Hesitation

[Leejr57]

86 Bronco II 2.9,auto 4 wd, truck stumbles after driving for a few miles. Replaced fuel pump,(both), egr valve,fuel pressure regulator, (old one was pumping gas through the vacuum tube!), and ignition module. What's left?

 

[Psychopete]

Sounds like something electrical might be going out of whack when it goes into closed loop. The '86 does not have a functioning check engine light, it might be throwing a code. Looks for ECC-IV Dianostics in the technical library. It's pretty simple with an analog volt meter, or a test light would work too. Keep in mind, with the engine off, it will display KOEO (hard faults), then store memory codes.

It's possible that some CM codes might related to previous problems depending on how recently the work was done.

You also might try temporarily unhooking the oxygen sensor (tape the connection so it cannot melt to the manifold or collector) to see if it resolves. It's not used until the engine is warm, but could be something else. Pulling codes first would probably be a better starting point though.

Pete