Weird Idling issue!

Novanutcase · Apr 29, 2009

This just started happening about a week or so ago:

When I pulled up to a stoplight I noticed that my idle was hovering around 1100 rpm and not dropping to the usual 700 rpm. I figured the IAC must be getting dirty so I pulled it, cleaned it and reinstalled it. Started the car and it idled perfectly at 700 rpm. I started it up in the morning and, after it warmed up, same deal 700 rpm at idle. A few miles after that it started to hang at 1100 rpm again. I was at a stoplight so I shut the car off and started it again. 700 rpm. Weird but whatever. I drove a couple miles and, again, idle is hanging at 1100 rpm. Shut the car off again and restart and, again, right back to 700 rpm but if I drive it a couple miles it hangs at 1100 rpm.

Anyone have this problem? I thought it was the IAC but since it isn't consistent I don't think that's what it is. It's almost as if the computer resets to the correct idle when I shut if off and restart it.

Any suggestions as to what this may be?

I'm gonna check and see if maybe it's a vacuum leak but, same deal, if it was it would do it all the time right?

John

Willy Mo · Apr 29, 2009

hmmm, maybe tps? may need to be adjusted. pcv valve stuck open? but i am just shootin in the dark. i never had this problem.

2002 BLK GT · Apr 29, 2009

Clean you maf sensor its connected on your cai get an electronic cleaner from autozone...

Novanutcase · Apr 29, 2009

Thanks Guys!

I went ahead and started with the easiest fix which is disconnecting the battery for a half hour, reconnecting it and letting the car idle for a half an hour so that the computer can recalibrate for idle. I guess I'll find out if it worked on my way to work tommorrow.

If it doesn't work then I'll try cleaning the MAF.

John

00redgt · Apr 29, 2009

clean ur iac also

2002 BLK GT · Apr 29, 2009

You're welcome.... Let me know how it goes.. Lol^ he checked that already.

treblruh · Apr 29, 2009

i just posted in the v6 forum about the exact same thing, tell me if ya find a solution. ive cleaned MAF and the iac with no avail...it started from no where and i cant figure it out.

Thanks
-Dylan

2002 BLK GT · Apr 29, 2009

Then its the TPS...
What is the TPS?

Sitting on top of your throttle body there is a sensor that relays to the computer the exact opening position of the throttle butterfly. In other words, how far do you have your foot into the accelerator pedal. In technical terms the TPS is a low-voltage potentiometer. Based on the position of the throttle and other factors given to it, the computer will decide how rich the fuel mixture will be at any given open throttle point.

Why mess with the TPS?

Well, based on the information given above it is easy to understand how important this sensor is to your Mustang's performance. It is important that the computer gives the correct air and fuel mixture at the right time. If your TPS is off (or bad), the information (voltage) that the computer gets will be inaccurate. The tuning procedures in this article are very simple and the potential for the TPS to be off is significant, so why not tune your car the right way and get the most out of it.

Details:

Tuning the TPS

When you tune up your Mustang (wires, plugs, timing, etc.), the checking/adjustment (if needed) of the TPS should always be included. You will need a Phillips screwdriver, a pin, and a voltmeter that can read low voltages accurately. Here is the procedure:

1) Loosen the two screws holding on the TPS, (The screws can be very stubborn, so make sure you have a good quality screw driver that fits snug and has a long handle for lots of torque, or you might strip the heads) just enough to able to swivel the TPS with force.
2) Pierce the "GREEN" wire with the pin and hook the positive (+) lead from the voltmeter to it.
3) Ground the negative (-) lead from the voltmeter. Use a good ground, like the engine or other grounded metal source.
4) Turn your ignition key to the run position, but do not start the vehicle
5) Rotate the TPS until you achieve .98 to .99 Volts (For stock or slightly modified engines).
6) Tighten the screws on the TPS and recheck.

Troubleshooting

If the maximum or minimum voltage you can obtain is close to the above recommended voltage setting (.98-.99), but the TPS just won't turn enough to get it right, you will have to modify the TPS. If you get a very low voltage reading, make sure you have an accurate voltmeter and your connections are solid, if so, you need to replace your TPS. If you have no voltage, you have a bad connection or a bad voltmeter. Rarely, if never, will a TPS be in such bad shape, especially if your car still runs good.

Trick Tuners · Apr 29, 2009

Novanutcase said:
I thought it was the IAC but since it isn't consistent I don't think that's what it is.

It sure sounds like a bad iac. See if you can borrow one for a bit to test it out, or just buy a new one.

Ke^in · Apr 29, 2009

Willy Mo said:
hmmm, maybe tps?

