Farting during overrun

[Deleted]

Further to the misfire and assorted electrical problems that have beset my car since an expert installed electronic ignition (posted under someone elses thread: "Misfire" - apologies, jimsbruv).....

It sometimes pops and farts on the overrun like a Morris Minor, which admittedly I can only hear on narrow lanes when I've got the windows open. It seems to happen at about 2500 revs, which is also the misfiring point when accelerating.

Guess I've got to do something else in addition to advice received from Phil and Enigmas.......check that I have actually got a 3 litre engine in there, and not a 948cc Series A lump

[enigmas]

It's running lean. Popping and farting as you've stated (especially on the over-run) is normally associated with lean running. Pull the choke on a bit when running at these speeds and conditions and note the changes. If things improve check that the float level is correct (it may be low) and that fuel delivery is as it should be to the carb (blocked filter...pump fuel flow incorrect?)


Here's a brief link and comment:
www.innovatemotorsports.com/forums/showthread.php?t=7182

[stantondavies]

Sounds like unburnt fuel in the exhaust, due no doubt to the misfire not allowing full combustion in the cylinder(s).
Does it ONLY happen c2500rpm? You normally expect misfire under load. Can be fuel starvation but I would put money on this being electrical. Have you replaced the plugs?

[Phil Nottingham]

Subject to checking all the above - it can be airleaks/holes in the exhaust, sticking or burnt exhaust valves or poor dizzy earth

[Deleted]

Thanks again, guys.

Stantondavies, it misfires under load between 2500 and 3500 revs. The popping on overrun seems to be at about the same range, but I can't be sure. I'll have to test it at different revs.

Cheers

[Phil Nottingham]

Try also switching to reserve pump to see if its that causing the problem