TPS & Base Idle Reset

[Noobz347]

Only regurgitating what I learn here from y'all

That's my job!


Wait...



You do it!

 

[CAMTWO1070]

The computer doesn't care about the TPS voltage as long as during the initial key on it's somewhere within .5 to 1.25 volts. Your idle is too high with the IAC unplugged. The computer wants to be able to control the idle with the IAC at around 30% duty cycle, and the computer is programmed to want to idle at 672 RPM. This is why custom tuning is necessary to achieve a smooth idle at a higher RPM if you have a big cam. There are functions in the computer that need adjusted to achieve that, and not upset it.

YEP and the most critical is the fuel injection timing table especially if you arent running the stock camshaft.....................

For my 351w with Explorer camshaft I had to rescale the fuel injector table by 20 to be in spec with the intake valve opening events.......

The top is the setting for my 351w and the stock 302 is on the bottom..

 

[Nostang25]

Just tried BIR and got it to idle great with the IAC unplugged but when I plugged it back in and started the car up the idle was rising over 2k.

Shut er down and backed out the throttle screw. Gonna check the tps tomorrow with a multimeter.

Any other suggestions?

 

[AeroCoupe]

Three things I would suspect:

1) Vacuum leak
2) Throttle stop is set incorrectly
3) Bad IAC

 

[KRUISR]

Three things I would suspect:

1) Vacuum leak
2) Throttle stop is set incorrectly
3) Bad IAC

This, in this order. Ideally you can set the idle with IAC and SPOUT unplugged below 650 rpm (it will run like a bag of sh!t) but as long as it can run, the lower the better. The lower you get it the more working range the IAC has to try and keep idle smooth.

Once vac leaks are fixed, throttle stop will need to be opened slightly (no more air downstream getting in).

 

[AeroCoupe]

Also, the engine has to be a closed system and if unmetered air is getting into it that will also cause problems. I had this issue with regards to the oil filler cap here:

Engine Post in thread 'Occasional misfires normal for a HCI?'

Jan 30, 2023

Change the temperature sending unit. Mine did that and I put a new one in and the gauge went back close to where I was used to it being. Also, these cars came stock with a 192 deg F thermostat so running a colder one will move the needle.

Sounds like your fuel system is good to go. PCV system is pretty basic in that as long as the check valve is working and has a good seal the lower intake you should be good to go.

I noticed you have Motorsport valve covers. What did you do to replace the oil fill neck on the passenger side valve cover? Reason I ask is on mine I had a push in cap...

• AeroCoupe

• 

 

[Nostang25]

Also, the engine has to be a closed system and if unmetered air is getting into it that will also cause problems. I had this issue with regards to the oil filler cap here:

Engine Post in thread 'Occasional misfires normal for a HCI?'

Jan 30, 2023

Change the temperature sending unit. Mine did that and I put a new one in and the gauge went back close to where I was used to it being. Also, these cars came stock with a 192 deg F thermostat so running a colder one will move the needle.

Sounds like your fuel system is good to go. PCV system is pretty basic in that as long as the check valve is working and has a good seal the lower intake you should be good to go.

I noticed you have Motorsport valve covers. What did you do to replace the oil fill neck on the passenger side valve cover? Reason I ask is on mine I had a push in cap...

• AeroCoupe

• 

I worked on it this evening and got the idle down to 700, feels and sounds way better!

I checked my tps voltage and it was up at 1.36. Messed with it but could only adjust to 1.15. I have read and seen that the magic number is somewhere between .97 and .99, but I can’t get there. Is this a serious issue worth getting a new tps?

Also, now my gas pedal sticks at the top. Very annoying!

 

[gkomo]

The .99 is a myth, the range is much wider for proper operation. 1.35 does sound like it was out of the good range, but bringing it down to 1.15 should be within the range. I’ve heard like .65 - 1.25 but don’t quote me on that.

 

[AeroCoupe]

I typically shoot for the 0.80 to 1.0 range just to keep it inside the parameters for wear and tear over time. If you cannot get it there with slotting the holes then I would get a different one but that’s me.

Here you go:

Post in thread 'TPS & Base Idle Reset'
https://stangnet.com/mustang-forums/threads/tps-base-idle-reset.929965/post-9436329

 

[JMG9350]

The Foxbody EEC4 computer looks for the TPS voltage range to be between .5 and 1.25 volts during key on. As long as it's somewhere in that range, and stays there during ignition on, it will read that as closed throttle.