Setting Base Idle Questions... is something wrong?

Tps needs to be unplugged as well. Also make sure the spout is disconnected.

the stop screw for the throttle body? It would most certainly affect the tps which is why it needs to be unplugged.

you are supposed to plug it back in after you set your idle.

See the "Surging Idle Checklist” for help with all your idle/stall problems. You can guess at the problem and throw parts at it, or you can use the checklist to help you find the problem quickly and inexpensively. It’s free and doesn’t cost anything: at last count there were more than 103,000 visits and still climbing

The quick and easy way to dump the codes is in there too, and all you need to do it is a paper clip! The first two posts contain all the fixes & updates. At last count there were 24 possible causes and fixes for surging idle/stall problems. I continue to update it as more people post fixes or ask questions.

See http://www.stangnet.com/mustang-forums/698148-help-me-create-surging-idle-checklist.html#post6855020 for the best way to set the mechanical base idle and cleaning procedure for the IAC/IAB.

JasinC19 said:

Thanks, that helped. Now when I adjust the TPS, turning it all the way counterclockwise only gets me to 1.00v, and when I try to tighten it, it inevitably creeps up to 1.02v or more.

If I loosen the stop screw, would it affect the TPS adjustment range?

Thanks again

Click to expand...

aftermarket tps sensors (and sometimes the oem depending on your setup) often do not have enough adjustment, and the slotted hole may have to be enlarged. dont be too worried about keeping a specific voltage, as long as its in range its fine.

TPS troubleshooting

Setting the TPS: you'll need a good Digital Voltmeter (DVM) to do the job. Set the TPS voltage at .5- 1.1 range. Because of the variables involved with the tolerances of both computer and DVM, I would shoot for somewhere between .6 and 1.0 volts. Unless you have a Fluke or other high grade DVM, the second digit past the decimal point on cheap DVM’s is probably fantasy. Since the computer zeros out the TPS voltage every time it powers up, playing with the settings isn't an effective aid to performance or drivability. The main purpose of checking the TPS is to make sure it isn't way out of range and causing problems.


Wire colors & functions:
Orange/white = 5 volt VREF from the computer
Dark Green/lt green = TPS output to computer
Black/white = Signal ground from computer

TPS troubleshooting steps:
1.) Use the Orange/white & Black white wires to verify the TPS has the correct 5 volts source from the computer.
2.) Use the Dark Green/lt green & Black/white wires to set the TPS base voltage. Try this... All you need is less than 1.0 volt at idle and more than 4.25 at Wide Open Throttle (WOT). You'll need a voltmeter with a 1 or 3 volt low scale to do the job.

The Orange/White wire is the VREF 5 volts from the computer. You use the Dark Green/Lt green wire (TPS signal) and the Black/White wire (TPS ground) to set the TPS. Use a pair of safety pins to probe the TPS connector from the rear of the connector. You may find it a little difficult to make a good connection, but keep trying. Put the safety pins in the Dark Green/Lt green wire and Black/White wire. Make sure the ignition switch is in the Run position but the engine isn't running. Set the voltmeter on the 2 volt range if it doesn’t auto range.

Here’s a TPS tip I got from NoGo50

When you installed the sensor make sure you place it on the peg right and then tighten it down properly. Loosen the back screw a tiny bit so the sensor can pivot and loosen the front screw enough so you can move it just a little in very small increments. I wouldn’t try to adjust it using marks.

(copied from MustangMax, Glendale AZ)

A.) Always adjust the TPS and Idle with the engine at operating temp. Dive it around for a bit if you can and get it nice and warm.

B.) When you probe the leads of the TPS, do not use an engine ground, put the ground probe into the lead of the TPS. You should be connecting both meter probes to the TPS and not one to the TPS and the other to ground.

C.) Always reset the computer whenever you adjust the TPS or clean/change any sensors. I just pull the battery lead for 10 minutes.

D.) The key is to adjust the TPS voltage and reset the computer whenever the idle screw is changed.

The TPS is a variable resistor, must like the volume control knob on a cheap radio. We have all heard them crackle and pop when the volume is adjusted. The TPS sensor has the same problem: wear on the resistor element makes places that create electrical noise. This electrical noise confuses the computer, because it expects to see a smooth increase or decrease as the throttle is opened or closed.

TPS testing: most of the time a failed TPS will set code 23 or 63, but not always. Use either an analog meter or a DVM with an analog bar graph and connect the leads as instructed above. Turn the ignition switch to the Run position, but do not start the engine. Note the voltage with the throttle closed. Slowly open the throttle and watch the voltage increase smoothly, slowly close the throttle and watch the voltage decrease smoothly. If the voltage jumps around and isn’t smooth, the TPS has some worn places in the resistor element. When the throttle is closed, make sure that the voltage is the same as what it was when you started. If it varies more than 10%, the TPS is suspect of being worn in the idle range of its travel.

TPS will not go below 1 volt
Engine mounted sensor circuit: Check the resistance between the black/white wire on the TPS and battery ground. It should be less than 1.5 ohms. Higher resistance than 1.5 ohms indicates a problem with the 10 pin connector, computer or the splice inside the main harness where the wire from the 10 pin connectors joins the rest of the black/white wire.



See the graphic for the location of the 10 pin connectors:
Diagram courtesy of Tmoss & Stang&2birds



See the graphic for the 10 pin connector circuit layout.


Unplug the white 10 pin connector to do some resistance testing. It is good time to clean the connector pins and examine the connector for corrosion, broken wire or other damage. See http://oldfuelinjection.com/?p=85 for help in this department.

If the resistance on the TPS Black/White wire and pin 1 of the white engine fuel injector harness 10 pin connector, is more than 1.0 ohm, you have bad connection or broken wiring. Repeat the test using the pin 1 of the white body side 10 pin connector and battery ground. You should have less that 1.5 ohm. More than that is a damaged signal ground inside the computer or bad connections or wiring.