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Auto Psychic
Auto Psychic, Mercedes Technician
Category: Mercedes
Satisfied Customers: 1437
Experience:  semiretired mercedes benz master guild technician w 4+ decades of diagnosis and repair experience
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Mercedes-Benz ml 320: 2000 ml320 ,150k-no acceleration trouble,engine

Resolved Question:

2000 ml320 ,150k-no acceleration trouble,engine idles fine.(code thrown) I changed the Tps/pedal value sensor, no accel(the throttle valve has no power). So after that expense I started tinkering(for hours), I can only get the car to accel by disconnecting the maf harness,turn key to on (position before start),And disconnect /reconnect battery, (i can hear the throttle valve whining continuosly) then turn key to start, the car will start idle and accel ,i can reconnect maf while idling and still have accel.Until the car is turned off .If engine is restarted within 2-3 seconds still accels, if 5 seconds or more pass to restart then no acceleration again (throttle valve can be heard whining for 1-2 seconds then dies while trying to start if i left the maf connected). So what do you think this could be I thought it might be throttle valve but it will throttle if done in the above order every time . i did first part of the test with the throttle valve exposed(plastic off) so i could tell when the valve had power. movement (cant be moved by hand when energized),suction(with my hand on/in throttle valve) ,sound (high pitched whine from valve motor housing) .
Any help would be great.
Submitted: 2 years ago.
Category: Mercedes
Expert:  Auto Psychic replied 2 years ago.

Auto Psychic :

hi, i'll be happy to help you in anyway i can.

Auto Psychic :

sorry to hear of your misfortune :(

Auto Psychic :

fairly creative set of diagnostic steps you've devised, not sure i even follow them lol

Auto Psychic :

anyway, you almost certainly have a bad throttle actuator, its really the only thing that could cause your symptoms.

Auto Psychic :

check out beckmanntechnologies and programainc.com for a rebuilt.

Auto Psychic :

the bad news is you will need someone with a dedicated mercedes laptop to 'marry'' it to your vehicle.

Auto Psychic :

let me know if you need anything else.

Auto Psychic :

good luck, gary

Customer:

is the high pitched whining hum from the throttle actuator normal when its recieving power(key on)? and when you say 'marry' ,while i get the concept , will the new throttle work without the marrying process ,at least enough to drive to the dealer for the marry process.? in other words is the marrying process to function period, or, to function efficiently ?

Auto Psychic :

the whining may or may not be a problem, they make a bit of noise so without hearing it, its a bit hard to say, but the loader it is the more likely its bad.

Auto Psychic :

the marrying process is necessary for it to function at all.

Auto Psychic :

if the engine control module doesnt know where the throttle stops are it wont work at all, sorry.

Auto Psychic :

your best bet is find an independent mercedes specialist who'll work with you.

Auto Psychic :

dealerships tend to shy away from afterrmarket rebuilt parts.

Auto Psychic :

does that help?

Customer:

I found a great example that fit my situation to a tee here--> http://www.justanswer.com/mercedes/5dh2v-mercedes-benz-ml320-ml320-will-not-rev-1100-rpm.html

Customer:

it would seem the computer is seeing a fault in the Throttle Valve and shutting it down ,that would explain the p0120 code even after a new TPS/PVS was installed . Disconnecting the battery obviously suspends/erases the halt to the Throttle Valve. What I dont get is ,why starting the engine with the MAF sensor disconnected allows the Throttle Valve to function and accelerate with pedal push,while starting the engine with the MAF connected will only allow the engine to fast idle(1100rpm).

Customer:

Thanks for your help , I'll try the Throttle Valve Actuator

Auto Psychic :

me either lol,

Auto Psychic :

i cant get to the link, what did it say??

Customer:

http://ww2.justanswer.com/uploads/eurotec/2011-08-06_174030_p0120.pdf

Customer:

p0120 --- mbme28desc-022b

Auto Psychic :

wow, dont know how you ever found that link :)

Customer:

been at this non stop for over a week

Auto Psychic :

dont tell anyone but marty (eurotec) is as good as it gets.

Auto Psychic :

cheerio

Customer:

All of this battery on/off business has caused my radio to want for a security code (my vin is 4JGAB54E51A258698 ) 2001 ml320 can you help with this or do i need a dealer for this too?

Auto Psychic :

your code is 21521

Customer: Thanx a bunch, code worked! I'll let you know how i make out
Auto Psychic, Mercedes Technician
Category: Mercedes
Satisfied Customers: 1437
Experience: semiretired mercedes benz master guild technician w 4+ decades of diagnosis and repair experience
Auto Psychic and 3 other Mercedes Specialists are ready to help you

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