Fox 1993 FOX High Idle

TheJay806 · Dec 24, 2024

My fox idles consistently smooth, drives fine, etc no issues with surging at all. However, it stays idling at 1000rpm all the time and will not go lower for the life of me. I did adjust the throttle stop screw, and I wish I wouldn't have but, I did. I have it back as close as I can get it right now an its at the 1000rpm. I tried replacing the IAC and TPS. The new IAC made it idle even higher so I went back to the old one. Has the new TPS with correct Voltage now. I noticed yesterday, that the Throttle Plate has a hole in it. Not sure if it was drilled previously or came that way. I'm assuming that may be why it won't idle below the 1000rpm? With the Throttle screw backed all the way, still at 1000rpm, unplug IAC, no change. Unplug MAF car almost dies of course. Drives and Idles fine, its just high idle. Tried finding vacuum leaks with Carb Cleaner and couldn't not find anything. This car has the EGR hoses capped off, was like that when I got it. Cleaned throttle body, etc. Any help is appreciated, I know this topic has been addressed 100 different ways.

Mustang5L5 · Dec 24, 2024

Unplug the IAC, back the throttle stop screw out. It should idle down and die.

If it doesn’t, you have a vacuum leak. Time to get a smoke machine and smoke the system out to find it. You can also try spraying carb cleaner around to see if the idle raises up.

TheJay806 · Dec 24, 2024

Thank you, sounds like it'll be a vac leak. When throttle screw is all the way backed out and IAC unplugged, there's 0 change in idle. I tried spraying carb cleaner around the vac hoses I could find with nothing revving the idle but I'm sure I missed one somewhere

Noobz347 · Dec 24, 2024

Check up against the firewall and underneath the dash on the passenger side where it runs into the HVAC.

Have you pulled codes?

TheJay806 · Dec 24, 2024

I'll check there now, the only code I got was 13.

Noobz347 · Dec 24, 2024

TheJay806 said:
I'll check there now, the only code I got was 13.

Sounds like you're on the right track then.

AeroCoupe · Dec 24, 2024

Typically a hole drilled on the throttle body blade was a bandaid for an isle issue. I’d look at replacing the TB and go through the base idle reset once I knew everything else was good to go.

KRUISR · Dec 25, 2024

Did you unplug the SPOUT connect and the IAC when adjusting the throttle stop. If you don't do both it won't do the job fully. Also, did you do the relearn steps for the idle after? If you change your IAC valve you may have to do the base idle reset again (if the new one has a different range of motion).

Before replacing the throttle body, remove and inspect the blade for any holes a previous owner or mechanic may have put in it.

For a Base Idle Reset procedure that I have found works well for me, go to post #9, the steps are at the bottom of the post.

Thread 'Base Idle Reset'

Oct 10, 2020

I'd like to post this for all the newer mustang owners and the others like me that never took the base idle reset seriously. I've had multiple engines and various setups but never once done the base idle reset. I just replaced the lifters in my car after having one collapse. I thought the bottom end had come apart because of the violent knocking coming from it.
So I did what some of us typically do. I turned a two day protect into a couple week extended project. There's a few rules in my projects. Never put fasteners back in without wire brushing them. This helps them go back in...

Noobz347 · Dec 25, 2024

KRUISR said:
Did you unplug the SPOUT connect and the IAC when adjusting the throttle stop. If you don't do both it won't do the job fully. Also, did you do the relearn steps for the idle after? If you change your IAC valve you may have to do the base idle reset again (if the new one has a different range of motion).

Before replacing the throttle body, remove and inspect the blade for any holes a previous owner or mechanic may have put in it.

For a Base Idle Reset procedure that I have found works well for me, go to post #9, the steps are at the bottom of the post.

Thread 'Base Idle Reset'

Oct 10, 2020

I'd like to post this for all the newer mustang owners and the others like me that never took the base idle reset seriously. I've had multiple engines and various setups but never once done the base idle reset. I just replaced the lifters in my car after having one collapse. I thought the bottom end had come apart because of the violent knocking coming from it.
So I did what some of us typically do. I turned a two day protect into a couple week extended project. There's a few rules in my projects. Never put fasteners back in without wire brushing them. This helps them go back in...

