Om642 jerks at stable rpm's

[Gurkus]

Hello, I have chrysler 300c 3.0crd, which has om642 160kw mercedes engine. Had the engine replaced and now i get p0403 fault after the engine warms up and is kept at stable rpm's, no matter what's the speed. Acceleration is good, no jerking, but it seems to jerk just a little bit when you keep stable rpm's, for example - in cruise 95km/h, it jerks a bit and after like 30sec the lighting bolt warning comes up and the engine loses all power. Started to change all the sensors, fuel regulator, sensor, fuel regulator in fuel pump, egr pressure sensor, changed egr itself, turbo actuator, o2 sensors. Fault doesnt come up if i hard accelerate when the jerk starts, but if i ignore the jerk, fault comes up after 30sec.

 

[Doug1234]

The fault code p0403 is an egr code.
Now I have a Jeep grand Cherokee 3.0crd 2006 and when I had issues I had p0404 (egr) on my icarsoft bcii on the Chrysler / Jeep reading side of the diagnostics but on the generic obd reading side it would show the p0403… so a specific Jeep reader will give you more detail code wise.
The fault I had was turbo vanes sticking due to bits of broken exhaust manifold , wouldn't rev over about 2200rpm or thereabouts without big hiccups but I drove it for around six months or more during lockdown to get to work until fitting another turbo and nothing wrong with my egr .. just airflow across engine making ecu unhappy.
So you have an egr code but it can and will pop this up due to other airflow issues be it inlet side or exhaust related .. it’s a Chrysler and they do odd stuff .. it also will not give you codes for bad injectors neither.. it’s a Chrysler thing because the software is Mercedes derived it being a Mercedes engine .

I would suggest fitting a resistor to rule out the swirl flap motor as this will cause the issue you have and explain why it comes and goes , and secondly did you get the replacements engines injectors coded to the ecu ? .. fitted six new to mine and it ran like a bag of old spanners until they were coded in.. if you unplug an injector on these om642’s in these jeeps or Chryslers then run the engine with one unplugged the coding for that cylinder defaults to AAAAEE .

Mine was showing the AAAAEE and I never ran it with any unplugged only fitted six new but it still defaulted ?.
On my code reader mine will tick over at 620 rpm and it’s very well behaved not going much more than +/-25rpm either side of that

 

[ajlsl600]

That's a bgr most injector I get involved with will run on stored codes often pretty well they just run optimum when coded in. I had a few Hitachi that did same.

 

[Gurkus]

The fault code p0403 is an egr code.
Now I have a Jeep grand Cherokee 3.0crd 2006 and when I had issues I had p0404 (egr) on my icarsoft bcii on the Chrysler / Jeep reading side of the diagnostics but on the generic obd reading side it would show the p0403… so a specific Jeep reader will give you more detail code wise.
The fault I had was turbo vanes sticking due to bits of broken exhaust manifold , wouldn't rev over about 2200rpm or thereabouts without big hiccups but I drove it for around six months or more during lockdown to get to work until fitting another turbo and nothing wrong with my egr .. just airflow across engine making ecu unhappy.
So you have an egr code but it can and will pop this up due to other airflow issues be it inlet side or exhaust related .. it’s a Chrysler and they do odd stuff .. it also will not give you codes for bad injectors neither.. it’s a Chrysler thing because the software is Mercedes derived it being a Mercedes engine .

I would suggest fitting a resistor to rule out the swirl flap motor as this will cause the issue you have and explain why it comes and goes , and secondly did you get the replacements engines injectors coded to the ecu ? .. fitted six new to mine and it ran like a bag of old spanners until they were coded in.. if you unplug an injector on these om642’s in these jeeps or Chryslers then run the engine with one unplugged the coding for that cylinder defaults to AAAAEE .

Mine was showing the AAAAEE and I never ran it with any unplugged only fitted six new but it still defaulted ?.
On my code reader mine will tick over at 620 rpm and it’s very well behaved not going much more than +/-25rpm either side of that

I have already fitted a resistor in a swirl flap cable. And yes, i have coded the new injectors to my ecu, bosch diagnostics shows good balance and flow through these injectors, tested fuel return amount on injectors, they seemed very good, also, engine sounds very purely and quietly, much much quiter than the first one(the crankshaft broke in half, literally. Everything else is good so i have lots of parts). The problem only comes up if i keep stable rpm's, if i hard accelerate when it starts to jerk - there is no mistake. Bosch diagnostics showed p0403 as well

 

[ajlsl600]

That's, an engine stutter you refer to or a drive line jerking.

 

[Wighty]

I have already fitted a resistor in a swirl flap cable. And yes, i have coded the new injectors to my ecu, bosch diagnostics shows good balance and flow through these injectors, tested fuel return amount on injectors, they seemed very good, also, engine sounds very purely and quietly, much much quiter than the first one(the crankshaft broke in half, literally. Everything else is good so i have lots of parts). The problem only comes up if i keep stable rpm's, if i hard accelerate when it starts to jerk - there is no mistake. Bosch diagnostics showed p0403 as well

Might be a blocked exhaust back pressure sensor , the small hole underneath gets clogged .
Take the turbo actuator off , spray clean any carbon gunk out with electrical cleaner and put a tiny amount of high temp grease on the worm gear inside . Also check the (4?) small wires that are on the outside of the pcb board inside , they can be small breaks/cracks in them .( Edit…just seen you changed the actuator )
Both free jobs .
The exhaust bps,egr,inlet port motor and actuator all share the same 15amp fuse .

 

[Gurkus]

I tied the second spare egr to the engine and plugged it in. No mistakes now and no jerking at all, but this is not a real fix. Changed the camshaft sensor, high pressure fuel pump, engine speed sensor. But still nothing seems to work...