Trying to get a 88 f-150 running again after a 3 year sit. It was donated to my son by his grandfather. Can't turn down something that's free. Had to replace the in tank and the high pressure fuel pumps and filter because they were all gunked up. New plugs, flushed cooling system, cleaned plenum and throttle body. Did have a vacume leak but that's fixed. It's running now and does OK until the engine get's warmed up good then for some reason the engine idle RPM increases to a higher than normal level. There's no tach but my guess it's around 1500 rpm. Sort of tough on the trans at a stoplight. Idle is normal when cold. When it does this you can open the hood and push the throttle conection above the throttle body forceing it against the idle stop and the engine slows down to a normal rpm. But once you step on the gas pedal the rpm goes up again. Can't see where it's sticking and when the rpm goes up the check engine light goes on. Checked the codes and im getting a 53/63. Throttle position sensor high and low position out of limits. Question is could the TPS be resetting the idle rpm or is there something else going on. There are no vacume leaks. Also need to replace a freeze plug that's rusted and leaking. Can a new one be knocked in with a socket. Thank's for any help. SHM

 

Maybe the engine coolant sensor

 

If you can physically push the throttle closed then you have a problem with the cable or the throttle shaft. There is no computer control over the throttle position, the only thing that operates it is your foot or the cruise control. It is possible that the TPS is stiff and stopping the return.

 

I think i'll go ahead and replace the TPS to start and see where that goes since it was coded. Thanks

 

I would also lube the throttle cable to make sure it is not sticking either. You can posibly mount an additional throttle return spring to help close the throttle plates.

 

i am having the exact opposite problem with my 95 f-150, got totally cold soaked for 3 days at -40 temperatures, when i got it restarted it seemed to be running fine. after it warms up the throttle idles way low, almost stalling, and the pedal response is weak at best. turning the truck off seems to reset the problems for a few minutes but then BAM pedal goes to mush, idle drops. I am pulling my hair out and thinking about just blowing it up and starting over. any help would be appreciated

 

If it can be, I'd yank the cruise control cable off the throttle linkage and see if that's what's pulling the throttle open too. Could be a leaky valve in the cruise system pulling on the diaphragm in the cruise vacuum motor. Your TPS codes are probably coming from the throttle being held partially open when you start it. Make sure the throttle is going all the way back to the stop screw. DO NOT ADJUST the stop screw. It's there ONLY to keep the throttle plates from binding in the throttle body. As others suggested, I'd also make sure the throttle cable wasn't sticking.

 

i sprayed down the throttle linkage with miracle oil, let it sit for a few hours, checked all lines making sure they were hooked up, check all electrical connectors for same. i got busy with honey-do list and wasn't able to get back to the truck until the next day. started it up, drove it around and no problem. i tried it again the next day and all is well. i don't understand it and i am not going to question it. thanks for all the help and great ideas.

 

these trucks, like most vehicles, do not like to sit for an extended time.

after sitting for three years you are lucky it runs at all.

besides getting it going i would take a look at brake lines, front suspension and rear shackles for rust.

 

Definitely the brake lines. Been there, done that with the VW, several times. It's a toy, so it sits extended periods. This is a killer for the rubber lines on the front and rear. I wouldn't be surprised at a rusted/stuck wheel cylinder or caliper, either. Best bet, go ahead and get new rear wheel cylinders (about as cheap as the rebuild kit which won't help if the bore is pitted), rubber hoses for front and back, and kits for the calipers. Three years is a LONG time for one to sit with brake fluid in 'em. Brake fluid has a lot of alcohol in it, which is a magnet for water. Combine that with the oil in the fluid, and you'll get acidic sludge that will eat up cast iron (wheel cylinders and calipers) very quickly. Even if you don't have any leaks right now, you probably will have soon.

Not being able to GO is one thing. Not being able to WHOA is a whole other story.