Miss firing ?

[Robbo]

Hi All

Right...its a 1975 2.25 petrol, with an unleaded head.
She starts lovely, ticks over lovely...but....under pressure, or going up through rev range, she misses quite a bit, no back firing just missing.

Oh and she's running on superunleaded - normally smoother for her! \:D/

Not had a chance to look at anything yet but suggestions welcome.
Cheers
Robbo - some say driver of Daisy...

[hobbit]

Try the electrics, plugs, points, condenser for a start, depending whenit was last done

Also are you using the oil bath filter, if so when was the oil last changes

First thing is though, have you done anything recently that might be causing this problem, if so start there

[Rich_P]

Does the engine splutter/misfire at standstill when revved?

EDIT:  Furthermore, is this happening when warm or cold?

[dew1911]

Miss Firing? I'm pretty sure she's a Spanish teacher at my old secondary school :lol:

[Robbo]

Does the engine splutter/misfire at standstill when revved?

EDIT:  Furthermore, is this happening when warm or cold?

seems to happen most of the time, obviously a little more when cold, but doesn't seem to go away when warm either.... :?

[Rich_P]

If it idles smooth, then first make sure all the HT cables are alright and everything is as it ought to be.  Then move onto the fuel mixture and timing.

It could be the main jet in the carb that's the problem, because when idling the engine is being fed fuel and air by the idler jet rather than the main jet.

[mark.yellow.series.3]

possible knackered dizzy?, but check the obvious first.

[MisterC]

Have you considered a fuel lift pump problem?  After checking the obvious electrical items of course.  I had similar problems on my 88.  Would tickover fine, but on load, occasionally, it would feel like it was cutting out/sturrer but then recover.  I put up with it for months, until it died on a roundabout in rush hour.  I have an inline fuel filter and that looked pretty dry.  If you have one of these they can cause vapour locks which could appear like a misfire.  If the fuel pump diaphragm is split or worn it would have enough suction to sustain tickover, but under load not enough petrol gets through.  Try priming it using the manual lever on the pump to see if fuel spurts out of the outlet (or check the inline filter if you have one).  I replaced the pump, and hey presto! fixed.  However, the radiator core blew yesterday and there appears to be a worldwide shortage of series radiators all of a sudden!  Anyone got a H/D 4 core one lying around?

[mark.yellow.series.3]

Have you considered a fuel lift pump problem?  After checking the obvious electrical items of course.  I had similar problems on my 88.  Would tickover fine, but on load, occasionally, it would feel like it was cutting out/sturrer but then recover.  I put up with it for months, until it died on a roundabout in rush hour.  I have an inline fuel filter and that looked pretty dry.  If you have one of these they can cause vapour locks which could appear like a misfire.  If the fuel pump diaphragm is split or worn it would have enough suction to sustain tickover, but under load not enough petrol gets through.  Try priming it using the manual lever on the pump to see if fuel spurts out of the outlet (or check the inline filter if you have one).  I replaced the pump, and hey presto! fixed.  However, the radiator core blew yesterday and there appears to be a worldwide shortage of series radiators all of a sudden!  Anyone got a H/D 4 core one lying around?

i have my old one if you want it, not sure if its a 4core or not, but your welcome to it.

[MisterC]

Thanks for the offer, but I've got one now.