MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - sputter

I have a sputter I cant seem to work out. Under normal driving at about 3,000 rpm it will sputter (or miss) in first gear. It does not do it as much in any other gear, mostly first. If I accelerate slowly it does not do it. I have played with timing and mixture, avdvancing and retarding, and leaner and richer. Any suggestions?
David

Check the dashpots in the carbs for smooth operation. May be sticky piston or a bad damper valve that is allowing the dashpot to raise too fast or flutter.
John H

David,
I am running a weber 32/36 downdraft.
David

With examining my spark plugs, three were greyish white, one was black. Could this be plug wires? That would cause my sputter correct?
John

Sorry I put your name at top...meant to be addressing you.
David

Greyish-white indicates a bit weak to me, and one black indicates bad ignition to that cylinder (both of which could cause misfiring under various conditions) or possibly bad rings/valve seals. Ignition problems could be cap, lead or plug related, the latter two relatively easy to swap to another cylinder. You could also prove it to the cap if you rotate the distributor 90 degress and move the leads one position back. Or by buying a new cap, but I hate spending money when I don't have to.
Paul Hunt 2

Thanks Paul, I am hoping to find an ignition fault. I have swapped caps and rotor, points are fresh and I have double checked the gap. I also thought the color indicated a weak mixture. When I set it a bit richer the sputter increased. As for rings, the engine was rebuilt about a year ago and never gave any trouble. It doesnt smoke or burn oil. The cylinder head and valves were checked, at that time I was told the head and valves were good. It can sit for a week then still does not smoke when started so I think the valve seals are good. It all but has to be the plug wires. They were not refreshed with the engine. (dumb on me) I will give this a try and see what happens. Thanks Again for helping me narrow this down. I always over look the obvious.
David

David,
I had what sounds like the same issue a few years ago. I did all the things you have done to no avail. I finally took the MG to an MG professional. I told him what all I had changed. The one thing I had not change was the condenser. He replaced the condenser and I have had no problems for several years.

Dave
Dave kalp

The kind of black that you are seeing will make a difference in the diagnosis. Sooty black whould indicate rich mixture or miss firing, Oily black would be just that, oil from a ring or valve guide problem.
John H

John,
I am seeing a sooty black. The plug was able to be cleaned to be reused. I am going to get my hands on an extra set of plug wires today and hope for the best.

David

I overcomplicated the problem. I am knocking on wood as a speak, but plug wires seem to have cured me.

Thanks for all the input!
David

David: now that you have solved your problem,if you ever get a chance to hook one to your B you would really enjoy an ociliscope as it will quickly show exactly where in your ignition system your "CARBURATOR" problem is! Ric
RIC LLOYD

This thread was discussed between 09/04/2008 and 12/04/2008

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now