I have 79 mgb. The car only runs at a slow idle. Once above idle it runs rough and dies. Does this car have a control box?


Asked by Feb 19, 2012 at 09:59 PM about the MG MGB Roadster

Question type: Maintenance & Repair

I have 79 mgb. The car only runs at a slow idle. Once above idle it runs rough and dies. Does this car have a control box? Also the tach swings wildly when the problem is happening Mark

3 Answers


These cars are fairly simple. Was the car running fine then just developed this problem? You either have a fuel/carb issue or poor electrics. Is the original carb on the car. No control box. Check the connections to the coil - make sure there are no loose wires and that connections are solid. Pull the distributor cap and check all is ok in there - is the rotor arm ok, points gap correct, etc. If the electrics look solid you may have a fuel flow issue. Could be anything from a failing fuel pump to a poorly adjusted carb. Did you get the car like this or was it running fine and developed this issue. Also, do you have a manual choke or is it the original automatic choke? I have an 80 and swapped to a manual choke. Check out www.victoriabritish.com - I buy my parts there and have been very happy with them. Good luck, Bev.


Check the ignition system: plugs, leads, points, condensor, rotor arm, distributor cap and coil. As far as I know there's no control box, the tach bounce is indicative of a severe ignition issue. Potentially there is something seriously wrong with the advance system on the distributor (broken or stuck spring).


Thank you both for the replies. My description of the situation was incomplete. At this point the car will run for ten to twenty seconds and stop. After about five seconds I hear a loud click and it will start and run for ten seconds and die as if it was shut off by the key. It must be electrical. I just can't locate the source of the noise. Any ideas? This weekend I will go though the primary side, put in an old coil and give it a shot. Thanks again, Mark

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