when trying to accelerate hard, the car seems to knock (kicking?) but when I pull off the accelerator it drives normal. Is this bad gas- low octane. I filled with 92 octane from racetrack. wondering if they are selling poor quality gas or is this something more serious.

I experienced exactly the same thing. I strongly believe that they are selling the wrong type of gas. I change gas station and the problem went away. You can't never trust any merchant nowadays, ...they are all after for profit not customer service.

Try filling up with a premium gas like Shell V8 and add techron from Chevron. If that doesn't do it, it could be an antiknock sensor. In any case don't do a full throttle until it's back to normal. :rolleyes:

No knock sensor on his model. We could use a better description of the symptom.

Duke

The original post is 4 years old.

So I wonder how it got resurrected four years later.

Duke

Someone was probably doing a search on knocking. I was doing a search on 420SEL.

Since I ran across this thread, I am wondering, does the 85' W126 models have knock sensors? I am asking because it seems as if my car has a knocking type sound at lower RPMs under acceleration. If not, I am hoping it is simply the fact that I need to use higher octane fuels.

Thanks.

Nevermind my above post.... I did a closer search and found this thread. "M.B. Doc" stated the answer....

http://www.peachparts.com/shopforum/showthread.php?t=56966&highlight=knock+sensor

but then I searched and found this thread, with a TOTALLY different answer about knock sensors.

http://www.peachparts.com/shopforum/showthread.php?t=26804&highlight=knock+sensor

I hope it is not that my engine is simply worn out. :thinking: I never really worried about it before, but since I have been reading this, I am starting to think about it.

Someone said they had a 300E that did this and it ended up being worn cam lobes, but it only did it under moderate/heavy acceleration. Mine only does it at lower RPMs under light acceleration. It is very faint however, but I can still hear it and it concerns me. :( , but I refuse to spend $$$$ on this car, so I will keep on driving it, but easily.

Thanks.