OK, I need some help on diagnosis
11-15-2013, 06:41 PM
#1
OK, I need some help on diagnosis
I have a 90 300SEL with 145,000 klm so that is 90,000 miles. Car works perfect. Today I passed a car on the highway and kicked her down. When I got home she was "missing" on one cylinder so it seems. Checked compression on all. Good, Fire on all. Good. It has new cap, button, wires and plugs less than 300 miles ago. I can hear a "clatter" or "clicking" in the front of the engine. I also noticed a cable from the ICM on the fender is sheared off but someone said that would not cause a misfire. I am not sure how long it has been like that. I put my stethoscope on it when the car is running and I can hear a loud banging on the other end of it. So, I am thinking Timing Chain or tensioner maybe? Would that put it enough out of time to miss?
11-17-2013, 10:34 AM
#2
Junior Member
Is there any fowling on the spark plug in the cylinder in question? which end is the "other end"?
Ryan
Ryan
11-18-2013, 01:36 PM
#4
Junior Member
I'd double check Oil VISCOSITY ...
If your Summer Weight Oil is too thin, Hyd Lifters can clatter & fail to provide enough lift, & the results CAN be what you're experiencing ... I do have the Svc Man, but will need more/other info to discern more specific info ... Pls get a (good) pic of the mysterious "cable from the ICM on the fender is sheared off" so I/we can make a determination of it's applicability ... PM if you wish to ...
I have a 90 300SEL with 145,000 klm so that is 90,000 miles. Car works perfect. Today I passed a car on the highway and kicked her down. When I got home she was "missing" on one cylinder so it seems. Checked compression on all. Good, Fire on all. Good. It has new cap, button, wires and plugs less than 300 miles ago. I can hear a "clatter" or "clicking" in the front of the engine. I also noticed a cable from the ICM on the fender is sheared off but someone said that would not cause a misfire. I am not sure how long it has been like that. I put my stethoscope on it when the car is running and I can hear a loud banging on the other end of it. So, I am thinking Timing Chain or tensioner maybe? Would that put it enough out of time to miss?
11-18-2013, 02:04 PM
#5
No it is nothing like that. It was a sudden thing after passing the truck, One minute perfect and next not. The cable is from the ICM and runs and plugs in by the water pump.
11-18-2013, 02:40 PM
#6
Junior Member
Ok; Next Step is ...
I was taught (in 1960) to "read the plugs", so pull them CAREFULLY arranging them by Cylinder Number. Normal coloration should be slightly to medium Tan, & clear/clear of carbon or other deposits. Anything different than the stated "Norm" tells Us something to extrapolate from ... RSVP when they're out & have been examined. Lemme see; I think I have the M117 firing order chart here somewhere ...
[URL="http://www.autotrend.us/mercedestuneupv8.htm"]
[URL="http://www.autotrend.us/mercedestuneupv8.htm"]
Last edited by Tony Funches; 11-18-2013 at 02:43 PM. Reason: image did not load correctly
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02-21-2014, 01:07 AM
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Wow, good 'catch' on the harmonic dampner separation issue! Hope you were able to catch that before anything serious resulted! I was ready to vote for the timing chain issue. That said, would like to suggest double checking the timing chain stretch anyway just for good measure. Mileage is getting pretty close to time to check it for preventive measures. I'm not 'up to speed' on the six in your car, I do know the 420/560 V8's have a tendency to require the plastic timing chain guides replaced periodically also (same time as the timing chain!) as they will get brittle, break, then the timing chain will have room to "whip around", possibly hop timing. Bent valves are a certainty then! Probably make some alarming sounds at the very least, I'd think!
