1G high idle still

[coolrider2112]

Ok. Still high idle I made sure i have no boost leaks, cleaned throttle body, plate not sticking, took throttle cable completely off so thats didnt mess with throttle. Could my tps be off I dont know how to adjust that i believe 90 dsm are different. Any help will be great thx.

 

[Beckholt99GSX]

Is your idle surging or is it just a constant high idle?

And do you have the coolant lines hooked up to your throttle body?

 

[Captn]

Do you have your ISC and FIAV? Check to make sure the ISC is plugged in, if its not that could explain the higher idle due to the BISS not being adjusted properly.


High idle at operating temps? Cold?

 

[coolrider2112]

This is high idle at at all temps cold or hot. Those vacuum ports on the throttle are blocks off except one since I use that for the boost gauge. I do not know much about ISC but looked it up and it is plugged in. Im idling at almost 2k. Is there a way to adjust the TPS or something? I can make low idle with CAS but then it runs very crappy because it would take it off 5 degree timed. Also the thing that everyone blocks off has a vaccum lined on it recirculating it back into itself, dont know what is called but its right under the throttle body and has two vaccum ports.

 

[fatal1]

Has it been high for a while or is this a more recent thing? Did you Check all your vacuum lines to see if they are hooked up right? Even if theres no leak you may have some routed incorrectly.
When you cleaned your tab, did you spray it with any fluid directly? You may have messed up the iac, there is a small hole which it gets air from in the tb and when water or liquid gets in there it could damage it

 

[bryanwheat]

How many psi did it hold and for how long when you boost leak tested it? Have you verified that the throttle cable has some slack. Did you properly adjust the biss screw?

 

[codym]

Terry's Talon Troubleshooting Tips #3 - Fast Idle (aka. Idle Surge) read that and see if any ideas solve your issue. Did you put a new gasket on with the TB ?

 

[steve]

This is high idle at at all temps cold or hot.
Im idling at almost 2k. Is there a way to adjust the TPS or something?

Also the thing that everyone blocks off has a vaccum lined on it recirculating it back into itself, dont know what is called but its right under the throttle body and has two vaccum ports.

There are two coolant lines to the FIAV (Fast Idle Air Valve). If those are disconnected and looped back then the FIAV will never receive hot coolant that closes the valve and it will cause a high idle all the time due to the extra air it provides.

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Note the two water lines coming out behind the ISC in this image from Throttlebodys.Com They run to the FIAV.

The TPS adjustment on a 90 works the same way as on the 91-94 TB. Make sure the throttle cable is loose and the throttle butterfly is closed, adjust the TPS until it outputs 0.5v +- 0.02v. Make sure the output changes smoothly with the opening and closing of the throttle. Adjust the throttle cable so that it has 1-2mm of slack.

 

[coolrider2112]

Yah my coolant lines are hooked up both of those ports that are shown are hooked up. I do have a new gasket on throttle body since someone did ask. Do you think this has anything to do with the AFPR? It is set at 37 psi right now. Just wierd after having new rod bearings and rings done my idle is higher after putting everything together.

One thing I did notice though is the one prong nipple on the throttle I believe its for grounding, I took it off and nothing happened, then I grounded to a different ground to see if that was the problem and still nothing happened.

 

[steve]

One thing I did notice though is the one prong nipple on the throttle I believe its for grounding, I took it off and nothing happened, then I grounded to a different ground to see if that was the problem and still nothing happened.

None of the nipples are for grounding. On the left side of the TB, in front of the pulley you'll see the IPS (Idle Position Switch). It has a male spade connector that grounds the signal from the ECU when the throttle is closed. For it to work correctly the TB needs to be grounded. On a 90 TB it originally was a strap from the top rear bolt holding the TB elbow and TB to the manifold to a screw on the top of the TB right by the IPS, like this.

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If the strap is missing you need to make sure you have a good ground for the IPS.

 

[coolrider2112]

So if im missing that strap you pointed out in the picture do I need to get that or is there another way to ground? The idle position sensor nipple isnt that a ground? And to see if it is working what should i do

 

[steve]

If you missing the TB ground strap, check to make sure that the Intake Manifold is grounded to the firewall (braided strap from the throttle cable adjustment bolts to the firewall) and if it is run a wire from the screw on the top of the TB to those bolts. If it's not, run a wire from the TB screw to the firewall.

With the ECU turned on check the voltage at the IPS connector with the throttle closes and with it open.
Open it should measure >5v, closed it should measure ~0v.