Hi. My 2L pinto on twin dellorto carbs isn't running great. Absolutely fine pootling about, but if you flog it for a few minutes, it starts to misfire. Sounds like overfuelling, backfiring, missing a cylinder, but fine if you keep the revs high - which makes it progressively worse when you do go back to low revs. Any ideas what causes this? I really can't be arsed with an engine that needs tuning every year!

Thanks.

check the fuel filter

quote:

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Originally posted by gremlin1234
check the fuel filter

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and if you haven't done already top the fuel tank up.

Nothing obvious in the fuel filter and it had already had a full tank of fresh weeks ago. I made a point of not letting it stand excessively, because it died for 7 years last time I left it all winter!

Very tempted to fit a zx12 engine, but the pinto is such a suitable engine for these cars. When it runs right....

I've given it a ludicrous dose of petrol treatment. Also had to lift the mother in law out of it today lol, but at least she loved it!

It's also sounding quite tappety despite having fresh oil to a good level. Could a jumped timing tooth cause this sort of problem?

It might sound a silly reply, but, Try changing the rotor arm (there is a resistor buried in it between centre and tip) also, if it has points make sure the the little thin plastic strip between the rivet and the heel (that opens and closes the points) is not flexing and allowing random points gap when hot.
After that I would look at a hot breakdown of the ignition leads (hold one when running, if you get a jolt then a faulty lead), then after that I would start looking at the ignition module.
JMHO

Check the jets in the carbs is it twin side carbs or down draft

Start with checking the basics , compression ,check and adjust the tappets/ inspect the cam for wear while you’re at it, unlikely to be a jumped tooth but not impossible so worth checking . Also check the distributor advance/ retard is working correctly, Bosche distributors in particular can and do seize , if fitted with points probably worth fitting new along with the condenser. Motorcraft distributor it’s worth fitting a small lead between the points screw and the baseplate securing screw to cut down voltage drop , for what they cost a rotor , cap and leads before checking and adjusting the timing . If electronic it could possibly be the module or if aftermarket it could very well be your problem? Carb(s) should be the last thing to check and adjust when tuning an engine