Mercedes CLS 350 CGI Cylinder 5 Misfire

[catalzzy]

Hello,

The car has started to misfire cylinder 5 and sometimes cylinder 1 but that usually goes away for cylinder 1. Cylinder 5 has new coil plug and new spark plug. Weird thing is when clear fault code and the car stopped misfiring on idle. I have test driven and when it reach above 2k it will start to misfire a little when i bring to stop. I suspect is the o2 sensor or MAF sesnor even worse the fuel injector could be a culprit. No coloured smoke coming from the exhaust.

Then I have dived into to check the spark plug and fuel injector and cleaned the maf and throttle body. TBH CGI is quite hard to remove certain parts. I still get misfire on cylinder 5 and i checked intake manifold which is single flap type. The mbar is 380 and when i rev up to 2k then let go the mbar dropped to 180 then it shudders before it becomes smooth. same thing other way if i rev to 2k rpm then i can feel a bit shuddering and mbar dropped to around 200. I was suspecting the intake mainfold with huge carbon pile up on the valves around cylinder 5. Here are the photos i have investigated.

 

[catalzzy]

Hi is this compression ok?

 

[ajlsl600]

I wud say not. What are the results for other cylinders. Have throttle in same position for test on all cylinders.

 

[catalzzy]

I only tested clyinder 5 because its misfire related. And all i did was start the car and turn off. Didnt rev and left to idle for few secs.

 

[ajlsl600]

OK... normally compression test is done by disabling a start. Remove plugs, screw in tester crank motor , I use half throttle to ensure air flow, crank a predetermined time, say 20 sec. Repeat for all cyl, compare with specc. 125 psi is in my view low.. general idea achieved by comparing with all other cylinders.
I have a piston aircraft system in which you charge the cyl with compressed air and check with piston at top and bottom of cyl gives a better pic of bore/ring health.
Forgot to add, and you will hear air passing valves, should that be happening

 

[catalzzy]

I have taken your advice for giving some throttle response for cylinder 5. I couldnt take out the other coil plug wires as they are really hard to get out. Now i am stuck with compressor adapter in cylinder 5.

Please advice what ideal tool from hardware shop to customise to take the plug out eg using bathroom crooked wrench?

How can i take out the compressor tester adapter out? I spent hours trying ideas how to take out eg using rubberend stick, superglue, using my finger to move etc