I have a 91 mustang with the on3 performance turbo kit on it. My timing is set at 10, fuel is good, no vacuum leaks. The car will idle fine but will not return to idle after rev. Any ideas?
Thanks

 

some turbo cars have problems idling. what throttle body do you have? some give you a srew to help adjust idle. if not you can clock your mass air in a different spot and that might help it too.

 

how old are the O2 sensors?

 

How the MAF is clocked can make an idle issue. First remove your IAC, located on the front of the throttle body. Completely take this IAC apart and clean it really thorough with carb cleaner. Re-install it. Is there alot of build up inside the TB?

 

Thanks for the tips. Im gonna try them out tommorow. The TB is a 65mm professional products and it is in good working order. As far as the O2 sensors they have no use on my car but being plugs. I adjusted the TB to a high idle about 1300rpm anyone see any problems with that for now? Fuel economy is not what im going for....I just don't want to have to worry about the car stalling and looking like an idiot

Does anyone know if the pony down Y pipe will fit the on3 performance downpipe and hook up to the catbacks?

Thanks

 

What I am bout to say may sound like a pain in the ass but everytime you adjust the throttle, the TPS voltage needs to be reset. It has been so long since I have done it, all I can remember is that the voltage needs to be set at 0.99. If the voltage is off (and it will be whenever the idle is adjusted) then it will tell the computer that the TB is or isn't open all the way therefore miscalculating the fuel and timing. Just the heads up.

 

I have no idea what you're doing if you don't have your O2 sensors hooked up.
Care to explain so people can answer accordingly?

 

Check the tps voltage.Should be between .94-.98 volts. Disconnect your battery for 20 minutes or so......unplug the iac.... reconnect battery start car...set idle speed with the idle screw...then plug the iac back in.Idle should be set around 800.

Also the salt and pepper shakers can cause the same problem. You can take those apart and clean them and put some dielectric grease on them.

 

Thanks! and nevermind the comment about the o2 sensors, I was being there

 

Also make sure the throttle cable isnt hanging up on ya.They do tend to get sticky after awhile. Just another thought.

 

A LOT of times, it turns out to be just old O2 sensors causing it.
Say it will idle fine, then just jump up and search around for an rpm, then do what ever it wants sometimes.
Probably O2 sensors.
If they have 50K on them with junk gas, they're needing replacement.

 

Can some one please hold my hand like a small child about which wire to get my tps voltage from and the exact proceedure? thanks for the help...I changed the o2 sensors and cleaned the air bypass and it seems to be running better, haven't drove it yet but it will rev and return to idle now. Thanks for all the help so far!

 

Red on your voltmeter will go on the green wire and the black you can use a good engine ground or the black wire on the tps.

What I ususally do is pierce the green wire with the point of the voltmeter and the same for the black wire.

Make sure the key is on and not started.Then if you can open the throttle to wide open make sure it reads IIRC 4.00volts.

 

Yep, green wire and a good ground will do. .99 volt at idle and 4.50+ volts at WOT and smooth voltage drop the whole way down. If it has dead spots then replace the TPS. Also do you have any codes stored??

 

The TPS can read anywhere between ~ .6v and 1.2v and still be good. If it is outside of that range, it's in need of replacement...not adjustment. The TPS sensor is non adjustable...and at power-on the ECU takes the inital sensor reading as it's base.

Again, don't adjust the TPS.

 

I THINK this is false.

The TPS IS adjustable. AND, it controls how rich/lean the motor runs at idle mostly.
I didn't think the computer resets itself each time it has power to the tps.

someone correct me

 

Ok....

http://www.veryuseful.com/mustang/tech/engine/Mustang-TPS-FAQ.html

http://fordfuelinjection.com/?p=30

https://www.fordtruckzone.com/artic...PS_throttle_position_sensor_ECM_code_124.html

 

so the computer uses the O2 sensors to find it's air/fuel ratio at idle, no matter what the tps says after restarting (as long as tps is within range)?

 

You got it. Keep in mind too that the computer uses it's base table as well as the long term KAM first....and the 02's readings are applied to those. This of course only happens once the 02's warmup and the engine is in closed loop operation.

 

The problem is he has a professional products tb.Not a ford tb.

http://www.professional-products.com/PDF Instructions/69200_69210_Instructions.pdf

If you read the instructions for his tb it needs to be adjusted.