1987 300E, w/ 209k miles. When it's hot and I'm accelerating away from a stop, there's a rattling/pinging sound coming from the right passenger footwell. (well, that's where it sounds like it's coming from) Did these engines have anti-knock sensors, or is what I'm hearing engine knock?

anthony

Only the multi-valve engines have KNOCK sensors that allow the ignition system to retard timing. Sounds like you engine needs higher octane fuel!!

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The 300e also creats lots of carbon from the oil getting by the valve guide seals. This carbon can change the effective compression ratio and increase the octane rating necessary. A good decarbonizing treatment often can solve this if you are using an appropriate fuel.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Thanks for the information. I'm using 92 octane Chevron gas, so it's not the octane rating. Any recommendations on a decarbonizing agent? Also, does running the engine at high rpm's help in clearing out the deposits?

thanks,
anthony

Hi Anthony:

I am having the same symptoms as you are with my 87 260E. I have tried retarding the timing, different premium fuels (Shell, Chevron, Arco and Union 76), octane boosters and still can't get rid of my noise.

It doesn't seem like I have any power loss either. It is just a annoying sound while driving.

If I solve my problem or you solve yours, please let me know and I will do the same.

Aloha,
Eric

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1987 260E Charcoal Grey 157,000 Miles
1987 260E Forest Green 120,000 Miles

Hi Anthony:

Check my post.

Knocking Solved. What was that Sound???

Aloha,
Eric

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1987 260E Charcoal Grey 157,000 Miles
1987 260E Forest Green 120,000 Miles