IDLE?TPS?SURGEING

You have to get that TPS in the .94 to .99 range.

that tps will screw you if you dont have it set in the guild lines

90lxnotch said:

do i mess with the throttle stop

Click to expand...

Not if you don't have to.

Just elongate the holes in the TPS to get it set to where you want it. Also, if the car doesn't surge with the IAC disconnected, I suggest either cleaning or replacing it.

Good luck.

unplug the IAB, set your idle around 600 with the screw. Then plug the IAB back in, if it still surges set your TPS to ~4.5@WOT, you should be good then unless a sensor or two needs to be replaced. You shouldn't have to adjust your idle with the screw(and IAB plugged in), but many people want a higher idle to keep the vacuum up with larger cams.

Metoo

I have the same problem.

Wont help but at least you're not the only one

Sure you have no vaccum leaks or gasket failures anywhere (considering that's the number one smooth idle killer)?

check agian and again for any VACUM LEAKS!!! i had about 5 million of em' on mine, and didnt even know it!!!! thought that the carb cleaner thing would for sure tell if one was present, but it didnt... finally i just capped of any accesories that were off of the vacum tree!!! upon hiding the wires on my passenger side engine bay, i seen that everyone of the egr vacum lines where all cracked to h***. o well you live an learn i guess... just check for another one, cause i almost guarntee thats what it is!!!

I keep my TPS set close where the factory had it.. I think its at about .87v now. I used to set it up in the high .90s I've heard if yer gonna do this not to go higher than .95 or so, otherwise the ECM thinks the throttle is open a tad and the IAC compensates and makes it idle high... my car would never idle rightthat way, so I put it back to where it is now.

Myself, I think the TPS mod is a do not do. I mean, what voltage does the EEC need to see in order to go into PE mode [power enrichment mode was what is was called in the T Types ECM when you went WOT, and "PE" voltage was only like 2.6v I think] because as long as your getting that... which they do from the factory, untouched, then you're good.

What i'd be more worried about.... Have a buddy floor it inside the car and observe the throttle plate inside the T body, and if it is infact going all the way open. I remember reading in MMFF that that was one thing that was wrong with some of the 5.0s is that they dont get actual full throttle..

This is what I saved a while back... I think I found this on the Corral....

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The "idle screw" that everyone is referring to is actually a throttle stop. It was never intended to be used to adjust the idle because the computer is designed to control the idle to a preset level programmed into the ecu - 672 rpm. It does this by monitoring rpm and telling the IAB solenoid to let more or less air bypass the throttle plate to stabilize the speed. While some folks have luck setting the idle speed higher, just as many only create a machine that constantly surges and hunts for a constant idle speed as the computer "fights" with your attempts to increase the idle speed by turning the throttle stop screw. You should also reset your tps level down to .95V or lower - having it up around 1.0V (.99V) can also cause the idle speed to do funky things. If the idle problem appeared NOT as a result of other changes you made I'd try this:
1) remove throttle body and iab solenoid and clean them thoroughly; reinstall
2) Set the throttle stop back to its proper location - back it completely off (unscrew it); place a .003 feeler gauge between the screw tip and the throttle arm; tighten it til it just touches the feeler gauge; then remove the feeler blade and tighten it 1/4 turn more.
3) Set your tps to .95V with the ignition on/engine off but warm
4) Disconnect the battery with the headlights turned on - leave it disconnected with the headlights on for a minute or 2.
5) Reconnect the battery and crank it up. During the next few hours (cummulatively) of driving the computer should 'relearn' and begin controlling the idle with more stability.
Good luck!! Chasing down funky idle issues is one of the toughest things the efi crowd deals with.
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Worked for my car for the most part. I surge a bit when the car is warming up, but its fan wash from the clutch fan air hitting my cone I think... and after it warms up to temp, still its pretty steady on my car

I agree. Thoroughly cleaning the TB & IAB should solve your idleing problem. A lot of crud builds up in this area and can wreak havoc on your idle.
My stang idles steady at 700 with SC/H/I.

I agree. Thoroughly cleaning the TB & IAB should solve your idleing problem. A lot of crud builds up in this area and can wreak havoc on your idle.
My stang idles steady at 700 with SC/H/I.