Wayne Waldrep

Replies: 15

Forum: 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-

Pro Tip:

If you go to the number in the upper RH corner of the post you can click on --or-- copy the link from the post to put your reader directly on that post:

Link to Post 9

Post in thread 'Base Idle Reset'

Jan 16, 2021

Ok, I'm going to just post this and be done with the base idle reset deal.
If you are just learning and look around for instructions on this, it's not clear. For example, if I'm looking for instructions or a YouTube vid on installing an intake, I'm not going to watch a video on rebuilding an entire engine. If I want to use that person's instructions, I'd obviously skip to the intake part. Why in the world would I go thru the rest?
Like I stated above, @jrichker contributions to this site are excellent and appreciated. Nothing I do comes close to his detail. When I was doing my...

Mustang5L5 · Dec 25, 2024

AeroCoupe said:
Typically a hole drilled on the throttle body blade was a bandaid for an isle issue. I’d look at replacing the TB and go through the base idle reset once I knew everything else was good to go.

But stock TBs have the hole present, so hard to say if he’s looking at someone’s band-aid fix, or just a stock TB blade with a hole present.

Stoxk hole here

AeroCoupe · Dec 26, 2024

Did not know the stock ones have the hole so learned something today.

Just had a tuner drill my 70mm BBK without asking and the car still did not idle right. Put a new one on and took it to another tuner and he nailed the tune.

I think the bigger part of this is setting the TB stop screw where it gets enough metered air to idle where your cam will let it idle, check TB sensor voltage, and then perform a base idle reset.

Noobz347 · Dec 26, 2024

AeroCoupe said:
Did not know the stock ones have the hole so learned something today.

Just had a tuner drill my 70mm BBK without asking and the car still did not idle right. Put a new one on and took it to another tuner and he nailed the tune.

I think the bigger part of this is setting the TB stop screw where it gets enough metered air to idle where your cam will let it idle, check TB sensor voltage, and then perform a base idle reset.

Not mention that in all my years, I've purchased maybe half a dozen throttle bodies from various companies. Of those, I have returned for defects, every single one except the 80mm Accufab that I run for the KB.

Quality Control issues in the 21st Century are real.

TheJay806 · Dec 28, 2024

Noobz347 said:
Sounds like you're on the right track then.

Did a smoke test today, seems to be leaking from where the orange gasket is at the EGR valve. And light smoke from the center of the Throttle position sensor. EGR is connected but hoses are capped off. Pictures attached.

Noobz347 · Dec 28, 2024

That "orange gasket" is the EGR diaphragm itself. You need a new EGR valve.

TheJay806 · Dec 28, 2024

This leak is most likely keeping me at 1000rpm in your opinion? Also, just the EGR, I prob don't need the sensor, or easier to just do both?

Noobz347 · Dec 28, 2024

TheJay806 said:
This leak is most likely keeping me at 1000rpm in your opinion? Also, just the EGR, I prob don't need the sensor, or easier to just do both?

Ah, your second small leak.

Swap the EGR valve first. The EGR operates at idle and will cause you issues.

As for your leak at the TPS:

Maybe somebody could chime in about the TPS sensor shaft and whether or not it is sealed or has a seal?

TheJay806 · Dec 30, 2024

Would plating off this EGR be off any benefit? Or better to just replace it?

Noobz347 · Dec 30, 2024

TheJay806 said:
Would plating off this EGR be off any benefit? Or better to just replace it?

It is better just to replace it. They are not very expensive.

Noobz347 · Dec 30, 2024

@General karthief @Mustang5L5 @AeroCoupe @a91what @90sickfox

Do any of you know if there is a shaft seal for the TPS sensor shaft on the TB?

AeroCoupe · Dec 31, 2024

Throttle bodies have the seals so if you are getting blow by it’s time for a TB. They don’t typically sell seal kits and most only warranty for a year. At least this is my experience.

Fox 1993 FOX High Idle

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Stangnet Facilities Maint Tech... Er... Janitor

lube between the nut and the face. I know my lubes

Stangnet Facilities Maint Tech... Er... Janitor

That is…until I whipped out my Bissell

lube between the nut and the face. I know my lubes

Stangnet Facilities Maint Tech... Er... Janitor

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lube between the nut and the face. I know my lubes

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