How would you check such a thing? Is there a tps report I could read?

Does it have a cover?

Novanutcase · Apr 29, 2009

Well....that didn't work but I'm gonna give the computer a day or two to recal. If not then I'm gonna replace the IAC and see if that fixes the problem. If not then I'll replace the TPS.

Big Daddy, I thought that procedure is only good for the '99 - '01?

John

2002 BLK GT · Apr 29, 2009

Novanutcase said:
Well....that didn't work but I'm gonna give the computer a day or two to recal. If not then I'm gonna replace the IAC and see if that fixes the problem. If not then I'll replace the TPS.

Big Daddy, I thought that procedure is only good for the '99 - '01?

John

Why you think it won't work for you??

mystang0673 · Apr 30, 2009

im having this same exact problem. i cleaned the maf and checked for vacuum leaks. Let me know how this comes out and what fixes it...

Willy Mo · Apr 30, 2009

Ke^in said:
How would you check such a thing? Is there a tps report I could read?

Does it have a cover?

"Then its the TPS...
What is the TPS?

Sitting on top of your throttle body there is a sensor that relays to the computer the exact opening position of the throttle butterfly. In other words, how far do you have your foot into the accelerator pedal. In technical terms the TPS is a low-voltage potentiometer. Based on the position of the throttle and other factors given to it, the computer will decide how rich the fuel mixture will be at any given open throttle point.

Why mess with the TPS?

Well, based on the information given above it is easy to understand how important this sensor is to your Mustang's performance. It is important that the computer gives the correct air and fuel mixture at the right time. If your TPS is off (or bad), the information (voltage) that the computer gets will be inaccurate. The tuning procedures in this article are very simple and the potential for the TPS to be off is significant, so why not tune your car the right way and get the most out of it.

Details:

Tuning the TPS

When you tune up your Mustang (wires, plugs, timing, etc.), the checking/adjustment (if needed) of the TPS should always be included. You will need a Phillips screwdriver, a pin, and a voltmeter that can read low voltages accurately. Here is the procedure:

1) Loosen the two screws holding on the TPS, (The screws can be very stubborn, so make sure you have a good quality screw driver that fits snug and has a long handle for lots of torque, or you might strip the heads) just enough to able to swivel the TPS with force.
2) Pierce the "GREEN" wire with the pin and hook the positive (+) lead from the voltmeter to it.
3) Ground the negative (-) lead from the voltmeter. Use a good ground, like the engine or other grounded metal source.
4) Turn your ignition key to the run position, but do not start the vehicle
5) Rotate the TPS until you achieve .98 to .99 Volts (For stock or slightly modified engines).
6) Tighten the screws on the TPS and recheck.

Troubleshooting

If the maximum or minimum voltage you can obtain is close to the above recommended voltage setting (.98-.99), but the TPS just won't turn enough to get it right, you will have to modify the TPS. If you get a very low voltage reading, make sure you have an accurate voltmeter and your connections are solid, if so, you need to replace your TPS. If you have no voltage, you have a bad connection or a bad voltmeter. Rarely, if never, will a TPS be in such bad shape, especially if your car still runs good."

this^^

S IHI II IB IB Y · Apr 30, 2009

Big Daddys Stang said:
Then its the TPS...

+1 :yes

I had the exact same problem with my old 6er a few years ago eventually it may start going WOT anytime the motor isn't under load (which is the extreme that mine went to) and I changed out my TPS which solved the problem. You didn't recently install a new TB did you? I think I jarred mine a bit when I did the TB install which is what caused it to go on the fritz.

Ke^in · Apr 30, 2009

Oh, I was making a TPS report joke from office space. Just ignore me.

Novanutcase · May 1, 2009

OF COURSE......

I swear, these cars are alive and know what we are thinking!

I had a little time this morning to pull the IAC to replace it. Before I pulled it I needed to move into the garage and guess what? She ran perfect!

I drove her for around 20 miles just to make sure that the same problem didn't come back and she idles and decels perfectly! LOL!

I think she saw me with a screwdriver in my hand and she didn't want to be violated so she's behaving!!! LOL!

John

2002 BLK GT · May 2, 2009

LOL at least you resolved everything...

Weird Idling issue!

Novanutcase

Willy Mo

2002 BLK GT

Novanutcase

00redgt

2002 BLK GT

treblruh

2002 BLK GT

Trick Tuners

Ke^in

Novanutcase

2002 BLK GT

mystang0673

Willy Mo

S IHI II IB IB Y

Ke^in

Novanutcase

2002 BLK GT

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