I've got a '94 7.3L turbo and it seems to run great but idles way way to high. When I first start it in the morning it sits at almost 2000rpm and after driving a little it drops to 1000 and stays there. The truck never really warms up no matter how long I drive it and I'll be doing a thermostat on it as soon as I get some coolant but I don't think this is the cause. I tried adjusting the throttle cable stop but it's all the way out and is still idling very high. I was thinking about playing with the tps but have no idea if this will help. Any ideas or help on how to adjust the idle is appreciated.

 

The fast idle solenoid can be set by turning the brass plunger in or out as required to attain 800 rpm. Do this on a warm engine by removing the wire and installing a temporary 12V jumper. The fuel lever will require to be pushed back to allow the plunger to set. The main (hot) idle speed (650 +/- 50) is adjustable by the screw accessed from the front left side (facing) the IP, The screw us right beside the F/A solenoid. DO NOT change the screw on the back of the fuel lever. Try this and report back....

CAUTION:
The specified/required thermostat does not contain an internal bypass, since the bypass is located in the cylinder block. Whenever the thermostat is replaced, it is mandatory that only Motorcraft E5TZ-8575-C or Navistar 1807974C94 thermostat be installed.
CAUTION:
Do not attempt to repair any thermostat. It should be replaced if it is not operating properly.
Check the new thermostat before installing it for correct opening temperature. Before suspending in boiling water, with a flashlight check where the rubber and the flat metal flange meet for bad seal. Tstat should start to opening barely at 180-192f, fully open 200-212f, allow to cool and check for rubber seal again.
Removal: Disconnect batteries, drain 4+ gals A/F, remove: as required, fan belt, alternator set aside, alt bracket, remove filter support from fuel filter then e/block. Disconnect upper rad hose at rad, remove tstat bolts and housing. Clean both faces, depression and holes in block, ensure check ball in goosekneck is clean, free and rattles "do not remove".
Installation is reverse proceedure, I do not use sealant on gaskets and faces. REMEMBER the tstat pellet(copper end) goes into the block. I do use a "very small amount" of sealant on the edge of the tstat face when installing into the recess, now go for coffee, allow sealant to setup, this has saved me from tstat slippage when the gasket and goosekneck are installed. Replace all items in reverse order......
Manifold bolt torque......... 20ftlbs

 

That is an awesome post, thank you very much. I got the thermostat directly from ford and have already checked it with a flashlight. I'll dunk it it boiling water next to make sure. I have some time now so I think I'm gonna go try to adjust the idle, I'll let you know how it goes.

 

Okay, the truck idles normally now and sounds so much better/quieter. I had to turn the plunger down almost half and inch. I think someone had turned it all the way out for some strange reason. The thermostat opens properly and will be installed in the next day or so. I think I can say the truck is now in good shape instead of having tons of problems when I first got it.

 

I think I found out why the plunger was turned out all the way. I just took the truck for a test drive and the overdrive off light is blinking and the tranny shifts really hard. I'm guessing there is some sensor that doesn't like the throttle being lowered but I'm not sure what it is. Could throttle position have something to do with it? Thanks in advance, this forum is awesome.

 

if your od light is blinking and you have hard shifts, either your tach is not working properly, or your vehicle speed sensor is not working properly.
either of these will put your trans in "limp mode"

 

That doesn't make a lot of sense since the tach and speedo both work normally and the only thing I changed is the throttle position. Tach and speedo operation haven't changed at all.

 

Okay, I adjusted the tps and the trans got out of limp home mode and I can drive normally again. Mostly normally anyway, it shifts a bit high but it's definitely doable. I'll get a new tps does anyone know how to adjust the new one once I put it on? The diesel guy at our local ford dealership knew next to nothing about "those old pieces of junk" so I return to here. Any help is appreciated.

 

well, what do you expect. that truck is almost 12 years old!!
that means it was made when he was in what?? 4th grade??
i mean really!! what were you thinking.



i can't help you with the tps adjustment, i drive an "older piece of junk", and it ain't even got a tps on it.

 

Search posts by PLC7.3,
He has given the proper proceedure for setting the TPS here before.

I did not pay much attention, I only drive manuals.

 

To bad we can't hook you up to an excellent artical on "the other" web site. TPS set up simplified- Key on engine off- voltmeter- negative to ground (on battery) paper clip along side wire into connector on tps gy/w -center wire-positve lead of voltmeter. At ilde position voltage should be 1.05-1.1 V, then at Wide open throttle position should read between 3.8 but not more than 4.3 V. Thsi made a huge differance in my shifts, once set up properly. If you don't get these voltages, you need a new TPS. Get er done.

 

Well, the old TPS wouldn't get those voltages so I got a new one, the only problem is that the new one wouldn't get the voltages either. It would either be in at idle or WOT but not both. I set it right about at 4.0V at WOT and it seems to drive and shift very nicely. It ended up being about .90V at idle but doesn't seem to have any problems. I probably could have just used the old one but oh well.