I will be replacing my TPS on my 93 F-150 with a 5.0, e4od. Is this a difficult task? What type of things should I watch out for? DO I have to remove my throtle body? Is there certain positions or angles I have to set it at to operate properly? I am only 16 with minimal mechanical skills, and can't afford to bring it to a shop. Also will be replacing the IAC valve. Should I replace the gasget as well? Does a new IAC valve come with a gasget?

thanks in advance,
ryan

 

on my 93 is the TPS adjustible or does it bolt on right out of the box? does the TB assembly have to come off. PLEASE HELP!

Ryan

 

Remove the throttle body and flip it over. The TPS is on the bottom. It is probably adjustable, it is on my 92 w/ 5.0L. Your Hayne's manual should have a testing procedure, if not you can find it with a search thru this site. It involves back probing 2 of the wires and measuring voltage with a volt meter. I don't know the voltage off hand.

The IAC should come with a new gasket. Pretty straight forward there, 2 screws on the TB and a wire harness.

Put a new gasket on there for the throttle body when you re-assemble.

Piece of cake, don't sweat it. If you don't have a Hayne's manual for your truck yet...get one. It'll get you thru a lot of jams like this.

 

Really is a piece of cake as low92 said.

Be careful to set the TPS right, or you'll have all kinds of weird problems that make absolutely no sense.

Per www.fordfuelinjection.com:

The TPS should be adjusted such that the output is 0.90 - 1.05 volts when the throttle plates are fully closed. The voltage should read 4.95 - 5.00 volts when the throttle is turned to WOT (wide open throttle). Take some friendly advice (after all, it's free) and go to the website above. It's one of the most informative sites I've ever seen on the OBD-I and OBD-II systems.

The little set screw on the throttle body is NOT for idle adjustment. That screw is ONLY for a throttle stop to keep the throttle plates from binding in the venturi. If it hasn't been moved, DON'T MOVE IT.

The EEC will control the idle by means of the IAC. That's what the IAC is all about. It bypasses the throttle plates and meters enough air to keep the engine idling at about 872 RPM.

After you get the new TPS and IAC installed, that would be a really good time to check manifold vacuum. Do this with all vacuum lines disconnected and the nipples capped or plugged to make sure you don't have plenum or intake leaks. The only lines that need to be connected during the tesing is the MAP sensor and the Fuel Pressure regulator. Good vacuum is around 19-20 inches. (get the right gauge from your favorite parts house.) If you are at 17 or below, chances are you have a leaking plenum or intake gasket, or perhaps a really bad EGR. EGR's usually squeal very loudly when they're leaking. Still not the end of the world. Removal and replacement of the plenum shouldn't take more than about an hour each way. Keep a shop vac handy to pick up all the little bits of gasket and remove all the debris that collects on the intake. Where you'll spend most of the time is cleaning the TB and plenum. You'll see when you get it off, that there will be significant carbon deposits from the EGR on the back sides of the throttle plates and around the ports for the IAC and EGR. Clean this off. The carbon will cause surging idle. But, BE GENTLE and don't scratch the inside of the TB, especially where the throttle plates seal. If you have a spare toothbrush, they work nicely. Get a can of Seafoam, and soak it for a while, and most of the gunk will come right off. If you get to the point of pulling the plenum, that would be a good time to spend an additional $8 and put a set of O-rings on the injectors.

Once you've tested vacuum with the lines removed, hook them back up one at a time to verify the vacuum at each step. You could hook 'em all back up, but then, if you have poor vacuum, which one's leaking? These 5.0's are very intolerant of extra air coming from leaks. They'll miss, buck, snort, wheeze, oscillate and do things you didn't think an internal combustion engine could do. But, keep 'em right, and they last a LONG time. I started with the brake booster, then the EGR, then the Cruise, then the TAB/TAD supply lines. Found two leaks doing this, and did it EVER make a huge difference.

You may also want to check the EGR. The nature of that beast is that it's going to leak some. Use an unlit propane torch to test for leaks. Get the gas going in with the leak, the truck will idle smoother and a little faster. You'll know if you find a leak, real quick.

When all is said and done with the air/fuel system repairs, don't forget to check the timing. Disconnect the spout wire, and set it for 10 BTDC, per Ford specs. You might cheat a little and advance it slightly for a little more economy and zip, but you might just cause it to ping very badly too.

While you're doing all this testing, expect to generate some codes. Start the KOEO, and when it starts flashing the codes at you (after the first marker flash), pull the jumper out of the diagnostic link. It'll reset the ECM, and any stored codes.

Hope this was helpful.

 

thanks for the info! i think i'll start by replacing the IAC first to see if that fixes my problem. The TPS sounds a little out of my league.