I still don't know if my TPS is bad!
12-14-09 | 11:53 PM
#1
I still don't know if my TPS is bad!
So i'm not really sure what i should do about my idle problem. 90' TII, rebuilt the motor myself, streetport. I'm trying to get the idle steady, but i haven't had much luck. Floods and backfires on start-up. So naturally a bad TPS could very well be the culprit.
I checked the TPS with both a multimeter for resistance, and also with the 2-tester-light adjustment method... Failed the multimeter test, and i cant get the one tester light to come back on when i open and close the throttle plates after i adjust it.
I explained this to people on a number of forums and everyone seems to say that I definately need a new TPS, But then I hear from one of the guys at ROTARY-RESURRECTION that the multimeter test is not an accurate way of testing it. He said that he has seen TPS sensors that have passed the Multimeter test but performed like crap on a running car, and some that didnt pass and worked fine on runnning cars.
So what the hell should i do? New TPS's are pricey, i just want to know for sure that its the problem.
I checked the TPS with both a multimeter for resistance, and also with the 2-tester-light adjustment method... Failed the multimeter test, and i cant get the one tester light to come back on when i open and close the throttle plates after i adjust it.
I explained this to people on a number of forums and everyone seems to say that I definately need a new TPS, But then I hear from one of the guys at ROTARY-RESURRECTION that the multimeter test is not an accurate way of testing it. He said that he has seen TPS sensors that have passed the Multimeter test but performed like crap on a running car, and some that didnt pass and worked fine on runnning cars.
So what the hell should i do? New TPS's are pricey, i just want to know for sure that its the problem.
12-15-09 | 08:07 AM
#3
HAILERS
Joined: May 2001
Posts: 20,563
Likes: 23
From: FORT WORTH, TEXAS,USA
Backprobe the green/red wire on the EM harness side of the TPS plug with the key to ON. Meter to dc volts. Slowly move the throttle linkage from idle to full open. The voltage should travel from approx one volt to somewhere around five volts. Probably closer to something like 4.8vdc or so give or take. IF it does that then it's good. Has little to do with the engines idle though. That's not its main purpose.
The one volt approx at idle is only valid for a fully HOT engine which is a bit hard to do if you remove the intercooler (time required to remove same). But a fully hot engine can be duplicated by pulling upwards on the water thermowax adjustment screw to make the fast idle cam come off it's roll pin. See book.
The one volt approx at idle is only valid for a fully HOT engine which is a bit hard to do if you remove the intercooler (time required to remove same). But a fully hot engine can be duplicated by pulling upwards on the water thermowax adjustment screw to make the fast idle cam come off it's roll pin. See book.
12-15-09 | 12:00 PM
#5
Backprobe the green/red wire on the EM harness side of the TPS plug with the key to ON. Meter to dc volts. Slowly move the throttle linkage from idle to full open. The voltage should travel from approx one volt to somewhere around five volts. Probably closer to something like 4.8vdc or so give or take. IF it does that then it's good. Has little to do with the engines idle though. That's not its main purpose.
The one volt approx at idle is only valid for a fully HOT engine which is a bit hard to do if you remove the intercooler (time required to remove same). But a fully hot engine can be duplicated by pulling upwards on the water thermowax adjustment screw to make the fast idle cam come off it's roll pin. See book.
The one volt approx at idle is only valid for a fully HOT engine which is a bit hard to do if you remove the intercooler (time required to remove same). But a fully hot engine can be duplicated by pulling upwards on the water thermowax adjustment screw to make the fast idle cam come off it's roll pin. See book.
So by 'Backprobe' you mean to measure the voltage from the red and green wires while the TPS is still plugged into the harness, right?
12-15-09 | 12:31 PM
#6
HAILERS
Joined: May 2001
Posts: 20,563
Likes: 23
From: FORT WORTH, TEXAS,USA
A green wire with a red stripe on it and all connectors connected together. NOT two seperate wires green and red.
The FSM states that the narrow range TPS plunger should output APPROX 1vdc at idle (engine fully HOT). Then open the throttle slowly to full open and the FSM states it should read approx 5vdc. The 4.85vdc is APPROX and just fine and dandy.
The engine does not have to be idling to do this. Just key ON and a fully HOT engine and if turbo it might help to lift up on the water thermowax screw to seperate the cam and roll pin so the throttle plates close completely.
The two LED light method is just fine. The end result is ..........an output of the narrow range TPS of approx one volt dc.
The FSM states that the narrow range TPS plunger should output APPROX 1vdc at idle (engine fully HOT). Then open the throttle slowly to full open and the FSM states it should read approx 5vdc. The 4.85vdc is APPROX and just fine and dandy.
The engine does not have to be idling to do this. Just key ON and a fully HOT engine and if turbo it might help to lift up on the water thermowax screw to seperate the cam and roll pin so the throttle plates close completely.
The two LED light method is just fine. The end result is ..........an output of the narrow range TPS of approx one volt dc.
12-16-09 | 06:17 PM
#7
A green wire with a red stripe on it and all connectors connected together. NOT two seperate wires green and red.
The FSM states that the narrow range TPS plunger should output APPROX 1vdc at idle (engine fully HOT). Then open the throttle slowly to full open and the FSM states it should read approx 5vdc. The 4.85vdc is APPROX and just fine and dandy.
The engine does not have to be idling to do this. Just key ON and a fully HOT engine and if turbo it might help to lift up on the water thermowax screw to seperate the cam and roll pin so the throttle plates close completely.
The two LED light method is just fine. The end result is ..........an output of the narrow range TPS of approx one volt dc.
The FSM states that the narrow range TPS plunger should output APPROX 1vdc at idle (engine fully HOT). Then open the throttle slowly to full open and the FSM states it should read approx 5vdc. The 4.85vdc is APPROX and just fine and dandy.
The engine does not have to be idling to do this. Just key ON and a fully HOT engine and if turbo it might help to lift up on the water thermowax screw to seperate the cam and roll pin so the throttle plates close completely.
The two LED light method is just fine. The end result is ..........an output of the narrow range TPS of approx one volt dc.
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