Hi, I have a Ford Bronco II '87 2.9L v6.

Situation: When you go long distances at high speeds the trucks starts dyeing, even after you slow down. What it does is, it'll run and then all of a sudden it decelerates for a few seconds then starts accelerating for a couple of seconds and then decelerates again and accelerates again in a continues cycle... As if I'm pushing the peddle and letting off then pushing the peddle and letting off again. But I'm not. Now if I let it sit for a couple of hours it'll run fine as long as I take it slow and not for a long distance. Also, when it starts to have it's episodes if you stop at a red light or stop sign for more than a couple of seconds it kills itself and you have to restart it. (An hour away from my hometown and doing 45-50 on the interstate hoping it wouldn't just stop was a long trip... lol)

We've changed the fuel filters (even though they weren't clogged or dirty, they were actually only a week old), fuel pump relay, and checked the fuel pressure (stays between 38 and 40) and it's still doing it.

Does anybody have ANY clue as to what might be causing the problem?

Also here is a video of it when it's idling (not sure if it'll help anything but I thought someone might recognize the sound or something.)

YouTube - ‪Ford Bronco II '87 Idling problem‬‏

Thanks in advance!

 

Stick around, holiday weekend and all...some one will be by to help .

 

Also just to clarify on the video it usually dies after it does that, not level out like it did.

Also, Thanks Tim for the encouragement!

 

My '88 BII did that also,,changes all the sensors, 3 relays in right fender under hood, gas filter, TPI, AIC, MAF, TFI module on distributor, clean all the plugs where different harnesses are joined, use di-electric grease there as on the TFI module, etc. improved it some. finally as my last resort,, put in a Reman EEC IV computor(inside right kick panel(O'Riellys or AZ). That solved my problem anyway. check all your grounds also,,battery to body, engine to body, battery to engine(heavy cable off neg battery post)rt side by oil filter, thin braided ground wire by wiper motor to engine and there's a few under dash. get a Chiltons manual. good luck. adios amigo from hot(106) N.Texas staying

 

im betting on the throttle posistioning sensor being bad.. you can take it to autozone and they can test it for you for free...