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1986 F150 keeps shuting off and backfiring


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Ford Mule
New User

Sep 10, 2010, 2:42 PM

Post #1 of 4 (3189 views)
post icon 1986 F150 keeps shuting off and backfiring Sign In

Okay heres the deal, I have a 1986 F150 with a 4.9 liter (300 cid) inline six. I know its old but heres the problem and I'm not much on vehicles built atfer 1972. The truck was running fine then all of a sudden one day coming home from work it just shut off. If wait a couple of minutes it will start and run but if try to start right after it shuts off will get a really loud (sounds like a canon) backfire. After startup will go about 2-3 miles and shut off again. It has TFI-IV ignition which I know nothing about and an electronic feedback 1bbl carb that was just rebuilt. It also idles rough at times but not always. Last backfire destroyed the muffler, it split the seam of the muffler. Not to sure where to begin, any ideas or help would be greatly appreciated. Truck has 178,547 miles on it.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Sep 10, 2010, 7:59 PM

Post #2 of 4 (3176 views)
Re: 1986 F150 keeps shuting off and backfiring Sign In

It's old with some miles and I can relate to thatCrazy

TMK these engines are good but had problems with head bolts that are one time use turn to torque which caused some strange problems. If still original the timing chain needs to be checked. Same tricks as any - many used nylon cam gear that doesn't age well and can jump. Check for how much "lash" it has by turning crank bolt at TDC and watching distributor's rotor. Note that much more than 5 degrees it means trouble. If OE and a keeper just do that stuff.

Late carbs by any maker were a problem. Stuff on the vintage is fixable and durable so decide on invest some or give up based on overall condition. They rusted badly here fast so not many around now. What do you want to do?

T



Ford Mule
New User

Sep 13, 2010, 7:11 PM

Post #3 of 4 (3142 views)
Re: 1986 F150 keeps shuting off and backfiring Sign In


In Reply To
It's old with some miles and I can relate to thatCrazy

TMK these engines are good but had problems with head bolts that are one time use turn to torque which caused some strange problems. If still original the timing chain needs to be checked. Same tricks as any - many used nylon cam gear that doesn't age well and can jump. Check for how much "lash" it has by turning crank bolt at TDC and watching distributor's rotor. Note that much more than 5 degrees it means trouble. If OE and a keeper just do that stuff.

Late carbs by any maker were a problem. Stuff on the vintage is fixable and durable so decide on invest some or give up based on overall condition. They rusted badly here fast so not many around now. What do you want to do?

T



Ford Mule
New User

Sep 13, 2010, 7:18 PM

Post #4 of 4 (3141 views)
Re: 1986 F150 keeps shuting off and backfiring Sign In

Thanks Tom I'll check it out.






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