QuestionMy 74 MGB is running very roughly since cold weather set in here in Belgium.Idles rough right from the start and seems to have little power. Slow to accelerate. where to start on adjustments? same car was fine a mnth ago when weather was warm...
AnswerI'm afraid that's not much information, but let's try, based on the sudden change in behavior.
1) I am assuming that the 1974 still has points. Poor ignition adjustment often shows up when the weather gets cold and *damp*. Make sure your points are clean (filed flat, or new) and the gap adjusted. Even better, convert to electronic! E.g. Pertronix (which I use in my Healey).
If it does get better with this, and you want to avoid damp problems in the future, you should remove the coil and spark plug wires from the distributor cap, clean them all with WD40, and then coat the ends with silicone grease before reinserting them in the cap. That will help keep water out.
2) In the US we have 10% ethanol in most gasoline, and don't have to worry about water. If Belgium does not, you may have water in your tank. Use a can or two of fuel drier in the tank, run the car, and see if it improves. (It's basically methanol.)
3) A sudden release of dirt into the fuel line is quite likely.
i) Change the fuel filter, and at the same time take off the float chamber tops and clean out the float chambers.
ii) Then, with car running without air cleaners, open the throttle wide and completely block the air intake on each carburetor in turn. That should clean anything out of the jets.
ii) If still no good, it's possible you have dirt in the fuel pump or in the fuel line, which is a bigger job. I don't know how to get to the MGB fuel pump.
4) If no improvement, it's possible your coil has gone bad. A mechanic should be able to check the output. A new one is not expensive. Get a 40-kV (sports) one.
Good luck!
PS And, unless the wires you have are new, it pays to spend a little on a new set.
PPS I didn't realize you had done some of this already! One basic thing I forgot. To check both fuel and the fuel line... Disconnect the fuel line at the filter. Take a clean *glass* jar and put the fuel line into it. Turn on the ignition. Fuel should come out at *high* flow rate. (If OK, you do not have a fuel line problem; if not, you do have a problem.) Let the jar settle for 10-15 minutes, and check for water at the bottom of the jar. If there is water, that is one theory answered. Even if there is no water, it is possible you have cleaned something out. Reconnect, with the new filter, and follow the previous instructions. Overall, I suspect water, somewhere! JJ
