about 4 years ago i turned up the idle on my 90 4.9, using the adjustment screw on the throttle body because it didnt seem to want to idle good. anyway i checked it yesterday and its 1.077, book says .5 - 1, when i adjust it to that it will idle when completely warm but not until then and yes the IAC is new and working. guess im not hurting anything by doing this.

 

If it works at 1.077V and no codes or other driveability issues are present, leave it alone.

 

When I added an aftermarket throttle body to my truck my voltage was out of spec and my scanner showed my TPS at 25% and if I remember right it was supposed to be less than 20%. The only option I had was to drill and oblong the mounting screw holes on the TPS body. Pretty Mickey Mouse if you ask me, but that was the only option. It worked and still seems to be holding position. Killed the warranty on it though!

 

well with the max being 1.0 and me having it set to 1.077 just how far off is that, .07.

 

TPS should be below 0.9v at idle, if the motor won't stay running at that setting then you have a vacuum leak or some other problem.

 

Below 1V is the threshold. Right at 0.9 should be good; most of the mustang stuff I've read say .95-.99, but that doesn't give much room for slop or an incomplete return.

 

Anyone tell me how to measure this? I am getting a TPS code thrown at me on my '90 f250 351w.

Sounds like you all know how to do it!

 

well ill checked all over for a vacuum leak and even replaced the intake manifold gasket. i cant find anything. i really dont know where next to look. thats seems to be how it started out, with a vacuum leak. id get back in my truck and when i started it the ac would blow out the down vent for 15 or 20 seconds. first i replace the upper manifold gasket and that stopped it from doing that but then when driving it would cut out of the vents and blow out the lower vent, id let off the gas and it really didnt seem to help, it would just come back on its own withing a few seconds, since i changed the complete intake manifold set, and throttle body gasket it hasnt done it. when i had the intake off i checked it all over for any cracks and didnt find any, in fact i really couldnt see where it had been leaking. like i said ii have good fuel pressure when cold and hot, im thinking now of maybe something in the distributor might be messed up. there a local pick-a-part that just got a 90 in and im thinking if seeing what they want for the distributor, if cheap enough it might be worth a try, maybe get it and the PCM. i have also read were the MLPS on the tranny can cause all kinds of problems, i checked it and its lined up correctly. tell you im running out of things to think of checking. its to bad because the truck runs great and i really love it. one thing i did do is move my gas mileage back up from 11 - 15 mpg.

 

Sounds like you have a vacum leak in inside the dash, pull off the heater core cover and have a look, maybe pull the heater controls at the same time so you can see it all.

Only other thing that could be related is the vacuum canister on the passenger fender, if it's the metal juice can take it off and inspect the bottom this is where they typically rust out.

 

checked it and its good, also checked under the dash and good vacuum. i should of ever messed with the adjustment screw, or should i say should of had to, but anyway i went to pick-a-part and bought a throttle body off a 90 and cleaned it up and installed it, truck starts and idles great. ill have to wait and see if it starts good when its cold. i still have a slight surging around 45-50 miles an hour.

 

has nay one elongated the holes in the tps sensor so they could set it at 1.0 volts to see if it made a difference. im talking about one that say is at .85 or .90, ive done some reading about getting it closer, say .99 and it seems to have made a difference in starting and cruising. i dont know why ford decided to make the 4.9 non adjustable. from what i understand 1/4 of a volt makes a big difference.

 

How r doin? I have 90 ford f250 5.0 what's the best setting for the tps? I have my setting at.96?

 

Just as previous post mentioned, 1.0 and below is within spec. If it's running fine and the screw hasn't been tampered with, leave it as is. If you have to adjust it, then you have other problems.

 

I have an aftermarket throttle body on it. Well first I have a single bore BC I put an Mustang motor in truck it runs awesome but just want to no where good would be? BC I hear it could mess with MPG,shifting of e40d

 

Cut from oldfuelinjection.com:

"There is a TPS ratchet algorithm which continuously seeks the minimum throttle angle corresponding to a CLOSED THROTTLE position. This alleviates the necessity to set the throttle position sensor at an absolute position and compensates for system changes and differences between vehicles."

•Closed Throttle can be anywhere between 0.6-1.0 volts
•Part Throttle is triggered @ 0.04 volts above Closed Throttle
•Full Throttle is triggered @ 2.71 volts above Closed Throttle

URL: Fuel Injection Technical Library » Throttle Position Sensor (TPS)