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MG MGB Technical - Engine Surges

I have a 78 MGB that has the manual choke installed, while idleing the engine will drop about 2k rpm then bounce back up, Ive put in new spark plugs, spark plug wires, checked the air filter (looks good) looked and replaced any hose's that might be loose or cracked, checked the oil in the carb (good), What I need to check is the timing but have yet to run out and get a timing light. Any advice would be great!


T Wood

Check the throttle shafts for wear. If they are excessivly worn, you will have a vacuum leak that will cause the symptoms you are seeing. to test, grab the end of the shaft and see if there is any movement up and down or back and forth. Good luck - Dave
David DuBois

Thanks for the info David, One of the things Ive noticed is that it seems to get worse when the engine is hot however its not over heating and my oil pressure is good. Needless to say Im rather stumped, only thing left to check is the timing but I have never seen timing so off that it makes a engine surge like this, Then again its been over 15 years since I owned a MG.

T Wood

Oh another thing the engine runs like a champ, it only does this at idle, while going down the road its quite peppy.
T Wood

Is there a leak in the brake servo? Try
plugging the line from manifold to the servo and
see if this makes a difference.
Ronald

Thanks Ronald, I replaced that hose the day before you posted that but that would have solved one of the headaches! LOL, I went down to the local parts store and got some carb cleaner and starting spraying around the hose's and gaskets...low and behold the gasket where the carb meets up with the intake is either trashed or needs to be tightened down, think Im just gonna replace the thing and not worry about it. Thanks again everyone for the in-put, doing the timeing and rockers this weekend as well as the gasket, if that doesnt stop the popping and surging the next thing will be to slap a webber on her, Never trusted those Z-S Carbs too much but thats my own lack of understanding em.
T Wood

This thread was discussed between 03/04/2004 and 08/04/2004

MG MGB Technical index

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