My Car Has Been Idling Kinda ****ty..i Have Replaced The Cap, Rotor, Plugs, Pcv Valve/screen/gromet, Cleaned The Iac...but Did Not Replace The Wires Cuz They Were Pretty New....i Put A Pin In The Green And Black Tps Wires When The Car Was On The On Position...it Read .64 Dc Volts...what Should It Be...i Hear It Should Be .98.... .99...should I Change It..???
Tps Voltage
- Thread starter ja1919
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nmcgrawj
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ram360
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nmcgrawj
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thats right...you might have to slot the TPS slots a little more with a dremel or something if it wont go to .98.
DemonMustang
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rblaine9000
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- Mar 30, 2005
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- Jul 17, 2001
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This was just posted... Try the search.
Here is yesterdays post. http://forums.stangnet.com/showthread.php?t=532298
Here is a How To.
http://www.mustangandfords.com/howto/29458/
Here is yesterdays post. http://forums.stangnet.com/showthread.php?t=532298
Here is a How To.
http://www.mustangandfords.com/howto/29458/
I've read all the recommendations about getting the TPS set as close to .99 as you can without going over, and it makes sense except for one thing: my personal experience (after four 5.0 cars) has been that it is really a matter of trial and error to get a good result that works for your car. I am currently running .54v, after trying to make .98v work forever. But I just kept getting a soft idle that would not snap back in place, and wanted to hunt up and down. I did it all, including using a Ford idle air bypass plate, which allows you to set a static idle screw and TPS setting and then tweak the actual idle speed by air bleeds, but ultimately zeroed in on a compeletely different number that gave me a snappy idle without hunting. It took some doing, but I did get a good steady idle that does not hunt by tweaking it to .54v (although the IAC and bypass plate must be kept clean). But I always had bad result just blindly setting .97-.98v. Frankly, it can't be as simple as just hitting .98, since as I recall the the EECIV F.I. bible by Charles Probst, which should be on every 5.0 owner's shelf, doesn't even mention trying to hit numbers around .98. I think it just says that as long as you are under 1.0v at idle you are OK. And in the nearly 20 years since the 5.0 H.O. motor hit the streets, I don't ever remember seeing an article that actually gave some real-life dyno numbers to prove a difference between .54v and .98v. All they could ever say was that it must be better because the computer knows that it is off-idle more instantaneously. Am I wrong? .54v works better for me on GT40 iron heads; E303; MSD6A; Mac Shorties; BBK H-Pipe; Centerforce Dual Friction; Flowmaster 2-chambers. What's your story on this, I'd be interested to hear?
Personally,I dont think it matters much but do know when moving the throttle to full open it should read around 4.6v.I believe it has something to do with how much the computer meters fuel to the injectors.I actually had to ground pin #46 on the computer itself to get mine to read a steady #
Sam, I dont see a problem with what you are doing. seems to me that the TPS should zero out upon start up/throttle closing anyhow, so long as it is within spec (+/- 25%). if not, codes will fly. 
and with all the idle issues on EFI 302's, i dont think anyone can really fault anything someone does that works. there is obviously no one 'fix' for idle issues (if there were, that guy would be a millionaire. ). so if it works, go for it. the only real difference the setting makes is with the tip-in tabling (not something that would show up on a dyno - the TPS still hits [or should] hit WOT voltage just the same).
for guys with issues or wanting to do all the idle stuff (i feel that if one setting is messed with, it should all be checked. also ancillary stuff like the IAC might as well be cleaned. here is a decent article with pics:
http://www.muscularmustangs.com/iac.html
oh yeah, if someone has some really dippy readings, i would check the wiring itself out. i would check each wire and also goose test each wire.
good luck.
and with all the idle issues on EFI 302's, i dont think anyone can really fault anything someone does that works. there is obviously no one 'fix' for idle issues (if there were, that guy would be a millionaire.
). so if it works, go for it. the only real difference the setting makes is with the tip-in tabling (not something that would show up on a dyno - the TPS still hits [or should] hit WOT voltage just the same). for guys with issues or wanting to do all the idle stuff (i feel that if one setting is messed with, it should all be checked. also ancillary stuff like the IAC might as well be cleaned. here is a decent article with pics:
http://www.muscularmustangs.com/iac.html
oh yeah, if someone has some really dippy readings, i would check the wiring itself out. i would check each wire and also goose test each wire.
good luck.
I'm not sure your problem has to do with the TPS, but if you're gonna reset it, I don't think hot versus cold makes any difference, although I would obviously go for matching operating condition, ie, hot. Have you cleaned out your EGR valve? It actually made a pretty big difference when I did it just before getting a smog check. Smoothed things down noticeably. You have to force the pintle valve open and hose it out with Gummout. I have also occasionally messed up cleaning out the IAC, and had to do it twice. It just happens that sometimes you don't really clean it as good as you thought. Also, you may want to take a good look for a vacuum leak. I found my charcoal canister-to-upper-manifold hose had rotted through up underneath the upper where it plugs in. I only caught it by (surprisingly enough with Flowmasters on) hearing the hiss of an open vacuum line. Another thing to think about is the new cap & rotor -- I've heard of them being bad out of the box. Did your idle problem start after you swapped it? If so, you could easily swap the old one back on for a check.
the EGR system should not be functional at idle - so cleaning it should have no effect on the idle characteristics. if it does, there are EGR, EVR, position sensor issues, etc.
i dont know about others, but i set the idle on a warm motor. i dont care to try and interpolate where the warm idle will fall if i set the idle while the motor was cold (guessing with it at 1200-1300 rpm and hoping it idles at 700 once warm). that seems backwards to me - i would rather set the warm idle and know the cold idle will be higher and probably appropriate.
i dont know about others, but i set the idle on a warm motor. i dont care to try and interpolate where the warm idle will fall if i set the idle while the motor was cold (guessing with it at 1200-1300 rpm and hoping it idles at 700 once warm). that seems backwards to me - i would rather set the warm idle and know the cold idle will be higher and probably appropriate.
Maybe the EGR valve should not be functional at idle BUT, if it has crap in it than maybe it is functional at idle when you don't want it to be, ie, exhaust gas is leaking through the pintle valve when it should not be, diluting the intake charge and causing a poor idle. But all I can say for sure is that it did smooth my idle down when I cleaned it out. Hell, for $.50 worth of gummout and 10 minutes, it's worth a shot. Also, be sure to spend the other $1.50 for a new EGR gasket; if it is cooked on (as it most likely will be) you will break it when you take the valve off. Scrape the old one with a razor and replace. Frankly, I'd do this one first before screwing around with the TPS setting. Try it, you can't get hurt for that price.
Sam, i see your perspective now. i figured that if the valve was coked open, it would spit an position sensor error code (but who knows on that given how they work. ).
yeah, cleaning the EGR sounds like a good idea.
). yeah, cleaning the EGR sounds like a good idea.
