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Mario79

Poor running when warm

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Hopefully some one can help me. I have a 1979 S2, runs great when cold and probably for the first 10 mins, then as soon as the car is warm it starts to run rough when slowly moving off or accelerating away from a low gear it misses and jerks. When the car is revving high its fine. Any ideas? Thanks

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Sounds like over-rich fuel mixture.

Have you checked the plugs - are they black? If you use the choke (and there's no real reason you should), is the cable getting stuck, and not returning properly?

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Check the slow running jets in the carbs..they cover the progression too, up to when the main jets chime in. Also look at the progression holes which are uncovered by the throttle butterflies rotating. Modern fuels leave varnish like deposits and restrict the flow...this causes the sort of symptoms you describe. The restriction can be less than obvious as the jets are on the small side of the range that would be suitable, so a very small reduction in hole diameter and thus flow rate can have an inordinate effect.

 

Having said that, most troubles actually turn out to be ignition based!!

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Thanks for the replies, plugs look ok, choke not stuck on. Hav'nt checked the carbs yet, would a faulty coil cause the same symptoms ?

Chris

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It could do. It's also worth checking the ballast resistor.

Both these items run hot in service, which brings about degradation.

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I have tested the coil off the car with a multi meter and its showing 1.7 ohms ? When put back on the car it tests at 1.3 ? Does anybody know what it should read ? Is the change in the reading normal ? Or is this a sign that the coil is duff ?

Thanking everybody in advance

Chris

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Chris, sorry I don't know do you have another coil to check against?

BTW John mentioned possible fuel varnishing in the carbs. You could try Redex in the tank, which is good at cleaning such gunk out of the fuel system.

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Could it be the fuel enrichment device (choke )is stuck on? There is only a small spring to return it on the carb and pushing the metal arm down in the cockpit doesn't always mean its off at the engine end.

 

Just a thought. 

 

Buddsy

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Similar problem on mine which is a carb turbo. Turned out to be the 'pick up' in the distributor along with the connecting cable which runs back into the voltage increaser box (AB14)

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