I have an 03 E500 with 55,000 miles and everytime it shifts at low throttle it does a "Hesitation" almost like a misfire or shake a couple of times. First opinion by the dealer was the transmissionhad a problem. Second opinion by independent said trans was fine that it was a sensor in the catalytic convertor. Took back to dealer they said all the motor mounts needed to be replaced. Took to another dealer and they now say it needs new plugs and wires and that the motor mounts are fine. Before I shoot a mercedes mechanic has anyone else had this problem and knows whats going on. If I did everything it would cost me over10 grand!!

 

Hi Aaron,

Good idea going to several garages!
I never cease to be amazed by the diversity fof opinion!

Difficult to state what might be the cause BUT would first see whether the car knows what is wrong with itself.
Get the OBD codes read. Small charge but this might just point the finger at something. Codes can be stored without the Check Engine Light on.

Is your Service History up to date? Filters, plugs (55k is just past or just before the service change point dependent on market) and also get the trans fluid level checked while you are at thedealer having the codes read just in case (unlikely)

03 / 55k is not particularly old so would not think it would be the engine mounts...but not impossible.

The trans is linked to the engine electronically and various controls ensure engine emmission sare controlled during warm up (and once warm). Things like gear change point, gear selected etc. so it is conceivable that the cold emmission controls are the cause BUT you suggest it is with engine cold and warm.

Is problem JUST when driving away COLD SLOWLY or does the same problem occur when engine is WARM or driving away more BRISKLY?

It is quite possible it is the MAF getting near to the end of its life but lets start at low cost first.

Stuart.

 

Thanks for the info....
To follow up, The hesitation happans always, hot cold warm fast slow etc. it is more pronouncedI feel once the car warms upa and at lower RPM. It is time for new plugs so i don't mind having that done. From underneath all the mounts look perfectly fine except for one that has some minor cracking in the rubber, but no more that any of my other vehicles.The suggestion for the catalytic convertor came from them reading the codes, nothing else popped up. The dealer reset everything to see if the code comes up again and it's been a month and nothing. Never thought about the MAF. I love the car I am just so frustrated I've considered dumping it and buying something else.

 

Considered dumping it. A bit drastic! So far I've invested about 2 mins on this problem!

Cracks in the engine mounts? The important bit on the mounts is the rubber / metal bond rather than the rubber itself. Since the mounts are designed such that the weight of the engine keeps this junction in compression it is difficult to see if the bond is OK unless the car is jacked under the engine using the engine jacking point...or similar. Anyway I don't believe this is your probl;em.

OK. So you DID have codes and somebody put this down to the cat. What were the codes? This is a lead worth trying to follow up although I believe the cats will be OK unless they rattle when cold!! in which case there is a mechanical problem with the construction of the cat rather than the cat not working.
Codes don't state...RH cat defective. They tend to state. Misfire Cyl 1, Fuel trim out of range etc so the code has to be translated into a component problem. This requires knowledge/ experience.
In turn Fuel Trim out of range can be caused by a number of issues from incorrect fuel pressure, faulty injector(s), faulty MAF, faulty O2 sensor, air temp sensor, knock sensor etc etc etc.
You say you have No codes at present since the system was reset. Do you actually mean NO CODES or have you assumedthat there are no codes since the CEL Check Engine light is NOT on?

After ensuring your service history is up to scratch I'd go for MAF. The best way to confim this is to look at the LTFT and STFT readings. These need to be read with an OBD scanner that has live data feed capability...so maybe its back to the garage for the scan. Please advise LTFT (Long Term Fuel Trim) readings. This will clearly show if its the MAF.

Have you checked out the engine harness / plug leads although once again these are not particularly high on my hit list.

Oh. Just thought. What fuel are you using. Regular or Premium?

Stuart.

 

Oh, .....and just incase you race away and buy a MAF ensure its a GENUINE Mercedes spare that you purchase. Others manufacturers product work but can introduce problems similar to that you are experiencing because their characteristics are not correctly matched to the application.

 

They never told me what the codes were. I'll get it checked again and let them know your suggestions. The car has only had premium put in it usually from Shell or Chevron. The check engine light has never come on even when the problem started.

I'll go thru all the plug leads and harness today. I purchased new bosch plugs and was going to install them.

 

Aaron, did you come to a resolution with your E500 hesitation? I also have an 03 E500 that is doing the exact same thing. Mine has 94K miles on it. I have no gycol in the tran fluid - no one seems to have an answer.

Any information is much appreciated.

 

Hello,
Has anyone figured this problem out... I just bought 2003 e500 with 70 k miles on it and its really acting funny when shifting...its like misfire , no engine light on ....

 

you likely have a defective radiator - the Valeo brand - if you have one replace it with a Behr brand immediately and have the transmission flushed until the hesitation stops.

the defective radiator allows coolant to leak into the torque converter - which in turn, allows coolant into the transmission - hence the reason for your hesitation.

if you don't act quickly your transmission will go out and you may need a new torque converter as well.