1998 S320 94kmi. Noticed delayed then hard shift when accelerating, usually above 3,000 rpm. NO codes. Saw that some people claim its the MAF, but I checked it accordingly to what my scanner told me to do:

KOEO (spec: .98-1.03v)... was 1.02v OK
Idle (spec: 1.32-1.48v)...was 1.36v OK
@2500 (spec: 2-2.2v)... was 2.16v OK

And the thermistor seemed to be doing its job changing resistance as temp went up. I payed attention to the output on the graph on my scanner and i saw no kind of glitches. So I think the MAF is OK?

I do however have that leak on the transmission connector "conductor plate" that everyone says could be causing the modulator to be bad. Before i try and replace this, can anyone tell me how I can make sure this is causing my problem?

Any engine codes OR transmission codes??

Of course there aren't any real MAF specs because they are subject to conditions!
temp, altitude, humidity...ect

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MERCEDES Benz Master Guild Technician (6 TIMES)
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Retired Moderator

Don't mean to butt in, but we are having the same problem.

It is a 97 S320 and it has gotten progressively worse, to where it is in limp mode. So, with some help from everyone, maybe we can fix two members cars.

TIA

As pointed out, what codes are in the engine & trans???

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

I got the specs from my snap on scanner for the voltage outputs? What else can I do to test it? Absolutely NO CURRENT CODES OR HISTORY-or at least my scanner is not giving me any, even after I floor it.... The trans will really do some erotic things, especially when I floor it. If I floor it all the way to trip button under the pedal, the almost feels like it slows down! I know there is alot of misfiring going on because some times I can hear backfire from the exhaust. It also misses very bad when the motor is cold, I can barely get it to 2K rpm! This is the same problem Ive read others have and they all say its the MAF? Should I try to replace the MAY anyway? An ebay cheepee or buy a Bosch?

THANKS FOR YOUR RESPONSE!

Start with the obvious. Low power suggests a fuel system related issue.

The MAF is responsible for 90% of fuel system input.

USE only a Bosch complete air mass sensor!

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

I just checked the fuel pressure and it was right where it should be even after I unplugged the vacuum on the regulator. I just ordered new MAF.

I CAN'T BELIEVE IT! IT WAS THE MAF!!! What I thought was a trans issues because of a hard shift was an engine misfire issue all along. I guess I thought it was the trans because it shift hard over 3K RPM. But the motor starts its power band around there. So actually what was going on was since it was misfiring over 3K RPM and had less power, (I bought the car with this problem) I couldn't' notice it was missing because I thought the power band was flat and the trans was just shifting hard. But the trans was doing its job at that RPM. THIS THINGS RUNS SO MUCH BETTER!!! EVEN AT IDLE!!!

THANKS DOC!!!