TPS Test Question
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TPS Test Question
I am still scratching my head over the rough idle on my '89 302.
Last night I ran the codes and nothing showed (with the exception of some E4OD codes...I am running a '92 EEC from a donor that had an E4OD).
I decided to check the TPS-what I did was take a long skinny probe from my digital meter and insert it in the backside of the 12v feed to the TPS and ran the other to the neg term of the battery. Turned the key to run and it measured .88v. From what I have read, that is low, it should read .95-.99v.
My question is, how do I adjust the TPS? I am thinking remove the TB, loosen the TPS and move it until the voltage reads correct value. Am I on the right track?
If that is the proceedure, should all I need is a new gasket?
Dan
Last night I ran the codes and nothing showed (with the exception of some E4OD codes...I am running a '92 EEC from a donor that had an E4OD).
I decided to check the TPS-what I did was take a long skinny probe from my digital meter and insert it in the backside of the 12v feed to the TPS and ran the other to the neg term of the battery. Turned the key to run and it measured .88v. From what I have read, that is low, it should read .95-.99v.
My question is, how do I adjust the TPS? I am thinking remove the TB, loosen the TPS and move it until the voltage reads correct value. Am I on the right track?
If that is the proceedure, should all I need is a new gasket?
Dan
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From: The dark carnival
As far as the TPS...here is the deal. You want a minimum voltage at closed throttle over .49 vdc. If you have less than .49 volts then codes 23 and 63 will set as failures. The voltage at closed throttle should not exceeed 1.2 vdc...if it does then codes 23 & 53 will set as failures. You want to see voltage increase of .04 vdc from the minimum registered to id part throttle status in the computer. You also want to see a minimum WOT value of 3.2 vdc and not higher than actual voltage reference (VREF) generated by the ECM. There is no 12 volt feed to the TPS....there should be a VREF of 5 volts, a ground and a signal wire....so I don't know what you are talking about regarding the 12 volts.
Even though the TPS varies voltage, the system only uses it to establish 3 states. Closed Throttle, Part Throttle and WOT by the voltage min-max values to set a code, minimum to determine WOT (=2.71 vdc over minimum closed throttle setting), and by monitoring TPS voltage change to determine acceleration/steady/deceleration status...among other sensors inputs like the MAF and VSS. So, if you are trying to diagnose a rough idle, I think you are looking in the wrong area.
The normal setting for a TPS @closed throttle, would be between .7 vdc and 1.0 vdc, allowing a .2 vdc window up or down for variance caused by thermal stress and charging system variability. So....if your closed throttle TPS signal voltage falls within .7 vdc and 1.0 vdc.....no need to adjust.
Even though the TPS varies voltage, the system only uses it to establish 3 states. Closed Throttle, Part Throttle and WOT by the voltage min-max values to set a code, minimum to determine WOT (=2.71 vdc over minimum closed throttle setting), and by monitoring TPS voltage change to determine acceleration/steady/deceleration status...among other sensors inputs like the MAF and VSS. So, if you are trying to diagnose a rough idle, I think you are looking in the wrong area.
The normal setting for a TPS @closed throttle, would be between .7 vdc and 1.0 vdc, allowing a .2 vdc window up or down for variance caused by thermal stress and charging system variability. So....if your closed throttle TPS signal voltage falls within .7 vdc and 1.0 vdc.....no need to adjust.
Last edited by eco; Nov 28, 2007 at 08:11 PM.
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Joined: Oct 2006
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From: Redmond, WA
Originally Posted by dbf288
I am still scratching my head over the rough idle on my '89 302.
Last night I ran the codes and nothing showed Dan
Last night I ran the codes and nothing showed Dan
Idle fluctuations are fun ain't they! Buy, beg, borrow or steal a vacuum gauge and test your vacuum lines. One cracked line can cause this idle fluctuation.
Clean your IAC valve.
If the truck is old and beat...
Pour a half a can of seafoam in the brake booster while running AND after the motor has reached operating temperature. Turn off the truck. Wait 15 minutes and run the truck again. This will clean up any excessive carbon build up on the top half of your motor. The stuff works great for old rigs... chebby's, mopars and good ol'd Ferds.
Pour the other half in your tank.
Your TPS is reading just fine.
check up on www.fordfuelinjection.com to learn how each EFI sensor works and how they should test.
Good Luck,
Mike
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ECO, thanks for the explaination. When I referred to the 12v input, I meant the reference voltage input. Sorry for the mis-information/confusion.
I cannot remember exactly what the numbers were when I tested yesterday with my digi meter, while sweeping through closed, part and WOT, but I can say it fit within the parameters you stated. I wish I had an analog meter, I tend to do better with needle sweep rather than looking at numbers. Based on what you stated, I will continue my troubleshooting elsewhere.
Mike, I cleaned the IAC, whith copious amounts of TB cleaner. Initially, the crap that ran out was very dark (dirty). By the time I repeated the flush, soak and "drain" cycle about 5 times, the fluid running out was clear. I do however, suspect the solinoid that drives the IAC is weak. I have another IAC lying around. I just might try swapping solinoids and see what happens.
I doused the intake with a full can of seafoam. I sucked in 1/2 the can, let it set for 1/2 hour and repeated the process. It smoked like a banshee afterwards. I did find a noticable difference in throttle responce. When I kick it into passing gear, she takes right off-so to speak!
I will see about checking vacuum lines...I am still wondering about coolant or air charge sensors though??
Dan
I cannot remember exactly what the numbers were when I tested yesterday with my digi meter, while sweeping through closed, part and WOT, but I can say it fit within the parameters you stated. I wish I had an analog meter, I tend to do better with needle sweep rather than looking at numbers. Based on what you stated, I will continue my troubleshooting elsewhere.
Mike, I cleaned the IAC, whith copious amounts of TB cleaner. Initially, the crap that ran out was very dark (dirty). By the time I repeated the flush, soak and "drain" cycle about 5 times, the fluid running out was clear. I do however, suspect the solinoid that drives the IAC is weak. I have another IAC lying around. I just might try swapping solinoids and see what happens.
I doused the intake with a full can of seafoam. I sucked in 1/2 the can, let it set for 1/2 hour and repeated the process. It smoked like a banshee afterwards. I did find a noticable difference in throttle responce. When I kick it into passing gear, she takes right off-so to speak!
I will see about checking vacuum lines...I am still wondering about coolant or air charge sensors though??
Dan
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Joined: Oct 2006
Posts: 843
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From: Redmond, WA
Originally Posted by dbf288
.
I doused the intake with a full can of seafoam. I sucked in 1/2 the can, let it set for 1/2 hour and repeated the process. It smoked like a banshee afterwards. I did find a noticable difference in throttle responce. When I kick it into passing gear, she takes right off-so to speak!
I will see about checking vacuum lines...I am still wondering about coolant or air charge sensors though??
Dan
I doused the intake with a full can of seafoam. I sucked in 1/2 the can, let it set for 1/2 hour and repeated the process. It smoked like a banshee afterwards. I did find a noticable difference in throttle responce. When I kick it into passing gear, she takes right off-so to speak!
I will see about checking vacuum lines...I am still wondering about coolant or air charge sensors though??
Dan
Glad to see the seafoam worked out. Try a can through your tank as well.
Good luck
Mike
