bronco II jerking/misfiring when warm

[projectAtoB]

i just bought a 86 broncoII with the 2.9. when the truck is driven for around 10 min or more it starts to jerk violently and loose power. it will stay at idle most of the time but takes no gas at all. If i let the truck cool down it will run for another 10 minutes great with no problems. I had a similar prob like this with my mustang and it was the coil. i put a coil on the truck that i knew was good and it seemed to help at first. meaning it went longer without messing up but then just started doing it again. I read through the fourms and found people with similar problems and it was the TFI so i replaced that today and it didnt fix it. any help would be appreciated. thanks Jesse

 

[nismotunedgtr]

Fuel pump.

 

[projectAtoB]

just checked the fuel pressure. ignition on engine off 40 psi.

when the problem started 30 psi

haynes manual says 2-10 psi drop is normal with egine running.

 

[IMenriched]

i just bought a 86 broncoII with the 2.9. when the truck is driven for around 10 min or more it starts to jerk violently and loose power. it will stay at idle most of the time but takes no gas at all. If i let the truck cool down it will run for another 10 minutes great with no problems. I had a similar prob like this with my mustang and it was the coil. i put a coil on the truck that i knew was good and it seemed to help at first. meaning it went longer without messing up but then just started doing it again. I read through the fourms and found people with similar problems and it was the TFI so i replaced that today and it didnt fix it. any help would be appreciated. thanks Jesse

Have you pulled codes??
doesn't appear that fuel delivery is the issue, from the other replys...but that being said...when was the last time you changed the fuel filter???

Same goes with plugs and wires, cap rotor, when was the last time it was tuned up?

how about the O2 sensor?

 

[projectAtoB]

im gonna attempt to pull the codes today with a meter, but ive never done that before so it might be interesting. it is just a cheap bronco i just got it, but i changed out the plugs. the wires look semi new but that is just looks. i havent touched the cap and rotor. im pretty sure its a electrical or spark issue but i was willing to try anything so i checked the fuel pressure. there is what seems to be a solenoid beside the starter solenoid that buzzes when i turn the truck off. I have no idea what it is. it has vacume lines coming in the bottom and an electrical connection at the top. Any ideas what it is? i dont know maybee thats my problem?

 

[IMenriched]

im gonna attempt to pull the codes today with a meter, but ive never done that before so it might be interesting. it is just a cheap bronco i just got it, but i changed out the plugs. the wires look semi new but that is just looks. i havent touched the cap and rotor. im pretty sure its a electrical or spark issue but i was willing to try anything so i checked the fuel pressure. there is what seems to be a solenoid beside the starter solenoid that buzzes when i turn the truck off. I have no idea what it is. it has vacume lines coming in the bottom and an electrical connection at the top. Any ideas what it is? i dont know maybee thats my problem?

that is...the map sensor....or iv'e been told anyway.
not completely sure weather the "buzzing" is normal.

post what your codes are telling you...best to go from there.

 

[JSTJ704]

I would pull the codes play guessing games can cost alot. I learned that the hardway I replaced almost every sensor alot 250 bucks or more here it was a pickup coil in the distrubator. Sounds like O2 sensor but you never know pull the codes it help alot.Mine would start missing when warm and shut off and wait for it cools down start up great and run great but when it

 

[projectAtoB]

i tried to run the codes yesterday, but it didnt show anything. Not even the pass code i double checked the way i had it wired up and i am positive it was right by the haynes manual. only thing is the haynes manual asked for a 15 or 20 amp loop and the tester i was using only had 10 or 50. i tried it on both and didnt get anything. i had a digital meter and i thought it would work just display numbers instead of sweeps. and when i hooked the neg and pos. posts it cut some electronics on without the key being on, which it didnt do with the analog meter????? this is my first time doing this can anyone help me out what i am doing wrong?

 

[BlackBII]

Check Here for pulling codes
http://www.therangerstation.com/tech_library/OBD_I.html

 

[projectAtoB]

preciate that i didnt know you could do it with a test light i will try that. haha its pretty much dummy proof (or me proof)

 

[projectAtoB]

i never could get the codes to see what my problem was but i went on a long search and found that the o2 sensor plug was melted. cut the wires spliced in a spare of the other bronco i had truck runs great. puttin some 31s and fender trimin today now.