'94 F-150 with a 351, suddenly seems to be running on 6 cylinders

Asked by Jul 29, 2015 at 06:06 PM about the 1994 Ford F-150 XLT 4WD Extended Cab LB

Question type: Maintenance & Repair

My '94 F-150 with a 351, suddenly seems to be running on 6 cylinders. Mechanic is
blaming bad fuel pumps, but truck runs exactly the same off either tank, starts right up &
idles so I disagree about fuel pumps. We hooked a gauge to the test valve on the fuel
lines & it reads 35-38 when truck was running. I'm thinking ?injectors? we replaced fuel
filter & cap & rotor. Any ideas for diagnostic or repair?

6 Answers


Are 2 spark plugs wires switched?


Switched, meaning on the wrong plugs. That would do it.


Injectors seldom go bad 2 at a time.

No, unfortunately... It happened after the truck was run on the rear tank tell empty and started to die before quickly switched to the front tank. It was driven 3-5 miles after that, parked and the next time it was started it began showing these issues...


First eliminate a possible spark problem with the plugs, wires etc. If your vehicle fuel injected. If so you could have sucked up some crud from an empty tank and fouled an injector. Also, change the fuel filter.

So I have now replaced the plug wires as well and very little if any improvement. I did run a diagnostic: ER test: Code 172-HEGO shows system always lean Code 213-Spout circuit open EO test: Code 172-HEGO shows system always lean Code 452-Insufficient input from vehicle speed sensor I can't imagine the O2 senor causing all of this... Now where to begin??

Your Answer


Looking for a Used F-150 in your area?

CarGurus has 220,224 nationwide F-150 listings starting at $1,222.


Ford F-150 Experts

  • #1
  • #2
  • #3
View All

Related Models For Sale

Used GMC Sierra 1500
887 Great Deals out of 59,332 listings starting at $1,980
Used Dodge Ram 1500
327 Great Deals out of 9,602 listings starting at $800
Used Toyota Tacoma
428 Great Deals out of 41,122 listings starting at $2,600
Used Ford Mustang
291 Great Deals out of 38,369 listings starting at $1,995
Used Ford F-250
417 listings starting at $3,500
Used Ford Explorer
831 Great Deals out of 64,217 listings starting at $2,000
Used Chevrolet Tahoe
633 Great Deals out of 37,460 listings starting at $795

Used Cars For Sale

2018 Ford F-150 For Sale
41 Great Deals out of 140,712 listings starting at $19,500
2017 Ford F-150 For Sale
177 Great Deals out of 11,369 listings starting at $18,450
2016 Ford F-150 For Sale
198 Great Deals out of 8,185 listings starting at $14,500
2015 Ford F-150 For Sale
334 Great Deals out of 10,371 listings starting at $11,990
2014 Ford F-150 For Sale
538 Great Deals out of 12,889 listings starting at $8,991

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.