I have a 1991 Ford F-150 XLT Lariat with the 5.0. Trucks been running good and everything until yesterday I was two tracking and hit a bump and my fan took a chunk out of my upper radiator hose and coolant was spraying everywhere. Got it fixed and it was running good. It sat over night and started up great this morning until I noticed it wasn’t letting me get high into RPMs before shifting up and then it started to almost instantly shift through all the gears until it hit 4th. And now when I give it more than just light throttle it wants to bog down. I was thinking it could be the throttle position sensor since it’s also high idling (which has done this before in the past and TPS fixed it). I was thinking maybe coolant could’ve thrown it off or made it malfunction. Also one more thing to note is that the speedo and tack don’t work (tired to replace the sensor and the little plastic gear that go into my transfer case but didn’t help, even put a drill on the cable and made sure it still spun which it did) I came to the conclusion that the gear in the transfer case just got worn out). But it has ran fine without it and shifts fine without it until today. I think I’n the past when the TPS went out it didn’t effect shifting bc the speedo was still hooked up but now that it’s not, the TPS went out and could be messing with the shifting.

Any insight would be greatly Appreciated as I don’t have a backup car atm and am dailying my truck!

 

Welcome to the site!

Would'a figured our more experienced guys would have chimed in by now, but I'll give 'er a spin.

Tach issue - no idea here, mine didn't have one so never had the opportunity to work with it.

Speedo issue - would be interesting to know whether the speed registered with the drill spinning the cable - hopefully you have a reversible variable speed to be able to check both directions of cable rotation. If not, suggest either a broken cable or a problem with the speedo. If so, then would agree it's something in the tranny case.

Since you mentioned everything got sprayed, would suggest to pop the distributor cap to make sure things are dry inside. Always had a similar issue when I would Gunk the engine and hose off - would start and run fine until it warmed up, then misfire. Usually just left the cap off for a couple hours, maybe with a fan blowing on the innerds. Also may consider inspecting any electrical connectors or places where water/coolant could get in for being dry.

As for the high idling, may wish to inspect the idle-air control (IAC) solenoid. This generation had challenges with the innerds getting fouled, causing erratic idle with high speeds and/or loping/surging. Carb cleaner works good to clean out so the piston moves freely across its entire range.

 

Hey thank you for the feed back! Tore it apart this morning and removed throttle body to replace sensor on the bottom, cleaned everything through a new gasket on and put back together and it fixed the shift problem and idle problem. Tmr imma go through with some electronic cleaner and dielectric grease and clean up all the connections just to be safe.