Running worse when warm

MC001

New Member
Hi folks

Have a 1972 2000 sc. When the car is warm it starts to run 'lumpy'. Is this likely to be a carburettor thing or something else ? It's hunting I guess you'd say.

I think the idle needs adjusting, but thought I'd check collective wisdom. Why only when warm?

Cheers all
 
What’s the ambient temperature when this happens? What sort of condition are the carbs in? Also, where’s the temp gauge when this happens?
 
So many possibilities...coil getting hot, condenser, cracks in the dizzy cap,failing plug leads, air leaks in the inlet manifold. Check for plug lead failure -run it in the dark looking for visible sparks, or , one lead at a time off the car, meter across the ends, twirl the wire like a skipping rope, looking for the meter reading to change. When its hot, spray something lightly flammable (thin oil?) on all the joints on the carb and the inlet, looking for a change in engine note. Inspect and clean the inside of the dizzy cap and the rotor for cracks or carbon dust tracks. The coil can get warm, but should not get so hot you cant hold it . Any sign of oil in the coolant,indicating a head gasket problem - coolant looks like milk coffee,or has visible oil drops in it? Is the choke fully home (off) when its lumpy? is the air cleaner OK, not clogged? Do you know the revs at the time? Does it drive ok generally, and when the idle is lumpy?
 
Check the tappet clearances. If they are too tight, with a warm engine they close up even more, and the idle will be lumpy. If the tappets are too quiet, it is an indication that they are too tight.
 
Part of guidelines for posting for help with problems - what has been changed recently, worked on etc? is the problem a sudden change, or has it slowly crept in? I once sold a P3 and got a phone call a few weeks later about it running rough. What have you changed? Nothing. Nothing at all. When pressed further, they admitted they had swapped battery polarity to neg earth so they could fit a modern radio....Did you also swap the coil connections, as they are polarity sensitive? silence.
 
Hunting is normally caused by a manifold leak. To check run a bead of oil around the joints while th eengine is hunting. It'll stop when you get to the leak or you may see the oil beind sucked in at that point. When cold the rich mixture will hide the leak. Don't use too much oil as the exhaust is right underneath...
 
Check that the fuel line is routed under the the top heater hose, not above the top of it. Heat from the hose can cause fuel vapor problems.
 
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