92 300D loses acceleration above 2200RPM - PeachParts Mercedes-Benz Forum

jia300d · #1 05-01-2014, 08:39 AM

Hey there, my 92 300D is experiencing lose of power when I accelerate hard and the engine gets to the 2200 RPM mark. It seems to me that the turbo does not engage and I am trying to find out some good Troubleshooting instructions. I can get decent acceleration and shifting up to 2200 RPMs. If I press the accelerator hard it accelerate normally and at the 2200 RPM point it slumps. If I continue to accelerate very very gradually it will get up to speed and go over the 2200 RPMs but again very very gradually. Thanks for any help you can provide.

vstech · #2 05-01-2014, 10:16 AM

I moved your post to it's own thread to get better responses!

jia300d · #3 05-01-2014, 10:38 AM

Thanks!!

DieselJim · #4 05-02-2014, 09:24 AM

Turbo doesn't kick in until about 2400/2500. Its likely a fuel issue. Also turbo failure won't stop the car from accelerating it will just lower the torque and horsepower boost when it kicks on and might mess up the shift points

First thing to check is your fuel filters. If you see a lot of diesel algae in the primary/inline filter then plan on changing the in tank strainer in addition to the inline and spin on. The filters may very well need change.

I never had any issue with the turbo but always check your vacuum tubes to the alda and waste gate to make sure the turbo is activating once you do hit minimum RPMs for it to spool up

And of course air filters. Good luck

vstech · #5 05-02-2014, 10:15 AM

on the 92, I gotta disagree...

my 87 190 2.5Turbo the boost is instantly available, and I can feel it build as I accelerate. his drop off in power at the 2200 mark is likely a fueling issue, but the boost should pull strongly in that motor from 1000RPM or so on up.

OP:

you'd need a boost gauge to verify if boost is "dropping off" but keep in mind, FUEL is needed to get power from the boost. if your primary, or secondary fuel filters are partially plugged, they could limit fuel flow above a certain RPM, and cause the power drop your are feeling.

it could also easily be the plastic linkage ends MB put on those motors... inspect your throttle assembly for damaged plastic parts.

jia300d · #6 05-02-2014, 12:30 PM

I will inspect/change the fuel filters and strainer this weekend. I checked yesterday the ALDA vac line and fitting and they are clear. To check one more thing, does anybody have troubleshooting instructions for the switch-over valve?
Since the power loss took place from one day to another It could be a fuel line or filter that clogged (no algae though). Thanks.

jia300d · #7 05-02-2014, 12:40 PM

Never mind, I just found instructions to test the Y3/3. Since it controls the upshift and the car is upshifting all the gears by the time it gets to the 2200 RPMs (40-50 mph) I have the gut feeling that it might have something to do with the problem.

DieselJim · #8 05-02-2014, 09:36 PM

Quote:

Originally Posted by vstech

on the 92, I gotta disagree...

my 87 190 2.5Turbo the boost is instantly available, and I can feel it build as I accelerate. his drop off in power at the 2200 mark is likely a fueling issue, but the boost should pull strongly in that motor from 1000RPM or so on up.

OP:

you'd need a boost gauge to verify if boost is "dropping off" but keep in mind, FUEL is needed to get power from the boost. if your primary, or secondary fuel filters are partially plugged, they could limit fuel flow above a certain RPM, and cause the power drop your are feeling.

it could also easily be the plastic linkage ends MB put on those motors... inspect your throttle assembly for damaged plastic parts.

I put a 170K freeway miles on a 92 300D. The Turbo didn't spool up that strong until 2500. It is a surprisingly strong engine

DieselJim · #9 05-02-2014, 10:57 PM

Max boost is about 2700. Yes the turbo does help at lower RPMs but I personally always noticed that kick around 2400/2500 it gets to the sweet spot. Had to master it to survive Atlanta traffic. I have done fuel filter changes on the side of the interstate or at truck stops on trips. Always keep them handy

jia300d · #10 05-15-2014, 02:43 PM

Hey guys, I have been horribly busy and was not able to clean the strainer yet but today I noticed something in particular when I was entering the interstate at a painfully slow rate of acceleration that is making me scratch my head. I was slowly accelerating past 60 mph with RPMs around 2000, I floored it to see what it did and guess what, a big black puff of unburned diesel through the exhaust without any resulting acceleration. Could it be that the mix is too rich rather than starving?