Misfire @2000-3000rpm

[beu_79]

Evening all,
Experiencing a wierd misfire at 2000-3000rpm in any gear. It's repeating a split second loss in power but will go when throttle is increased, it's worse when not under heavy acceleration. Timing is fine, electronic ignition, sports coil both fitted.

If anyone has any ideas before I begin tinkering, i would be very grateful. It's a 1300 xflow, weber carb
cheers
Rich

[Luxobarge]

Hi - details of the car would help.....

[beu_79]

hahaha apologies, mk2 escort, 1300 ghia.

[JPB]

What type of ignition system is fitted? I ask because some Pertronix/Aldon "Ignitor" amp modules showed very similar symptoms during the R3W electronic ignition test cycle some four years ago, during which systems from a variety of makers were put to the test, one after another.

[pryantcc]

Hi - details of the car would help.....

It wouldn't help all of us Luxobarge! I would have no idea whatsoever regardless of the type of car!!

I do like the tip of looking at the engine in the dark when this is happening though to see if there are stray sparks "leaking" out somewhere. I guess that kind of issue wouldn't be related to the engine RPMs though.

Sorry for the useless post.....

[suffolkpete]

Try cleaning the idle jet. At light throttle openings it contributes quite a bit, up to 3000 or so rpm and a partial blockage can cause that sort of hesitation.

[spiderbloke]

Who you calling an Idle Get!!!!

Oh, sorry Pete, haven't got my reading glasses on

[richardtaylor]

Some good tips especially to check it in the dark - found faults this way myself before now.

When did it last have a set of plugs in it - could well be a plug breaking down under load or a ceramic insulator cracked?

[beu_79]

Cheers for all the advice! Had the carb apart yesterday and cleaned all the jets, had new plugs in 200miles ago, gap set recently. Engine rebuilt 500miles ago, sports coil, electronic ign. It's now almost a flat spot in acceleration. Could the electronic ignition be dodgy? I thought they were pretty fool proof.

Anyway, thanks again for all the tips. I'll keep on trying.

cheers

[JPB]

Tell us what make and model of ignition system it is and I'll copy and paste the relevant findings from the test report. None of them proved completely foolproof, some were more sensitive to the correct use of the thermal paste than others, for example.
I'd link to it but you need to be a member to read the threads on that board.