2001 ML430 Misfire codes

[Pikes]

I recently bought a used 2001 ML430.
140000km`s on the clock
Lovely car in very good clean condition and drives like a dream when going below 120km/h.
The problems start when I drive a bit harder on the accelerator pedal.
After driving at high speeds and you slow down for a stop street or traffic light the car have very rough idling. When you then drive off you can feel that the car is not firing on all cylinders.
Switch the car off and then on again, smooth as silk again --- until I do a hard acceleration again.
There is never any warning lights on the dashboard when this happens.

I took the car to MB for a diagnostic test and they told me it would cost +/- US$4500 to fix.
I dont have any spare money at the moment to throw at this problem and would like to fix the broken part/s on the first round. In other words i dont want to replace any unnecessary parts that did not need to be replaced.
You know the feeling I`am talking about.

These are the problems that the control unit spit out:

Code Text
P2050 Misfiring, damages TWC (see currently valid STIP) (P0300)
P2043 Misfiring (see currently valid STIP) (P0300)
P2045 Misfiring of cylinder 5 (see currently valid STIP) (P0305)
P204A Misfiring of cylinder 7 (see currently valid STIP) (P0307)
P2052 Misfiring of cylinder 5 Damages TWC (see currently valid STIP) (P0305)
P2057 Misfiring of cylinder 7 Damages TWC (see currently valid STIP) (P0307)
P2053 Misfiring of cylinder 4 Damages TWC (see currently valid STIP) (P0304)
P2056 Misfiring of cylinder 3 Damages TWC (see currently valid STIP) (P0303)
P2082-004 G3/3 Left O2 sensor before TWC{KAT} Open circuit (P0154)
P200F-004 G3/4 Right O2 sensor before TWC{KAT} Open circuit (P0134)

Any suggestions as to this problem would be appreciated.
Thanx in advance

[Loudgoldwing]

Noticed that you were told that it would cost $4500 to fix, but were you not told WHAT needed to be fixed that would cost $4500?

For a better answer to your question, please review the report your dealer gave you, and tell us what they wanted to replace that would cost $4500. We can then probably give you some good suggestions on what to do.

Fear not, good sir... We're here for you, and we're willing to help. We just need the proper information to do so.

Cheers

[FAR888]

I agree with Loudgoldwing.

I think that the experts would require information like Long Term Fuel Trim and Short Term Fuel Trim.

Do you have a OBDII scanner capable of posting live data?

[Witek_M]

What's included in $4500 fix?

Does it have "Check Engine Light". Does it come on with key in position 2? Does it go off when engine starts?

[Pikes]

Originally Posted by Witek_M

What's included in $4500 fix?

Does it have "Check Engine Light". Does it come on with key in position 2? Does it go off when engine starts?

The check engine light does not light up with the key in position 2.
Its also not on with the engine running.
I had to look in the manual to see what it looks like.
All the other lights turn on with the key in position 2

[Pikes]

Originally Posted by FAR888

I agree with Loudgoldwing.

I think that the experts would require information like Long Term Fuel Trim and Short Term Fuel Trim.

Do you have a OBDII scanner capable of posting live data?

Thanks for responding.
What do you mean by" Long Term Fuel Trim and Short Term Fuel Trim" ?

I dont have a scanner, but I received a report from MB, they did the scan.

The list of misfire was in it (as in my first post)

The values for the two O2 sensors were:
Left O2 signal - 420mV
Right O2 signal - 600mV

According to test they were both in spec. The tolerances are from -200 to +1000 mV

MB did not give me a written qoute of the parts that needed to be fixed.
They called me on the phone while I was driving and the only thing that I can remember is catalytic converter/s(?)

The technician took the car for a drive and told me there was no problems when he drove it. I presume he did not drive it hard enough, because when I took the car home I had to stop and switch the engine off again to get rid of the "engine vibrations".

Ill go for another diagnostic scan if there is something else that you need.

Thats not too expensive - R250 (that`s about US$32)

Thanks again to all the people who responded

[FAR888]

Originally Posted by Petrusd

Thanks for responding.
What do you mean by" Long Term Fuel Trim and Short Term Fuel Trim" ?

I dont have a scanner, but I received a report from MB, they did the scan.

The list of misfire was in it (as in my first post)

The values for the two O2 sensors were:
Left O2 signal - 420mV
Right O2 signal - 600mV

According to test they were both in spec. The tolerances are from -200 to +1000 mV

MB did not give me a written qoute of the parts that needed to be fixed.
They called me on the phone while I was driving and the only thing that I can remember is catalytic converter/s(?)

The technician took the car for a drive and told me there was no problems when he drove it. I presume he did not drive it hard enough, because when I took the car home I had to stop and switch the engine off again to get rid of the "engine vibrations".

Ill go for another diagnostic scan if there is something else that you need.

Thats not too expensive - R250 (that`s about US$32)

Thanks again to all the people who responded

Hello Petrusd,

The experts will explain better but my basic understanding of it is:

Fuel trim refers to adjustments being made by the engine computer to get the proper ratio of fuel to air.

Short term fuel trim refers to adjustments being made in response to temporary conditions.

Long term fuel trim is used to compensate for issues that seem to be present over a much longer period.

Fuel trims are expressed in percentages; positive values indicate lean (add fuel) and negative values indicate rich (subtract fuel).

[Witek_M]

Originally Posted by Petrusd

The check engine light does not light up with the key in position 2.
Its also not on with the engine running.
I had to look in the manual to see what it looks like.
All the other lights turn on with the key in position 2

I asked those questions to help you understand that you have bought vehicle that has been doctored to hide existing problem.

Are you going to work on this vehicle yourself? If so you need to get yourself scanner that can display live data. At $32 per scan it will get expensive very quickly. To resolve this problem many scans will be needed.

[Pikes]

Is this the type of OBDII tool that I need?

Computers & Chips - ELM 327 USB diagnostic interface- supports hundreds of cars! top of the range! for sale in Cape Town

[crispy5974]

I know it's something of a catch-all but I'd be looking at the MAF as a priority. My ML430with 81k miles on it had similar rough idling and lacking acceleration symptoms as yours - which would go away with stopping and restarting the engine. The CEL light never came on and the codes in the engine were all the P03XX misfire ones plus a few others. I changed the MAF with a new genuine Bosch unit (avoiding cheap ebay fakes) and hey presto - problem completely gone.