1986 bronco ii with a constant miss

Broncoman1532 · Jan 27, 2012

New to the forum and like the site (ton of helpful stuff) ihave an 86 bronco 2 with the 2.9 and it has a constant miss I have done plugs wires cap rotor. A friend said to replace inigtion control module (tfi) would it cause the constant miss. I have checked for spark at every plug. Another friend said a fuel injector. I also have another ? I have a fuel pump from a 90 bronco ii is it okay to replace it with the one in my bronco. My float does not work and wanted to switch it to a plastic float. Thanks for the help

kuivinenj · Jan 31, 2012

sounds like an injector to me i got a b2 for free that way it was skipping a cylinder so the guy told me to get it out of his yard when i got it home i pulled the fuel rail and injectors off, one was full of sand and rust so i replaced it runs smooth now so try that. also if u do take it apart oil the injector o rings it goes back together way easier that way

sjr53 · Feb 7, 2012

The 86 has 2 fuel pumps, a low pressure pump in the tank and a high pressure pump on the frame. The 90 will have just 1 high pressure pump in the tank, or so I have been told.

big red 138 · Feb 10, 2012

do you know which cylinder is missing? if you dont do a power balance test. once you locate the cylinder with that is missing, runn a compression test, cranking and running

power balance test: with engine running, pull one ignition wire at a time. each one pulled should cause an drop in RPM. the one that does NOT lower engine RPM ( or has smallest drop) is the weak cylinder.

Compression testing: once you locate the weak cylinder, run a cranking compression test ( disable the ignition by either removing the ign. wire at the coill)( watch for 4 "puffs") should be somewhere between 125-160psi. (thats industry standard, however all mine were around 170-180) compare it to 1 or 2 other cylnders to make sure theyre all close. if that all checks out, or it is slightly lower, remove the valve core from the compression tester ( so you can watch compression and loss of compression as it goes through the stroke) hook the compression tester up to weak cylinder ( hook the ign. wire back up) and let he motor run. compression while running should be around 60-90psi. but get the readings and shut it off. it IS possible to hydrolock a motor with gas, not easy but why risk it.

good luck man, let us know what works!

shadow88 · Feb 10, 2012

The 90 b2 dose have one fuel pump, in the tank only

joenorthcarolina · Feb 13, 2012

I just bought a 90 BII.
I had the same problem. I pulled the plugs and discovered which injector was bad. #4 was the problem on mine.
Runs like a champ now.
I recommend running some fuel additive to clean that cylinder/piston rings and valves. I bought a large bottle of Lucas for $12 at Autozone. Its enough for 100 gallons of gas.

1986 bronco ii with a constant miss

Broncoman1532

New Member

kuivinenj

New Member

sjr53

New Member

big red 138

New Member

shadow88

Member

joenorthcarolina

Member

Sponsored Ad

Sponsored Ad

Members online

Today's birthdays

Member & Vendor Upgrades

Latest posts

Truck of The Month

Recently Featured

Follow TRS On Instagram

Latest Album Photos

TRS Events

25th Anniversary Sponsors

Check Out The TRS Store

Sponsored Ad

Sponsored Ad

Sponsored Ad

Amazon Deals