on my '88 300e, after heating up to operating temperature and after a long highway run, im noticing that there sounds like a knocking from the engine during deceleration and at idle. Theres no knocking at all at startup or in short hop city hauls.

is this normal

USE 91+ OCTANE. ON MY 300E, W/ 87 OCTANE i CAN ACCELERATE TO 70 MPH UPHILL W/ KICKDOWN. W/ 91 OCTANE, I HAVE GONE TO 115 UPHILL W/ KICKDOWN. CHECK YOUR SPARK PLUGS, MAYBE YOUR ENGINE IS MISFIRING.

an interesting suggestion; i have also removed that resistor that retards the spark; i regularly use 93 octane. ill try either replacing the resistor or puttng octane booster in the tank to determine if its a spark issue.

I would suggest replacing the resistor first. I removed the resistor from my '88 260e and at first I thought it performed a little better but after a week or two, I noticed that it misfired slightly when idling, something it had never done before. It also was bogging down when driven with a cold engine. I replaced the resistor and it's back to normal.

I don't think my problem was gasoline related because I always use 91 octane from the same station.