OM642 - Engine stumbles/dies on hard acceleration

[ctjfb]

Firstly - This post is about an issue with a Jeep Commander CRD, and not a Merc - But I do have a Merc, and it is a Mercedes engine

I have an intermittent problem with the engine. Sometimes when accelerating hard, or reasonably hard, then engine will very badly stumble - just cuts out for a moment and then resumes - it can do this several times in a few seconds, and always recovers if I back off the throttle. It may then repeat this right away if I accelerate again, or just behave itself for a while.

A couple of times recently when I floored it from standing, it completely died at around 3k revs and did not recover at all until I backed the throttle right off.

Also - when it is misbehaving and I quickly accelerate & back off there is a strange noise as I back off. It's a little like those turbo dump valves that some folks fit to modded cars but not nearly so loud or obvious ...

Needless to say - no fault codes at all, and it starts, and runs, absolutely fine when it's not misbehaving ..

Engine has done 110k miles with good service history

Any thoughts ?

Chris

 

[Doug1234]

Have a search for posts made by me last June /July /maybe some in August.. I had this on my 06 Grand Cherokee which is exactly the same as Commander apart from body work.
But to generalise mine did this at just over 2k revs and did exactly same as yours.
Best option for you to do is get it on live data and drive it and monitor turbo / boost pressures and actuator.
My experience says you will get egr codes but these are only because air flow through engine is wrong when its stuttering and ecu throws egr code up.
I have a code reader so I could monitor and clear codes on mine ( icarcsoft bcii) .
My turbo had vanes that were sticking / exhaust manifold broken up internally so basically vanes could only work to a certain limit.
My main code (stored) was p0046 turbo actuator and this was because it could not work the sticking /stuck vanes.
So concentrate on using live data to monitor actuator and turbo.
And just remember it will keep chucking up egr valve code p0403 (icarsoft ) and p0404 with generic readers but in my case egr is good .. nothing wrong with it .. codes put up because of airflow being wrong.
So live data and monitor turbo actuator and check turbo linkage /operation.

 

[mattkh]

And just remember it will keep chucking up egr valve code p0403 (icarsoft ) and p0404 with generic readers but in my case egr is good .. nothing wrong with it .

Thanks for a very informative reply.
Did you remove the EGR valve to check how clean it was or it was working as it should ? If not, how did you arrive at the decision that 'nothing wrong with it'.

 

[Doug1234]

Egr was removed and was clean with lightest covering if soot.
Egr code would flag up after long period of engjne idling and moving in traffic stop go etc, accompanied by a slight hissing and the p0403 code.
I could make it stutter at will by trying to exceed 2k revs , had to drive slowly and not push it hard and also had to help it change gear by shifting manually .when it first started doing this it was between 3-4 gear change at 3.5k revs … slowed up /held revs / seemed to climb through a hole and then charge off again… other than that all normal until trying to use 3.5k revs.
No high or low boost codes , plenty of diff and transfer case codes as the QD2 4wd did not like what was going on.
Once it got so it was only 2k revs max then the lightning bolt on dash would come on . Drove it for months like this as working non stop, just resetting egr code now and then. Only ever put main engine warning light on about twice.
I fitted exchange turbo from ACP at Milton Keynes and all good now, back to normal trying to lift front wheels off the ground when floored.
Do use live data to narrow your fault down, its exactly what mine did but yours could be actuator faulty.

 

[ctjfb]

Have a search for posts made by me last June /July /maybe some in August.. I had this on my 06 Grand Cherokee which is exactly the same as Commander apart from body work.
But to generalise mine did this at just over 2k revs and did exactly same as yours.
Best option for you to do is get it on live data and drive it and monitor turbo / boost pressures and actuator.
My experience says you will get egr codes but these are only because air flow through engine is wrong when its stuttering and ecu throws egr code up.
I have a code reader so I could monitor and clear codes on mine ( icarcsoft bcii) .
My turbo had vanes that were sticking / exhaust manifold broken up internally so basically vanes could only work to a certain limit.
My main code (stored) was p0046 turbo actuator and this was because it could not work the sticking /stuck vanes.
So concentrate on using live data to monitor actuator and turbo.
And just remember it will keep chucking up egr valve code p0403 (icarsoft ) and p0404 with generic readers but in my case egr is good .. nothing wrong with it .. codes put up because of airflow being wrong.
So live data and monitor turbo actuator and check turbo linkage /operation.

Many thanks for your reply and suggestions

I have checked the turbo actuator and it moves normally thought the full range. I also disconnected the linkage and the actuating rod moves very freely without any signs of binding .. I did this with engine cold and 'warm' but not red hot

I'm getting no codes whatsoever ... I'm using Appcar DiagFCA which doesn't miss much normally! I will try to monitor some live values if I can find someone to assist whilst driving!

Again - thanks for your inputs.

Chris

 

[Doug1234]

Your on the right track then , App car diag is fantastic bit of kit