Car backfires

[Hernan]

My 1970 280SL backfires when in overrun and spits fire through the exhaust system, tail pipes.
Has anyone else counter this? if so what causes it and what how to repair it.
Thank you,

[Benz Dr.]

A leak in your exhaust system can cause this. 

[Hernan]

I have restored several 280 SL mostly body and paint, minor mechanical repairs but I can't figure how to fix this.
I would appreciate very much some guidelines of how to trace this leak.

[Bonnyboy]

I don't know about the fire out the ends of the exhaust but the first thing I would look at is timing.  If that is ok the pagoda exhausts have a tendency to get holes just after where the header pipes come together and allow exchange of gasses between the two lines.   If you put your fingers on top of that area you may find holes.  There should be enough room to put your fingers in there without dropping anything but be careful not to cut yourself if there are holes.   As a temporary fix you may try some muffler goop until it can be fixed properly to see if that stops your backfiring.  Check all of the connections in the exhaust as well for leaks. 

Also the obvious you should check that you don't have an aftermarket exhaust that is designed to do that. 

It worked for me.

[Nicolas Aristodemou]

I would look at timing and possibly misaligned vacuum pot attached to the throttle body. Does your car emissions control? Is it operational?

[David Robinson]

Mine stopped after I got the injectors cleaned and sorted the timing.

[Shvegel]

The correct distributor would be 062 (last 3 digits) and be a vacuum retard unit.  This should be connected from the outboard fitting on the throttle body and not the inboard one. It should also go through the vacuum switch just behind the battery.

Your US emission car should also shut off fuel when decelerating with the throttle released.  Something is amiss there.

[mauro12]

I Remember that my car was was backfiring and popping during deceleration . The sound was like a rally’s car . I solved the problem by repairing the csv that was leaking .