Need some advice: engine has a misfire on cylinder #1 that I cannot resolve. 2000 SL2 5spd, not the original motor to the car ...

[SixthSphere.com]

Need some advice: engine has a misfire on cylinder Home that I cannot resolve.



2000 SL2 5spd, not the original motor to the car but has been solid with no issues or heavy oil use for the last 50k miles. Car consistently gets 36-38 mpg. Now I’m seeing 27-30 mpg and a loss of power.



Been running 5w30 full synthetic oil with services every 4K miles.



I checked the spark plug, it was wet and dirty. The others are nice. The piston is also wet. Exhaust smells rich but isn’t blowing smoke.



I swapped plugs, no change.

I swapped wires, no change.

I swapped coil packs, no change.

I swapped the ignition module, no change.



I cleaned the grounds and terminals on the ignition module and coil.



I have good spark at the cylinder. I replaced the fuel injector with another from a good running engine, no change. The fuel filter was replaced 600 miles ago.



I troubleshooted based on basic knowledge and from the factory service manual. What else am I missing??





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[leighv]

do a compression test.

[ultraviolet]

do a compression test.

i was gonna say the same thing, sounds like a burned valve. been there, done that.

[leighv]

i'm betting money on a waxed piston. maybe we'll get some carnage pics haha