throttle issues - MustangForums.com


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Old 08-10-2018, 11:16 AM   #1  
lurch69
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Join Date: Jun 2013
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Angry throttle issues

I have a 89 with 302 with trick flow upper package (heads,intake and cam) with 70mm throttle body 24ilb injectors.(yes, for now its a stock computer)
I having a issue that the engine revs up by itself and some cases that I turn it off and back on it stabilize.
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Old 08-11-2018, 07:39 AM   #2  
wbrockstar
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Have the mods been in place for awhile and this symptom just popped up out of nowhere or did you just install them and that's what triggered the symptom??

Possible causes :
1) Defective tps
2) A dirty or defective iac valve
3) The throttle body idle set screw is out of adjustment
4) Vacuum leak
5) Dirty or defective egr valve

The symptom clearing up temporarily once the engine is shut off then restarted is a typical symptom of a defective or noisy tps.The tps closed throttle voltage resets everytime
the key is turned off then back on again.Vref voltage (orange and black/white wire) should be close to 5.0 volts,koeo.
Signal voltage (green and black/white wire) should be .50-1.19 volts closed throttle with the koeo.Voltage spikes/dead spots should not be present when opening the throttle from a closed to wot to closed position.Lightly tap on the tps with a screwdriver handle during this test to verify vibration isnt affecting the tps.WOT voltage should be lower than Vref voltage.

The iac valve can cause the symptom when it gets dirty or when it's defective.

To check the egr valve,remove the vacuum hose from it,plug the hose then take the car for a short test drive.If the rough idle/ running symptom clears up,the egr valve is sticking open because it's dirty or defective or the evr solenoid is defective.

Vacuum leaks can be present in hoses,gaskets,injector orings,egr valve diaphragm,vacuum operated components,etc.If the engine is idling and carb cleaner or propane is introduced to an area where a leak is present, the engine idle will surge.

If the rough idle can also occur if the idle set screw is out of adjustment.A base idle reset procedure can be done if the mechanical idle value is out.With the engine idling,disconnect the harness from the iac valve.The engine should stall or the idle should drop.If not,the iac is dirty /defective or the idle set screw is out of adjustment.The base idle reset link is listed below.


http://sbftech.com/index.php/topic,1031.0.html

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Old 08-11-2018, 09:34 AM   #3  
lurch69
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Join Date: Jun 2013
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Posts: 17
Thumbs up Thanks for the info.

[QUOTE=wbrockstar;8631276]Have the mods been in place for awhile and this symptom just popped up out of nowhere or did you just install them and that's what triggered the symptom??

Possible causes :
1) Defective tps
2) A dirty or defective iac valve
3) The throttle body idle set screw is out of adjustment
4) Vacuum leak
5) Dirty or defective egr valve

The symptom clearing up temporarily once the engine is shut off then restarted is a typical symptom of a defective or noisy tps.The tps closed throttle voltage resets everytime
the key is turned off then back on again.Vref voltage (orange and black/white wire) should be close to 5.0 volts,koeo.
Signal voltage (green and black/white wire) should be .50-1.19 volts closed throttle with the koeo.Voltage spikes/dead spots should not be present when opening the throttle from a closed to wot to closed position.Lightly tap on the tps with a screwdriver handle during this test to verify vibration isnt affecting the tps.WOT voltage should be lower than Vref voltage.

The iac valve can cause the symptom when it gets dirty or when it's defective.

To check the egr valve,remove the vacuum hose from it,plug the hose then take the car for a short test drive.If the rough idle/ running symptom clears up,the egr valve is sticking open because it's dirty or defective or the evr solenoid is defective.

Vacuum leaks can be present in hoses,gaskets,injector orings,egr valve diaphragm,vacuum operated components,etc.If the engine is idling and carb cleaner or propane is introduced to an area where a leak is present, the engine idle will surge.

If the rough idle can also occur if the idle set screw is out of adjustment.A base idle reset procedure can be done if the mechanical idle value is out.With the engine idling,disconnect the harness from the iac valve.The engine should stall or the idle should drop.If not,the iac is dirty /defective or the idle set screw is out of adjustment.The base idle reset link is listed below.


http://sbftech.com/index.php/topic,1031.0.html[/QUOTE

Thanks for the information.
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