Timing Will Not Set Accurately

I just bought a '85 Bronco with the inline six. It seemed to run ok but would buck and run really rough when lugging in 2nd or 3rd. It had been sitting for an unknow number of months so I started with an engine tune up. When I went to check the timing the mark would only appear once every few seconds and even then not always in the same place. I pulled off the distributor cap and checked everything inside. It all looks good, however if I try to turn the rotor by hand it will turn up to 1/8 to 1/4 of an inch and when it turns it rises up about a 1/4 inch. I know the centrifical advance/vacume distrubutors had internal movement but I'm not sure if this one should. It is the TFI-IV ignition set up. Should there be any play in the rotor at all?? Any and all advice would be greatly appreciated.
Thanks in advance.
Jim
 

Mike 97 SS

Banned
Location
U.S.A.
I know that if there is excessive slack in the timing chain, the mark will jump all over the place. Just a thought. How many miles on it?? Mike
 

jakegypsum

Senior Member
Location
new jersey
I would make sure that there is no vacuum leak at all. A primary leak that can happen is at the bottom of the vacuum hose going to the brake booster. I have had FOUR F-150's have this problem. The brake booster vacuum hose lay's on the manifold and eventually wears a hole in the bottom of the hose thus causing a vacuum leak. This leak can verywell go unnoticed. This leak can cause the engine to lag and sometimes buck. It is a simple fix but you need to know to look for the leak in order to make the repair. It can be overlooked very easily. Jake.
 
Vacuum Hoses

As I mentioned above there is evidence of "work having been done" in the engine compartment. There are many electical connectors that don't connect to anything and the distributor setup is shown as '87 and later in the haynes manual I have. I will check all the hoses tomorrow and keep my fingers crossed that's all it is.
Thanks for the info.

Jim
 
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