Need help identifying multiple cylinder misfire on left bank

Ken from Brunswick Technician Posted   Latest   Edited  
Question
Driveability
2001 Mercedes-Benz CLK430 4.3L (113.943) 5-spd (722.6)
P0305 - Cylinder 5 Misfire Detected
P0306 - Cylinder 6 Misfire Detected
P0307 - Cylinder 7 Misfire Detected
P0308 - Cylinder 8 Misfire Detected
Misfire
Misfire At Idle
Missing Under Load

This vehicle is misfiring and is setting misfire DTC's (EDIT from Skip Codes) on the left bank after short run from cold.

To date, we've replaced plugs and wires and a left side cat converter.

Fyi, I'm Jim Fox, Ken … is the shop owner. We're going to see if we can change the name on the account.

0

Chris from Commack

 

Diagnostician
 

Skip codes? Are we talking about misfire codes? If so, is it a hard miss?

+1

Bob from West Chicago

 

Mobile Technician
 

Can you give some information as to testing? Codes with definitions, at Idle or under load, Fuel trim etc

+2

Scott from Claremont

 

Manager
 

Hi Bob, 

I'm working with Jim (Ken) on getting more info. Thanks.

+1

Steve from Gainesville

 

Technical Support Specialist
 

If you are using the MB software there are some cool test procedures. The first one is the ability to monitor engine smooth running while either bank A or Bank B is shut down. Because the engine has two plugs/coils per cylinder a misfire can not be apparent when one circuit is failed and the other weak. Shutting off all the A plugs will increase the smooth running counts on a cylinder that was only running on the A bank. Doing the same with the B bank will test the other circuit.

A similar test is available under actuations for varying mixture and timing. Again while monitoring smooth running one is able to add or subtract fuel in 10% increments. Thus if one has an injector slightly plugged or a single cylinder vacuum leak one can reduce the smooth running value by adding fuel. If an injector is hanging open on a cylinder, reducing fuel by 30% (in 10% increments) might show a significant change in smooth running.

On some models one can also move the timing up on down. Not as valuable but I suppose if the individual timing control is off or for some reason the knock sensor has a particular cylinder so retarded that it affects smooth running, jacking the timing up can help in seeing this.

If the misfire occurs at cruise speed the lock up convertor sometimes is blamed. In SDS there is a function that temporarily shuts of lock-up until next key cycle. Driving with smooth running and monitoring before and after dropping lock-up can help.

The misfire situation also can be monitored by watching the smooth running values against the threshold values with SDS. This can help in evaluating what rpm/load range a misfire is occurring.

+4

Terry from Gillingham

 

Technician
 

Hi Ken Check your AirMass sensor this will throw these codes along with P0300.

0

Stacey from Brantford

 

Technician
 

Good Afternoon Steve

Can you expand on where in the xentry software the tcc disable function is located. Was chasing a vibration last week on a 2010 ML350 and could not find it?

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Steve from Gainesville

 

Technical Support Specialist
 

I would guess that would be under the activations menu in the trans Module. MB does move things around and some models like the ML have sometimes been slighted.

if there is a lock up function separate it could be hidden there.

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Stacey from Brantford

 

Technician
 

Thanks Steve

I looked pretty hard in the menus and did not see it. Vibration immediately goes away when you use the paddle shift to downshift. Pretty sure the converter has failed. It was a just purchased used vehicle so client was not real interested in extensive diag or repair time. Thanks again for the prepurchase advice on the xentry program. Still feel like a apprentice every time I get a chance to use it. But by far out of all my oem scan tools M/B did an excellent job with this software.

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Steven from Spokane

 

Mechanic
 

Hey Jim,

It's hard to tell what you are describing exactly, but from this part of your post, "...left bank after short run from cold". It sounds like it begins to happen after is warms up a bit from a cold start. Therefore, I would suggest that you have an oxygen sensor that has failed and the ECM is trying to use it for feedback when it goes into closed loop. Check the oxygen sensor on that bank.

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Steven from Spokane

 

Mechanic
 

Hey Ken, you got any more info to update us with? Did you get it figured out yet?

0