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My engine since startup from rebuild has a miss at idle. It is very noticable when standing at the rear by the tail pipe. It will idle along fine for a short period than miss mostly one time, then sometimes a couple misses consecutively. Other than that it runs fine loaded and unloaded.

I have noticed the same thing on some other MV jeeps.
My old 9N ford tractor does the same thing but worse. but I don't want to spend any money on it right now. It probably needs a new carburetor.

On the jeep, I wonder if there might be a leak in the intake somewhere. Maybe around the carburetor possibly. Since it really wasn't giving a performace problem I haven't trouble shot it. In my past occupation I was a trouble shooter and repairer in the industrial instrument/electrical field. It's not like me to let this miss continue without finding out why. So some time soon I am going to have to start the process of elimination. Wish my luck.

It can be as simple as moisture in the gas or as difficult as carbon tracking in the distributor cap. It could be an occasional valve/lifter sticking. It could just be a momentary fouling of a plug. I wouldn't run out and buy a carb kit. The carb delivers the same stuff to all cylinders at the same time. The ignition and the valves decide what to do with it.

I've got one of those old Ford tractors as well.....a 2N.......and fact of the matter is......if it didn't give that occassional "phooop"...."phooop" I'd think there was sumptin wrong with it. Its been doing it since I was big enough to be around the tractor when daddy would start it up. And in the past 50 years I think its been overhauled twice......and its still done it afterwards....both times. My old shade tree uncle always used to say just to be sure and keep a good muffler on it so as not to warp the exhaust valves any further.......but even brand new valves never made any difference so I'm not real sure my uncle was standing under the right tree when he made that call. Anyway.......my four cylinder jeep does the same thing.......fact of the matter is......that's kinda why I bought it.....nostalgia!!! Would kinda sorta be a shame to fix it now and lose that delightful feeling of being all young again. hehehe...

Well since the the engine only has maybe 1500 miles on it I would discount the the valve lifters in the trouble shooting the first go around. Not saying that it isn't the culprit though. Yes one of my first thoughts was that it might be in the distributor cap. I have a spare one to use. So that will probably be the first to try. I just got lazy and didn't want to do anymore work on it. It took me four years to restore it. I just wanted to drive it since it wasn't a major problem.

Its normal

Ken,

I have noted the same thing on more than one Willys Overland L head engine.
I was starting to think it was normal.

I do not think it's normal. Mine did it too, since I've bought it (two months) but after carb adjustment it was a touch too lean, it completely disappeared. It did no difference in driving the Jeep, but I did not like the occassional puffing sound in an othervise healthy, smooth idle. Last week I had another car in my shop with miss at idle, also fixed, different cause, but that car was not a Jeep.

I had the same problem, when the heatriser did not work correct, and the preheating stays on. Sometimes it happens when the jeep stood still for a day of 14. After a good ride, it disapears. With a lean fuelmixture i had also the same symptoms. In our club there are more CJ3A's and MB wich have this problem. The M38A with his F head engine seemes not to have this problems, or am i wrong ?

Erik