jquash3

I have recently had a problem with my 2000 ML430 with 33K miles on it. The dealer diagnostic is unable to identify and resolve the issue, so I am looking for help. The problem typically manifests itself after I have been driving for a couple of hours... at around 70-80mph the car will hesitate and speed will reduce to about 65mph and then operate normally again. This happens with and without using the Cruise Control (so that's not the issue). If I put my foot on the gas more, the RPMs build but speed continues to reduce to 65mph before it operates normally again. When the power lose occurs the car chugs. I do have some suspicions about the cause but would like to find a person of knowledge that can help me make this problem go away. I can't believe the diagnostic can't find a fault.

mihir_d

So that is nothing surprising...

1. My CATs leaked to the point of the car almost sounding like a steam engine...yet, diagnostics didn't think anything was wrong.

2. My MAF needed replacement...still diagnostics doesn't see anything wrong with it.

The effects of the bad CAT and bad MAF were far too obvious on the truck...the exhaust noise and the significant drop in mileage..both got resovled ones the CATs and the MAF were replaced, but no fault codes nothing on the truck ever appeared...

jquash3

Mihir, thanks for the reply. As I am acronym challenged could you please define CAT and MAF (I thinking it's catalytic converter and Mass Air Flow sensor... but that's just a best guess). Also do you have any guess/estimate as to what I will have to spend to get it fixed.
Thanks, Jim
P.S. My wife's name is Subhashini

mihir_d

I think, yours is probably a tranny problem, which the On Board Diagnostics OBD is unable to register a fault code for...

It could also have something to do with either air or fuel intake, but that can be verified by reving the engine up at stand-still and see if you see any abnormaility in a certain RPM range.

If not, your problem is most likely with the tranny. Hard to guess, what it would cost to fix it, since tranny are difficult to fix, especially for a truck like this.

I have one estimate though...if it comes to replacing the tranny, you are looking at a cool $5K.

Good to know that you have a wife of (East) Indian origin.

jquash3

My initial thoughts were air/fuel mixture issues. Either a sensor or injector thing. My MB service guy mentioned fuel pump, but I think it would occur more frequently. Hopefully it's not the tranny!!

Thanks for the insight. Jim

P.S. Actually Sri Lankan

Kar don

i would think its a MAF sensor.

mrkbbd

its the fuel pump, I had the same problem