'89 F250 cold idle problem

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Aug 17, 2010 | 02:21 PM

whisler

Thread Starter

Laughing Gas

Joined: Aug 2010

Posts: 983

Likes: 49

From: Northern Kentucky

'89 F250 cold idle problem

Hi folks, new guy here! Well, actually an old guy but new to forum. I recently got a good deal on an '89 F250, 5.0L, 5 spd, 4X4. The previous owner couldn't get it running and sold cheap. i don't know what his problem was but a fresh battery and fresh gas got it started. I do have a problem that I need help with, though. When the engine starts, it momentarily idles near 1200 RPMs, then drops off to stall. Restart and it will usuallly do about the same thing but not quite stall, then high idle, then back to 300-400 RPM and back and forth gradually improving until it gets warmed up. Once warm, it idles smooth as silk. I thought the ECT was bad and replaced it but there is only slight improvement. What else would you suggest? Remember I am an old guy; carbs I understand, but EFI not so much.

Aug 17, 2010 | 04:24 PM

Lazy K

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Joined: Jan 2005

Posts: 8,402

Likes: 10

Ford Fuel Injection Idle Air Bypass (IAB) Have a read here about the IAC valve, may need cleaned. Also instructions in the list on the right of that page for checking for any stored trouble codes (self test). Might be worth doing that.