Backfire on 280s
 

This morning while driving in my w116 280s, i used the kickdown, while driving at about 35mph, the tranny shifted to 3rd, but the engine backfired through the carb once, it run fine after that, and also on subsequent kickdowns it never backfired again.

i know of backfire through the exhuast, but not the carburettor, what can cuase this.

Sounds like ignition timing, could be vacuum advance working overtime.

Man, that brought back great memories of playing around in a 1969 VW Beetle I had 20+ years ago...get on the gas hard, then jump off the throttle, it would let off one heck of a bang through the exhaust. It seemed like lots of fun to a bunch of drunk 16 year olds at the time...guess ya had to be there.

Improper secondary spring adjustment ,accelerator pump mis -adjusted or leaking are a few things that come to mind as well as the egr valve defective or could have just been a while since you opened her up and she coughed on the first try .....

Frontfire
 

I'm with Dog and Iva - over-pulling vac advance due to weakening springs, or possibly momentary loss of countering vac retard, if your distributor has both.
First check vac connections - if loose, can clip off just a little (like 1/4 in) and usually get a tight fit again; also possibly lube distributor plates - especially indicated by a momentary, non-repeating event.
Check static (no vacuum connected) timing and then with each (adv and retard, if equipped) at factory settings.
On the other hand...if it hasn't repeated...
Happy troubleshooting.
Stan

Ignition Timing W116 280s
 

CAN SOMEONE PLEASE TELL ME WHAT THE CORRECT IGNITION TIMING IS FOR THIS VEHICLE WITH ADVANCE DISCONNECTED AS WELL AS CONNECTED.

AT FULL THROTTLE THE CAR PRE IGNITIES (PINGS) IF I RETARD THE IGNITION TIMING THE CAR SURGES, IAM PLAYING AROUND WITHOUT A TIMING LIGHT, BUT I JUST GOT A TIMING LIGHT, NOW I NEED THE COORECT SETTINGS

WHAT IS THE PROCEDURE FOR SETTING TIMING? DOES ALTITUDE MAKE DIFFRENCE TO THE SETTINGS, PLEASE HELP!!:confused: