This morning I removed the air filter cover from my 1.3 MkII Golf so that I could watch how the choke worked from cold.
The car is not running quite right when I frist start it up but is OK when warm.
1. It startsfirst time and runs A1 for 20 secs or so.
2. It then goes all lumpy when you rev it (or a couple of mins)
3. It then runs pretty much perfectly.
I started it this morning and watched the carb in action. The flap was almost closed when it first started. I let it run for a bit and then noticed a change in the revs after about 20 secs and a different engine noise. The flap was still almost closed.
Could this 'change in engine noise' be a clue as to what is happening (or not happening)please?
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there is a valve fitted on the outer section of the air filter case which tells a flap on the end of the pipe to open.located above exhaust pipe with a tube that should connect to the exhaust manifold.idea is when cold air is coming in the valve operates this flap so as temp increases on exhaust warm/hot air is drawn in to inlet reducing warm up time and giving more efficient burn.taking off the air filter top cover bypasses this operation and will not give an accurate reading of what is going on.your problem may be its overfueling as is often the case but it could also be a HT problem as well ie damp or shorting.I think you would need to try and isolate the problem a bit more?
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I'm not familiar with the Golf carbs, probably more than one type fitted anyway.
Most have an electrically heated coiled spring attached to the choke flap - as the spring heats during cold idling, it tends to straighten and twist the choke flap off. Also attached to the flap is a linkage connected to a fast idle cam (a stepped, snail shaped thingy). From a cold start the choke flap will be closed with the fast idle cam in it's fastest position, as things warm up, the flap should begin to open and reset the idling speed on the cam, you can adjust the fast idle with the small screw that contacts the stepped part of the cam. During warmup the throttle usually has to be operated to allow the choke flap and fast idle to readjust to a new setting. When hot, the fast idle cam is redundant and idle speed is controlled by the main idle speed screw. All of these operations are controlled by tiny lightweight springs and a broken one or slightly sticky component will cause problems. You'll probably find that the heating element is in an adjustable sort of cylinder, loosen three screws and turn to apply choke harder or not so hard, as required. Most of it becomes obvious as you study and fiddle with things, but be prepared for a long and fiddly job, and another go when it doesn't work first time.
There are bound to be other connections to the carb - vac pipes, water pipes etc. that might have an effect on the choke, but checking heater coil and fast idle cam should be your first diagnostic step.
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Thanks to you both.
I haven't replaced the HT leads.
Could these, if faulty, cause such a problem and if so why does it run fine after 5 mins or so. Surely if it is an electrical fault it would miss all the time?
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As Mech1 suggested, damp conditions can cause a misfire when starting from cold. Condensation in a distributor cap, damp around the coil connections etc. A dodgy or high resistance HT lead could lead to the spark earthing in damp conditions before the plug fires. As things warm up and dry out, the spark finds the next place of least resistance - the spark plug.
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Not sure but there could be a spring loaded pull of diaghraph on this carb that opens the choke valve when the vacuum in the inlet manifold is low. ie when you rev the engine.
Look for hoses going from inlet manifold to auto choke. Could be that a rubber diagraph is split when you take the top off the chamber - you can either buy a new one or smear it with clear silicone sealant.
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Visually the choke mechanism looks to be working well.
It is alomost closed when starting from cold and gradually opens over about five minutes or so.
It just runs lumpy every time for about two minutes about twenty seconds after starting up.
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