Idle too high after TB install...

[Bad89stang]

Just installed a 65mm TB/EGR on my car (because it was basically free) and now my idle is a little too high. It idles at about 900 now instead of 750 where it used to be. It also pauses at 1200 (with the clutch in) after being on the gas and then idles down to 900. I have tried a different TPS sensor and had the same result. I also switched out another IAC, but it didn't work either. Do I need to reset the computer or reset the TPS voltage?

BTW, I realize that I will not gain any performance from the TB until I switch out the intake and heads. I just wanted to put it on for the hell of it. I actually did match the intake with the new TB for what it is worth. I may be crazy, but I think there is a tiny improvement in power. Maybe it is the new shiny parts creating less wind resistance.

[Big Bopper]

I would reset your computer first and then set your T.P.S.

[Bad89stang]

I reset the computer, but the TPS will have to kiss my ***% until tommorrow. Heck, it's only 3:15... What's the problem? I am not a Mustang addict or anything. Thanks for the help though.

[Big Bopper]

"The first step is admitting you have a problem"LOL



I HAVE A PROBLEM TOO!

[Bad89stang]

I can quit anytime...
Just one more modification.
I don't have a problem...
I just have to wipe down the engine.
I don't think about mustangs that much...
Maybe I should re-locate the battery next weekend
No really, I do have a life...

I need counseling...
But with that money, I could get heads and maybe some longtubes.

[PKRWUD]

You must reset the ECM after making adjustments to, or replacing, either the TPS and/or the IAC solenoid. Otherwise, the ECM still thinks it's the old one. It must be reset, and allowed to relearn.

Take care,
-Chris

[Coupe5oh]

You should feel a small gain, if you matched it, plus the tb advertisement says the 65 makes more power on a stock intake....

did you fix it?

[Bad89stang]

Haven't fixed it yet, because I have to get a digital voltmeter. How much do they cost? I have a normal kind with the needle.

I really think that it made a difference. Remember, the ads don't tell you what motor they experienced gains on. Most of the time it has heads, cam, etc... Rarely is it a stock motor. Since I got the wider tires and Draglites my car has been hooking up great on the street. However, now it goes sideways when I punch it at 3000(moving at 20mph) in 1st. Before the TB, it would just chirp the tires when punched at 3000 (moving at 20mph) then just haul ***.

Oh well, time for subframes and Mega-bite jr's.

[kahmi_ui]

Digital Voltmeter's are not expensive maybe 20 - 40 dollars. but you can do everything with an analog voltmeter that you can with a digital one.

[Bad89stang]

I bought a digital meter today and the TPS read .94 at idle and 4.65 at WOT. This sounds pretty good to me, but it still idles a tad too high. I reset the computer and still nothing. Do I need to adjust the idle screw? I am reluctant to do this because it idled perfectly before. I have already swithced out different TPS and IAC pieces and have had no luck. It isn't the 900 rpm idle that bothers me. It is the sticking at 1200 after I get off the gas with the clutch pushed in. It stays there for several seconds and then idles down to 900. WTF? I have checked over the surrounding vacuum lines and everything is hooked up.

[Coupe5oh]

What about the Idle screw? have you checked that yet? maybe it needs to be backed out I just realized you havent mentioned if you checked that, or im just dumb...

[PKRWUD]

Believe it or not, you don't use the idle screw to set the idle. It's really more useful for adjusting the TPS, but that's another story.

Your TPS is withing range, leave it alone.

Start the engine and let it idle for a minute, and then unplug the IAC connector. What happens?

You "switched out" the IAC with a new IAC, or another used IAC? if it's used, just remove the two screws that hold it together, and clean thouroughly with pipecleaners and CRC Brakleen (green can).

Try spraying WD-40 around the throttle body gasket, and listen for a change in idle. Is there any?

Have you tried to pull any codes? KOEO and KOER? What were the results?

This won't be too tough.

Take care,
-Chris

[RdRunnr]

Originally posted by PKRWUD
Believe it or not, you don't use the idle screw to set the idle. It's really more useful for adjusting the TPS, but that's another story.

I am sorry, but that is not true. You DO use the idle screw if you want to adjust the idle. Here are the proper steps:

- Disconnect the battery's negative for 30 minutes.
- Disconnect the plug going to your IAC
- Reconnect your battery's negative terminal.
- Start the engine, and set the idle to the rpm you want with the stop screw on the bottom of the throttle body.
Turn off the engine.
Reconnect the plug on the idle motor.
Make sure all accesories (radio, blower motor, a/c, lights, etc) are off and start the engine.
Let engine run for two minutes.
Turn engine off and wait two minutes then restart engine and let idle for two minutes with all accesories on.
If everything was done properly the computer should have learned it's new idle.

[jimberg]

That's not the correct way to set your idle, either. I think what Chris was trying to get at is that the idle is controlled by the computer and there is no way to really change it. When you adjust your idle by just turning that screw you are defeating the purpose of having an idle air bypass. The procedure for resetting the computer is correct.

On an 89, you set the idle screw by loosening the idle screw until you can fit a .010" feeler gauge between the stop plate and the end of the screw. Tighten the screw until the feeler gauge comes out with some resistance. Tighten the idle screw 1 1/2 turns more. Check your TPS to make sure it is about .95-.98V. If it checks out, reset the computer.

[Bad89stang]

O.K. I will try that method. The weird thing is the idle hanging too high when I come to a stop with the clutch in. It just sits at about 1200-1500 and then idles down to 900. What is causing that?

[stevstum]

Did you clean the T/B before you put it on the car. It sounds like it might be sticking. I would try taking it off and give it a good cleaning.

[RED92LX50]

I have first hand experience with the idle screw NOT adjusting the idle. When I first had underdrive pulleys and the stock alt, my battery was dying, and lights dimming at stop lights. So I figured I would raise my idle from 600 to about 900 (using the idle screw). It worked like a charm - until I turned the car off! When I turned it back on it idled at 600 - I was not happy.

[gtsr515]

Sell it, you don't seem to be into it enough.

[Bad89stang]

Thanks to everyone that helped on this one. It took a combination of a few words of wisdom to fix it. Here's how it was done:

1. Reset the idle screw on the TB by returning it to the factory setting. (Thanks Jim)
2. Set the TPS voltage (Thanks Chris and a few others)
3. Reset the computer (Just drove it to work and back 80miles)

The person who owned the TB before me had adjusted the idle screw way too far from the factory setting. My TPS was never the problem, but with the voltage correct I was able to eliminate it. The TB and IAC were only a few weeks old so they weren't dirty. Now it idles rock steady and returns instantly to idle when I push in the clutch when off the gas.

By the way, my father-in-law got a Ford Service Manual for his mustang off of Ebay. Everyone should have one of these! 99.9% of the car is covered. COMPLETELY. If you need to know how to do something, just look in there.

Thanks everyone