1994 Ford F-150 XLT 5.0 (302cid) Surging & Bucking

Tiny
CSA1
  • 1994 FORD F-150
  • 210,000 MILES

Truck cranks and runs, When Idling, engine surges. Gets worse when you drive it down the road. Will surge & buck after 40mph. Replaced throttle position switch, coolant sensor, distributor, cap, rotor, plugs & wires. Removed upper intake, cleaned it out. New gaskets, cleaned throttle body including EGR ports, replaced MAP sensor, and replaced fuel filter. Seemed to help for about 15 minutes, then began surging & bucking again. Any suggestions as what to try next?

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Friday, January 6th, 2012 AT 8:36 PM

13 Replies

Tiny
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Have you checked for codes? Fuel pressure correct? Same colde as warmed?

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Friday, January 6th, 2012 AT 8:45 PM
Tiny
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Fuel pressure was 49 psi. Only code that shows is MAP sensor, which I replaced, but code still comes up. & Yes, runs same cold or warm

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Friday, January 6th, 2012 AT 8:50 PM
Tiny
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See diagram Dist look like it? If yes remove TFI have tested VERY prone to cause problems.

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Friday, January 6th, 2012 AT 9:04 PM
Tiny
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What diagram? & What is a TFI?

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Friday, January 6th, 2012 AT 9:14 PM
Tiny
CADIEMAN
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That fuel pressure is whyll the problem is happening?

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Friday, January 6th, 2012 AT 9:17 PM
Tiny
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Fuel pressure good 45 psi

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Friday, January 6th, 2012 AT 9:22 PM
Tiny
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As far as I can tell, fuel pressure to engine is ok, it seems to get plenty of fuel. Shows 39 PSI at the post on the fuel rail. (Miss typed the last one, not 49) As long as you give it gas, it runs great. Has a little miss, but once you let it idle or hold at a steady speed, it surges, & bucks like a mule.

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Friday, January 6th, 2012 AT 9:29 PM
Tiny
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No TFI Module on this distributor

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Friday, January 6th, 2012 AT 9:30 PM
Tiny
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Truck is late 94 so Dist has shutter vane and ICM see diagrams locate and have ICM tested

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Friday, January 6th, 2012 AT 9:38 PM
Tiny
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Had Ignition module tested, passed ( cycled 25 times )
Would the IAC cause this problem? I know it might at idle, but would it cause the problem while driving as well?

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Saturday, January 14th, 2012 AT 6:28 PM
Tiny
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Just tested IAC, it's fine. Went and had codes scanned, here is what it showed:
DTC172 ( o2 sensor fault, lean)
DTC 213 (SPOUT circuit open)
DTC 332 Insufficient EGR flow (had hose off to test EGR vacuum)
DTC 538 Insufficient RPM change during KOER
DTC 632 Overdrive trans cancel switch

we pulled the short bar out of the SPOUT wire harness, checked timing. 10BTC. Put short bar back in & checked timing again, still 10BTC.
Seriously stumped as what to check next.

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Sunday, January 15th, 2012 AT 9:04 PM
Tiny
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I found the problem & got seriously lucky finding it.
Seems the brand new distributor had a bent pickup coil cover that was arcing & shorting out #2 & #6 so they would fire intermittently.
Shoved a screwdriver down the distributor, bent the cover back a tad so it wasn't rubbing. Threw it all together & cranked it. Purrs like a cat now :)
Thanks to all that helped on the one!
Lots of great suggestions & ideas
Also, learned not to buy a distributor made in China!

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Monday, January 16th, 2012 AT 12:22 AM
Tiny
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Great news yes lots of China parts flodding country

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Wednesday, January 18th, 2012 AT 8:56 PM

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