that the tranny seems to have the ability to restrain the engine. You may want to look at the tranny as a contributor to your problem.

On BD, I will get 32mpg all day long. The very rare occasions of pump diesel, it will get 37.

courtney · #5 03-30-2015, 05:15 AM

josh my mpg drops off a lot if i have any injector seals leaking, and i had some leaking that evidently did not leak long enough or bad enough to build up carbon around them

could not tell my looking at them

but put some gas leak tester on them and found 2 leaking

changed those and mpg back up by 4-5mpg

my plan is to change out the injector seals every 75,000 miles now or earlier if i get any leaks , and i will do them all at once instead of one or two at a time

DieselDummy · #6 04-01-2015, 09:02 PM

Quote:

Originally Posted by courtney

josh my mpg drops off a lot if i have any injector seals leaking, and i had some leaking that evidently did not leak long enough or bad enough to build up carbon around them

could not tell my looking at them

but put some gas leak tester on them and found 2 leaking

changed those and mpg back up by 4-5mpg

my plan is to change out the injector seals every 75,000 miles now or earlier if i get any leaks , and i will do them all at once instead of one or two at a time

Thanks for the info. Can you expand more on your method of testing?
Thanks

Skid Row Joe · #7 06-05-2015, 04:59 PM

Quote:

Originally Posted by DieselDummy

Thanks for the info. Can you expand more on your method of testing?
Thanks

X 2.....especially the mpg "testing"....? I asked too.....

Josh8loop · #8 06-05-2015, 03:59 PM

Quote:

Originally Posted by courtney

josh my mpg drops off a lot if i have any injector seals leaking, and i had some leaking that evidently did not leak long enough or bad enough to build up carbon around them

could not tell my looking at them

but put some gas leak tester on them and found 2 leaking

changed those and mpg back up by 4-5mpg

my plan is to change out the injector seals every 75,000 miles now or earlier if i get any leaks , and i will do them all at once instead of one or two at a time

Great information there! Funny because I just looked under the hood a few days ago to see very early start of "Black Death" on cylinder #1 injector. I used BrakeKleen, and STP carb/choke cleaner and it all cleaned up really nicely. I'm waiting for the tools now to get that injector out and new seal and new bolt installed. It looks like it happened in the last 500 miles since my fuel economy went from 26 to 21 MPG over that time. My question to you is you mention gas leak tester....Would soapy water work just as well? Maybe Snoop?

Skid Row Joe · #9 06-05-2015, 04:57 PM

Quote:

Originally Posted by courtney

josh my mpg drops off a lot if i have any injector seals leaking, and i had some leaking that evidently did not leak long enough or bad enough to build up carbon around them

could not tell my looking at them

but put some gas leak tester on them and found 2 leaking

changed those and mpg back up by 4-5mpg

my plan is to change out the injector seals every 75,000 miles now or earlier if i get any leaks , and i will do them all at once instead of one or two at a time

I don't think it's possible to reduce mileage by "4-5mpg" from "2 injectors" that would require a "gas leak tester" to detect those leaks.

IIRC, weren't you the guy that claimed his '99 E300 was getting in the "45mpg range," last year?