BroncoII4x4.com

i have a 1986 b2 with a 2.9 i just got it back form the shop where there replace the igntion mod, and a few other odds and ends. it ran good for a few days but now i got a miss from 2 grand to 3 grand when i run down the highway and a little stumble when i take off. i would take it back to the shop but i had planned on swappin in one of my back up race motors from my racecar this winter. so i dont want to spend much money into the 2.9.
is there something i need to be checking or can be changed really "cheap"

thanks ya'll

spark plugs and plug wires if not already done

i would recheck your timing, and also chek your MAPP or MAF sensor too it migh be loose o coroded connection which can cause a miss and can vary on the rpm influences

whats a mapp? im new to the whole electronics deal

ok the MAPP OR MAF sensor depending on which the truck has is located right next to the breather box where your air filter is located on fuel injected motors or right against the air horn where the hose goes into the throttle body for the fuel injection system, it has an electrical plug going into it and will be one type or the other, i do believe on the 2.9 it is the MAF (type which simply means Mass Air Flow) it is involved in determining the air fuel mixture the injectors will distribute through the intake manifold into your cylinders..... i knwo if it comes unplugged or has a loose connection it can cause motors to run with a miss, run rich, flood out, or starve for fuel, it can create all of the above problems, i had an explorer that the clip on the plug broke off of and it ran bad untill i used a electrical zip tie to fasten the plug so it didnt vibrate loose when driving after that it ran like a new truck ......

TFI Module Resistance Test: (9)



The TFI module may be removed, and tested for resistance between terminals to determine complete failure. Often stock TFI modules only partially fail when engine temperatures get warm, and the vehicle runs rough then dies. The vehicle then restarts, and runs for 20 seconds then dies again. This is a defect, which affected ALL TFI modules before 1995, although some do not seem to be very problematic (this is often causes codes 14 and 18).

ok thanks i really want to try to check that. wheres it at and how do i change it

http://www.broncoii.org/techpages/eeciv/index.htm
...... this link gives a diagnosis page that will point you int the right direction, and it gives the info on what everything should read....... hope it helps.

i posted the link if it doesnt stay there for you then send me an email at paulbelden1@sbcglobal.net and i will send you the link in a email, the page gives a lot of good info for testing the electrical components on a bronco II but mainly for fords, even gives the meanings of all codes .....

alot of people call the TFI sensor an ECM but it is located on the distributor, and it runs the ignition system on the broncos, i cant say its the problem but it wont hurt to check it and it give the information on how...

TFI Module Resistance Test: (9)



The TFI module may be removed, and tested for resistance between terminals to determine complete failure. Often stock TFI modules only partially fail when engine temperatures get warm, and the vehicle runs rough then dies. The vehicle then restarts, and runs for 20 seconds then dies again. This is a defect, which affected ALL TFI modules before 1995, although some do not seem to be very problematic (this is often causes codes 14 and 18).



D1 to H1 12.8K

D1 to H2 17.4K

D1 to H3 1000

D1 to H4 11.5K

D1 to H5 4.2K

D1 to H6 0.0K

D2 to H1 1.2K

D2 to H2 5.8K

D2 to H3 12.6K

D2 to H4 100

D2 to H5 15.8K

D2 to H6 11.6K

D3 to H1 100

D3 to H2 4.7K

D3 to H3 13.7K

D3 to H4 1200

D3 to H5 16.9K

D3 to H6 12.7K

D1 to D2 11.5K

D1 to D3 12.6K

D2 to D3 1100

D1 to BASE 0.0K

D2 to BASE 12K

D3 to BASE 13.1K


sorry it wont let me psot the location of which pin is which, but there is a pi9c on the site listed that shows which is which, but you should know i printed the entire page ..... or manual that was listed there and it was about 15 pages and covered different sensor locations and what they should read.... along with other info thatr i found would be usefull....

hope it helps