D

David Pettengell

Member
So my 1984 series 3 has a backfire under deceleration. I thought it was that I had exhaust leaks but they are all eradicated but still popping.

Seems to be when you take the foot off the gas and its decelerating. Any ideas?
 
Engine running to rich and or timing retarded to much.Other possible causes are exhaust valve not sealing,dizzy worn.
 
More likely a dirty idle jet. What carb do you have? If it's a Weber the idle jet is at the engine side of the carb. Unscrew carefully and give it a clean. Blow through to get out any carbon or crud and refit.
 
My series 3 started doing this shortly after I bought it and started using it properly. I guessed at naff exhaust valves cos It was not converted to lead free petrol. I started using the additive (more than recommended on the bottle) and after a couple of hundred miles it stopped popping and backfiring and has been ok since. Could have been crap in the carb or crap on the exhaust valve seat, I don't know but it's fine now.

Col
 
Colthebrummie said:
My series 3 started doing this shortly after I bought it and started using it properly. I guessed at naff exhaust valves cos It was not converted to lead free petrol. I started using the additive (more than recommended on the bottle) and after a couple of hundred miles it stopped popping and backfiring and has been ok since. Could have been crap in the carb or crap on the exhaust valve seat, I don't know but it's fine now.

Col
Click to expand...

If it's been standing could be carbon build up or sticking valves ... even the varnishy stuff in the carb, (petrol residue) ...
 
John S said:
More likely a dirty idle jet. What carb do you have? If it's a Weber the idle jet is at the engine side of the carb. Unscrew carefully and give it a clean. Blow through to get out any carbon or crud and refit.
Click to expand...
How easy is it to clean idle jets? Can you literally unscrew them and give them a clean and replace? Or do you have to take apart the carb/ drain all full, etc. to do this. Thanks
 
thspeller said:
How easy is it to clean idle jets? Can you literally unscrew them and give them a clean and replace? Or do you have to take apart the carb/ drain all full, etc. to do this. Thanks
Click to expand...

What carb do you have ?

If you're going to strip it you'll need a gasket set for it... easy to get tho

And the web is full of info and vids ...
 
Dippypud said:
What carb do you have ?

If you're going to strip it you'll need a gasket set for it... easy to get tho

And the web is full of info and vids ...
Click to expand...

Weber 34 ich - I got the impression from people’s description that you could just unscrew, clean and out back without draining/removing/rebuilding. Is that correct?
 
Yes, on the Weber 34ICH you can just unscrew the idle jet, give it a blast with some carb cleaner or compressed air and put it back. The idle jet has an O-ring, so have a look at that as well - if it's worn or brittle it's probably time to overhaul the carb.
 
Sorry for the radio silence, had a log in problem . As posted just carefully unscrew , wipe clean and refit. Hi
 
Thanks - was easy to do and problem sorted. I’d not used it for a month and I think fuel had got a bit sticky. Now adding additive as gather that can help. Tom
 
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