1993 5.0HO swap in a 1990 F-150 surging problem

Zackattack78

New Member
Feb 2, 2019
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New Bern, NC
Hey guys this is my first post so here I go, I recently put a 1993 5.0HO in a 1990 F-150 and have every truck part and sensor on the motor including the truck ecu, it runs beautifully going down the road at 60mph...the issue is the the motor is surging terribly at idle or slowing down at a stop light, I have looked for every possible problem head to toe looking for vacuum leaks to replacing every sensor like the map sensor and nothing fixes it does anyone have a clue how to fix this or had the similar problem?? By the way this is my first ford motor I have messed with lol so I’m a newbie
 
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Zackattack78

New Member
Feb 2, 2019
4
0
1
23
New Bern, NC
What was the firing order of the 5.0 you pulled out?
The same as the one you installed?
Nope the 5.0 I pulled out the truck is the original motor it has a firing order “15426378” and now the motor in it has the firing order “13726548” I switch the wiring the way it’s suppose to be and runs good just surges badly.
 

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