TPS voltage ?
 

We got the ZEX hooked up - we checked the TPS voltage while we had the DVM out, what should we be seeing for TPS voltage? I believe we were getting .87 at idle.

I would say between .97-.99 would be ideal . Mine is at .975 and runs great .

Keep it closer to 0.93-0.95 instead of 0.998 or whatever others recommend. Your voltmeter (unless you spent a LOT of money on it) will not be that accurate, anyways. The risk of a surging idle increases quickly the closer you get to 1 Volt. FWIW, you may find it advantageous to notch out the TPS so you can adjust its position. Remember to double check afterwards with all accessories turned on!

Mike: yeah, .975 seems to work for most ppl, including myself. I just bumped it back to 0.96 the other day b/c of surging. Ended up my ground cable wasn't worth $h!t. :(

There is a black plastic piece on top of the TPS - do I remove that piece to adjust the voltage as you guys mentioned? If not, please let me know how to actually adjust the TPS voltage.

Thanx

NO! Do NOT remove the little black plastic thingy on top of it. That's the seal for the "guts" of the sensor, so that's a big negative. :) You merely adjust the idle stop screw with a (short) flat blade screwdriver until the TPS voltage is satisfactory. Don't worry about the position of the throttle blade, the computer will take care of idle speed fine. You shouldn't need to rout out the TPS to adjust it like I did unless you're doing something dumb like I am (long story!).

If you temporarily bump the voltage past 1.0V, you will immediately notice a surge in power from the engine. This is the crossover point so the computer "knows" when to get the message, "okay, time to drive!" Just an FYI and something interesting if you're curious.

This article explains it. Here's my non-relevant rant on the article: Some of it is a bit of an overkill, like letting the computer KAM die for 20+ minutes :rolleyes: and having to let the car "learn" idle speed under full electrical load and whatnot. I say that's just being impatient. Fuel injection is not so unpredictable. Just set it, forget it, and drive. Unless you actually get something to reprogram the EEC computer, you're fighting hard-wired programming that wants to idle at 650-750 RPM with a TPS voltage of <0.95V @ closed throttle position.

He might be referring to the black plastic snap on cover that can be found on some TPS's, and yes, it can be removed with no problem. You will see the two screws to do your adjustment underneath this cover.

for whats it worth, dont fret too much over your TPS setting, as its pretty much a waste of time.

OH! THAT cover! DOH! Sorry, my bad! :o I completely forgot some ppl had those, none of my own 'Stangs have ever had 'em on there! :p

In this case, yeah, Mach's right. Lift it up and you should see the two screws. However, it still remains the same way to adjust the voltage as before: with the idle stop screw. Like he also said, it's sometimes a waste of time. If you've got nothing better to do, go for it. You *may* notice a better off-idle response (especially in MAF cars), but ususally it's driver perception. I'm pretty damn sensitive to things like this, so yeah, I'll sit there and bugger with it for as long as it takes for me to be happy. :)

Capri - Im not sure I think adjusting TPS with the idle stop screw is such a good idea. After all, by opening the throttle body butterfly by adjusting the stop screw, you could mechanically increase your idle speed, (or decrease it) when all you have to do to set the TPS is loosen the screws on top, and twist it, all the while keeping your "idle" throttle body butterfly at a normal position for idle speeds.

why cause more headaches when there no good reason to do it that way in the first place?

I adjust like MACH 1 does by loosening the screws and moving the TPS alittle.

Capri 306, you adjust with the idle adjument screw, well in since isn't that just raising or lowering the idle. I get what your saying about adjusting it that way,, because your are basically moving the throttle asd the sensor reads it. But are you saying by adjusting it with the idle screw the EEC will bring the idle back down to compensate??

I think he is saying that, and I disagree , as the EEC cant not compensate for a mechanically larger air passage into the engine. Maybe a small amount with the Idle air bypass valve?

Usaully when I first install a motor I set the idle to the desired RPM with the screw then adjust the TPS and never had any probelms like that. And that is the only time I mess with the idle screw.

I agree with you MACH 1, but I would like to understand how the way he described works.

Well, theres a lot of bad information out there, just keep that in mind when deciding what works and what doesnt.

FYI the offical "Ford" way is to bolt it on and go as long as it is under 1 volt at idle (actually 1.1 on eec 4's) and above 4.6 WOT the eec handles it. and the way to adjust your idle is to unplug your iac motor crank the car adjust your idle hardstop screw to idle where you want it to idle at kill the car. Then disconnect your battery for 15 minutes, plug the iac back in hook the battery back up and start and idle the car until it idles steady again at that point it has "re-learned" the new idle and will idle where ever you want it to. If you go through the whole ordeal of setting your idle correctly make sure your tps is still under 1.1 also before you disconnect the battery because if it isn't then when you hook everything back up the computer will neveer go through the proper idle learn procedure. Also it is amazing how smooth you can make even an E-303 idle by doing it this way. It will still sound like you have a cam but 99% of the hunting and surging will be gone.

Thanx for all the replies on this post guys! The problem I'm having is our car will idle fine then after several minutes of running the idle will creep up to around 2K. When the car idles at 2K if we kill the engine and restart it's back to normal idle - then it'll creep back up again.

Would this be the TPS, or EGR, or something else?

That doesnt work for everybody, I had surging idle issues and tried EVERYtHING, including what you describe with poor results.