Backfiring 280SL

[n/a]

We have a 280SL 1968. It has been recently rebuilt, motor, body etc..... Drives great BUT  It has a nasty habit of doing severe loud back fires. Also when you 'gun' it to pass someone or just to get up to speed it coughs and chokes, does some banging etc. But the woorst is when you are taking your foot off the gas pedal it lets out some pretty large back fires, scares the h*** out of people. Can I get some ideas on fixing this please?

[jeffc280sl]

Please tell us if your 280SL is a US or Euro version and your type of transmission (manual/automatic).  The problem could be a number of things including that US versions came with some emission control devices that may cause problems.

Jeff C.
1970 280SL 4-speed

[rwmastel]

Zurmac,

Hi.  Read these threads and see if they give you some ideas.

http://index.php?topic=4732
http://index.php?topic=4426
http://index.php?topic=3216
http://index.php?topic=2608
http://index.php?topic=247

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[n/a]

For Jeff,

Car was shipped to Canada as new in 1968. HAs been totally rebuilt in Switzerland where it now resides. We have owned the car for some 30 years, second owner. The manual doesn't talk about any emission controls.

[Raymond]

There is a lot of reading in the posts that Rodd suggests, but they are worth the reading.  

My first thought is that the fuel/air mixture is too lean.  Check that the linkages are exactly right, the timing is correct, and the vacuum advance is working.  If all that is correct, and the symptoms remain just as you described, remove a shim from the Warm Running Device to enrich the mixture a tad.

Ray
'68 280SL 4-spd Coupe

[Randy Woodward]

Jeff, do you still have your 70 280sl 4-speed? I just got one and I'm getting a little frustrated already with the back-firing issues. It's still early, but I'm just looking for some hints. I have the exact same car as you. My BIG problem is at 3000rpm or more, where I get huge back-fires. Just little ones on decel at 2500rpm, but runs pretty darn smooth otherwise at 2500rpm. Any suggestions?

quote:Originally posted by jeffc280sl

Please tell us if your 280SL is a US or Euro version and your type of transmission (manual/automatic).  The problem could be a number of things including that US versions came with some emission control devices that may cause problems.

Jeff C.
1970 280SL 4-speed

[Randy Woodward]

Jeff, do you still have your 70 280sl 4-speed? I just got one and I'm getting a little frustrated already with the back-firing issues. It's still early, but I'm just looking for some hints. I have the exact same car as you. My BIG problem is at 3000rpm or more, where I get huge back-fires. Just little ones on decel at 2500rpm, but runs pretty darn smooth otherwise at 2500rpm. Any suggestions?

quote:Originally posted by jeffc280sl

Please tell us if your 280SL is a US or Euro version and your type of transmission (manual/automatic).  The problem could be a number of things including that US versions came with some emission control devices that may cause problems.

Jeff C.
1970 280SL 4-speed