Hi all, I would appreciate your input on my ongoing issue.
Vehicle stats: 2010, W204 C180 CGI with an M271 EVO Engine. 228 000km. Camchain, Sprockets, Tensioner and Expansion Plates were replaced by the MB Agents in Johannesburg in June 2016 at 147 837km. MB South Africa contributed toward the replacement due to the car having full service history with the agents.
Problem: About 8 months ago the car started to seemingly misfire/hesitate or oscillate as some mechanics have described it, at 2500 RPM and again at 3500 RPM when driving up inclines (gradual and relatively steep) in 4th and 5th gear (5 speed autobox). I have my doubts about the agents when it comes to diagnosing faults so I took the car to an Indy who opened it up and said that the chain had once again worn and required replacement (see Pics 1 and 2 below). I therefore took it back to the agents and put the diagnosis to them. Based on the photos they said there was no sign of wear on the sprockets and after keeping the car in for a couple of days, they came back to me saying that they had followed the manufacturers instructions and manually turned the engine over twice before measuring the chain. They maintain that there is no wear on the chain and that the engine is in spec. I have a signed letter from their workshop manager, on their letterhead with the bullet points below.
We have taken off the tappet cover and inspected the camshaft gears and timing chain for any wear.
The engine timing is in spec and there is no wear on the timing chain.
We have taken out the intake manifold to inspect and we have found the intake valves has carbon.
Possible cause could be worn valve stem seals or over fuelling injectors.
As agreed we are charging out three tins of fuel additives to be used over the next three fuel tanks filled.
The agent's diagnosis is that there is a carbon buildup in the engine which is causing the hesitation (Pics 3 to 7). They sent their own photographs of the chain and sprockets (Pics 8 to 10). Their remedy was to remove the head and have it machined and then replace the valves, valve seals and see what happens. For this they quoted R75 000 while the vehicle is now only worth about R80 000. Their remedy made no financial sense.
I took the car to another Indy who specializes in removing carbon deposits by blasting with walnut husks while the head is in place. He said straight out that blaming the carbon for the symptoms I am experiencing is taking a shot in the dark. He said he was willing to charge me to do the work but didn't see a point since in his opinion it would not work. He connected his computer the car and we went for a drive. He said he could definitely feel a misfire and while there were no error messages, it may have been due to the plugs or coils only starting to die. He gave me the part numbers and said that I could source the parts myself, which I did (Beru coils and NGK plugs) and he fitted same for me. The problem however still persists. He, like the agent then suggested Fuel Additive in case one of the injectors was blocked. We have gone through three bottles of MB Fuel Additive and another produced by a company called NOS. I have also made a point to fill up with Calex with Techron. I am also aware however that these cleaners are not going to have much effect cleaning carbon deposits from a direct injection engine.
I am getting rather worried about the situation and certainly don't want the engine to pack up. I have lost a W203 due to the camchain having skipped and fear that the agents may not have diagnosed the situation correctly. I have spoken to a mate who builds Subarus for rally and he reports an incident similar in symptoms on one of his Subarus was due to a dying camshaft position sensor. It was not registering an error.
That was quite a complex issue, especially with the varying diagnosis from the shops. It was unfortunate no one here was able to help, but it is good to know that the Walnut blasting solved the problem.
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