I have a 1995 F150 with the 4.9L I6, 5 speed, XL pkg, 183xxx miles. I replaced the fuel filter, plugs, and wires due to it bucking at any speed intermittenly, and stalling a lot while idling. I also ran some fuel injector cleaner through it. Anyway, it only bucks now intermittently at highway speeds and will still stall sometimes when idling. I also have to rev it up a bit more to keep from stalling out on takeoff. I bought and used a code reader and it came up with the code 556, (fuel pump primary circuit failure). Anyone know how to fix this problem? Any ideas if it's not this?


Secondly, I've noticed my speedometer goes wacky, and I would like to replace the sensor or cable, but I've looked on the transmission and there is neither. I checked the rear differential and found what appears to be a sensor, but no speedo cable running with it. Is that still possibly the speed sensor? The chilton manual didn't show a picture of where it was located, but only states it's on the tranny.

Thanks

 

That is the vehicle speed sensor (vss), and is most likely the cause of your drivability issues as well as your erratic speedo. BTW, your speedo is electronic, and has no cable.

 

Thank you for the tip. I will definitely be checking that out. Now, can you tell me where it is located. The chilton manual doesn't. By chance, is it the sensor located on the tranny with the one bolt that holds it on? Thanks again.

 

It's mounted to the rear axle, near the differential. Yours is part number E9TZ9E731A.

 

Thanks PK for the info. I found the sensor and replaced it. Unfortunately, that didn't solve any of my problems. Since then, I've also replaced the IAC and the throttle position sensor but to no avail. I'll just keep trying to narrow it down. Thanks again.

 

If the VSS didn't fix the problem, then you may have a damaged ring in the rear end. There is a specific ring that has teeth on it the trigger the vss. If either the vss or the ring become damaged, an erratic speedo and bucking will be the result. There are other possible causes for the bucking, but you're quickly running out of possibilities for the speedo problem. I'd recommend having it looked at professionally.

 

If the VSS didn't fix the problem, then you may have a damaged ring in the rear end. There is a specific ring that has teeth on it the trigger the vss. If either the vss or the ring become damaged, an erratic speedo and bucking will be the result. There are other possible causes for the bucking, but you're quickly running out of possibilities for the speedo problem. I'd recommend having it looked at professionally.

 

the code 556, (fuel pump primary circuit failure) see list of codes at www.fordfuelinjection.com getting trouble codes. Remove your battery ground for 10 minutes and get codes again. I wounder if your fuel pressure is ok?

 

Just wanted others to know in case they run into the same problems I had. I took my truck to a mechanic and he found the problem, which was the speedo module in the instrument cluster was bad. He had to get an instrument cluster since the module can't be replaced individually. Thankfully, he got a used one from a salvage yard, and it fixed the problem of the missing/bucking engine and erratic speedo. Just hope this may help someone in the future.

 

Glad you got it fixed! Yeah, a bad PSOM can cause problems like the ones you described. For some reason, I was thinking you had already replaced your speedometer. I should read these posts more thoroughly.

 

Hey bud, thanks for your help though. At least what I replaced kept them from replacing it and costing more to narrow down the problem and that let them look elsewhere right away.