Multiple Cylinder Misfires - 2005 Mercedes-Benz CL65 AMG Long-Term Road Test

2005 Mercedes-Benz CL65 AMG: Multiple Cylinder Misfires

August 18, 2014

2005 Mercedes-Benz CL65 AMG

Our last update of the 2005 Mercedes-Benz CL65 ended with an all-too-familiar picture of the AMG parked in the service drive at the W.I. Simonson Mercedes-Benz dealership. I want to tell you it was back in action the next day. Or three days later. Or even ten. But I can't. That's because we didn't see it until 12 days after Mike dropped it off with a check-engine light. So what happened? The picture is part of the answer...

I'll get back to the lead photo shortly. First, let's take a detour through the dealership's approach to fixing the problem. When our car is dropped off, the dealer accepts a certain degree of liability. It has to report all of the issues found, regardless of severity, and we get that. In the case of our CL65, the list was extensive, and pricey.

We sifted through a quote of over $14,000 in items potentially needing attention before returning our focus to the problem at hand: the check-engine light. Our CEL displayed codes P2050, P2058, P205A, P2043, P2046, P204C, P204D, P204E, P204F, and P205C, according to the work order. This translated to misfires from multiple cylinders. A series of electrical tests narrowed it down to P2058 (cylinder 11 misfire) and P205A (cylinder 12 misfire).

Back to that lead photo. If you guessed it was an upside-down pan flute, pack your bags, you're headed home. It is actually the original ignition coil pack. All signs pointed to it as the root of our problem. Parts and labor were just shy of $2,200. While the coil was out, the tech replaced the spark plugs from the two cylinders in question.

2005 Mercedes-Benz CL65 AMG

The set of plugs on the right are from cylinder 11. If you're counting, yes, the CL65 has two per cylinder. Wear on these two could be considered typical for a 60,000-mile spark plug. It's the abnormal wear on the pair from cylinder 12 that raises a little concern. On that one plug in particular there appears to be extracurricular damage, but it's hard to know the cause at a glance. What we do know is that 6,500 miles ago the CL made gobs of power on the dyno. With the new coil and plugs, it's quick as ever, so it seems the problem was fixed.

2005 Mercedes-Benz CL65 AMG

Here is a close-up of the coil from the underside. There is evidence of activity unbefitting a spark plug in the left-most cylinders (11 and 12).

While the CL65 was at the shop waiting for parts to arrive, the dealer replaced a worn bracket for one of the ABC lines. It was done free of charge, since it was part of a prior repair performed by this shop.

Total cost: $2,199.44

Total days out of service: 12

Mike Schmidt, Vehicle Testing Manager 65,631 miles

2005 Mercedes-Benz CL-Class

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