TPS Issue?!

RangerJoe · May 6, 2011

Got in my car the other day and started it up, shot right to about 2200rpms. Cut it off, started again, same. I can drive it around for a little while and it seems to go away, but sometimes it returns. I can disconnect my IAC and it will fall back to my base idle, about 800rpms.

I pulled KOEO codes and got a code 23, TPS. I thought my problem was going to be with the IAC, so I took it apart and cleaned it. I went back through the Idle Setting List but still came out with the same result...seems to have gotten worse though, about 3000rpms this time.

I have cleaned the TPS connections and reset TPS, its at .977 with throttle closed and 3.99 fully open. I also have the correct voltage and grounds coming in, no problems there. So I am to the point of thinking I need to replace the TPS. Anyone have any other ideas before I drop $45?

Thanks!

jrichker · May 6, 2011

Check out the stickys at the top of the 5.0 Tech forum. You will find this gem: http://www.stangnet.com/mustang-forums/825424-adjusting-your-tps-0-98v-not-necessary.html

Look in it for some direction and answers.

RangerJoe · May 6, 2011

I have already read through that and a dozen other post; I will read over them again in case I missed something. Just to update, I bought a new TPS today, still same problem.

Something is telling the IAC to open up and provide more air....I am missing something here...someone please shed some light on this.

Thanks!

RangerJoe · May 6, 2011

Update....Installed new TPS, reset it to .968 volts. Unplugged battery cable and let sit for 30 minutes this time. While waiting, I took the IAC apart and cleaned it, again. I also used my multimeter to test the two prongs on the IAC. I found that they have continuouty. I took the selonoid part of the IAC off of the valved portion. The plunger inside the selonoid did not appear to be stuck...I could push it in using a small punch. The small plunger being pushed in or out did not effect continuouty. I can also shake this part back and forth and hear it rattle inside a little. Started car up and it idled fine for about 15 or 20 seconds, then the rpms shot up again. I'm not getting an error code this time, i don't know if it should be present right away, or if I would have to let it run for several minutes for the code to be present.

I don't know if anything I have described is even relevant. I'm not sure how the IAC actually operates inside, so I thought the above might be useful. I hate throwing money at something in order to fix it. I would rather figure out what is wrong with it. Does this seem like the IAC is bad?

Thanks.

jrichker · May 6, 2011

Re-check the TPS signal ground & check the 10 pin connectors. Use non-flammable brake parts cleaner to clean the pins and sockets. Use a jeweler's screwdriver to spread the male pins open to make better contact after you have cleaned them.

See the graphic for the location of the 10 pin connectors:

See the graphic for the 10 pin connector circuit layout. Pin 1 on the white connector is the signal ground for the TPS and other engine mounted sensors

If the ground for the TPS goes bad, the TPS output voltage increases and the idle speed goes up.

Troubleshooting signal ground problems:

Note that all resistance tests must be done with power off. Measuring resistance
with a circuit powered on will give false readings and possibly damage the meter. That means disconnecting either the battery positive or negative cable since there is always some current draw due to the computer and radio circuits.

1.) MAP circuit: Check the resistance between the black/white wire on the MAP/BARO sensor and then the black/white wire on the EGR and the same wire on the TPS. It should be less than 1 ohms. Higher resistance than 1 ohms indicates a problem with the 10 pin connector or the splice inside the main harness where the wire from the 10 pin connectors joins the rest of the black/white wire. Next check the resistance between the black/white wire and the negative battery cable. It should be less than 2.0 ohms.

2.) Engine mounted sensor circuit: Check the resistance between the black/white wire on the TPS and battery ground. It should be less than 2.0 ohms. Higher resistance than 2.0 ohms indicates a problem with the 10 pin connector or the splice inside the main harness where the wire from the 10 pin connectors joins the rest of the black/white wire.

Repeat the process for the ACT and ECT sensors. Your results should have the same specifications.

Mustang5L5 · May 7, 2011

Do you still have the code 23? If so, the computer is not seeing the proper voltage, so even if the tps checks out, you might have a loose connection somewhere and the voltage the computer sees is not what is at the tps.

Clean the 10-pin connectors. You can verify by pulling the computer off, turning the key to on, and checking for voltage on the pin the tps signal returns to and ground (or pin 46)

Tps signal pin is pin 47

RangerJoe · May 7, 2011

FIXED!!!

Well, I cleaned the salt and pepper shakers, still no change. Reference the above post, my Code 23 went away after installing the new TPS. I woke up this morning and went out to crank it. It started, then died. I tried this several times with same results. I could give it gas and it would stay going, but letting off resulted in it dying.

I knew this was classic signs of a bad IAC, so a trip to the parts store netted me a new one. No more problems, and my car has not idled this well since I bought it. No more hanging idle when coming to a stop and it does not seem to surge as badly. I'm still not sure why I tripped Code 23, unless it was just a coincidental thing...perhaps one can trigger the other? Who knows...anyways, thanks for the help and maybe this will help someone in the future.

To sum it up:

IDLES UP & WON"T COME DOWN UNLESS YOU UNPLUG IAC, = Bad IAC

jrichker · May 7, 2011

If you had closely read the latest update to the the "Surging Idle Checklist , you would have found this helpful tip:

Recommended procedure for cleaning the IAC/IAB:
Conventional cleaning methods like throttle body cleaner aren’t very effective. The best method is a soak type cleaner used for carburetors. If you are into fixing motorcycles, jet skis, snowmobiles or anything else with a small carburetor, you probably have used the one gallon soak cleaners like Gunk or Berryman. One of the two should be available at your local auto parts store for $22-$29. Take the solenoid off the body and set it aside: the carb cleaner will damages some types of plastic parts. Soak the metal body in the carb cleaner overnight. There is a basket to set the parts in while they are soaking. When you finish soaking overnight, twist the stem of the IAB/IAC that sticks out while the blocker valve is seated. This removes any leftover deposits from the blocker valve seat. Rinse the part off with water and blow it dry with compressed air. The IAC/IAB should seal up nicely now. Once it has dried, try blowing through the bottom hole and it should block the air flow. Reassemble and reinstall to check it out.

Gunk Dip type carb & parts soaker:

The $22-$29 is much cheaper than the cost of a new IAC...

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