Back firing not starting

[Buffers]

Hi All. Can anyone help. My 1987 1.9 petrol T25 starts OK then once its running for a few miles it starts missing a beat and sounds like its back firing. Call the RAC and they said it could be the coil, fuel pump or the black module which looks like its been changed before. The garage where It has gone to said it could be dirty fuel in the carb. Any suggestions would be appreciated. Thanks Phil

[Moonrakers]

All the above could well be to blame, as well as plugs and leads, filters, vacuum pipes to carb, ignition switch failing and timimg.

None of these things are particularly expensive or difficult to amend, all basic diy stuff luckily. Start with the simplest thing, check the fuel filter and change if it's old, inspect the tiny cone filter that you'll find in the fuel inlet of the carb (take the hose from the fuel pump off and gently extract the little filter with a screw). Clean the carb by using an aerosol carb cleaner as per instructions. Buy a meter of vacuum line from Brickwerks or wherever and cut a couple of lengths to replace the short hoses from the carb as pinprick holes letting air in can easily cause your symptoms - very common.

After that, check the fuel pump is delivering fuel (lots of threads about pumps on here) or just buy a new one - they are very easy to fit (make sure you replace the rod below it as they shorten with wear). You can test the coil yourself - again, there are threads to tell you how. The module you mention - ignition amplifier - could be duff even if it has been replaced before. They are not expensive.

Good luck, I'm sure you'll fix it soon enough. When my motor developed a backfire I just replaced all the components above in one go including leads with the metal shrouds removed as per instructions on here to avoid shorts and it's been sweet as a nut since, though I didn't get to discover exactly what was causing the fault.

[kevtherev]

Your symptoms are indicative of a weak mixture after the choke is off.
As suggested above plus all the other items that require vacuum should be suspect including any gaskets.
Be methodical in eliminating the suspects