I recently purchased a 1989 f-250 351 zf-5 work truck. From the day I bought it it idled rough, almost like it was missing. I used this as a bargaining point thinking it might be an easy fix. The fuel pump was staying on for various periods of time after shut down so by what I have read on the site I assumed it was the computer. I replaced it today and it fixed the fuel pump issue but, now it still has the rough idle and it stalls out. It will idle for anywhere from 5 to 30 min and then it acts like it runs out of fuel. It will restart after a few good cranks but the problem repeats itself. If anybody could give me some advice on what to look for next it would be greatly appreciated. Thank You all in advance!!

 

anybody? I really need some help on this one. Have to drive this truck to UT next week and, right now scared to.

 

I think that I would begin by checking for code's, and by doing a complete tune up if needed. beyond that you could check the air idle bypass (IAB) control. The site below will give you a lot of how to info...good luck

p.s. the computer is normally the very last thing on the truck to go bad

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