North American Turbocoupe Organization



ECU re-set question
Cullen Offline
Junior Member
#1
I am trying to test and set the Throttle Position Sensor on my 2.3 liter turbo fuel injected engine.

For an initial setting, in what position do I tighten the two screws on the TPS?

Secondly, once I have it set in position and tested ( .9 volts at idle and smoothly up to about 5 volts at full throttle ) is there a waiting time or number of engines hours required for the ECU to re-set itself to any changes?
One item I read seemed to indicate there would be a re-set period before the ECU caught up with the change.

Thank you all.
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Jeff K Offline
Administrator
#2
No point to try some initial TPS adjustment until you have a DMM hooked up to monitor TPS voltage.

Engine does NOT need to be running to set TPS voltage..... you just need the key in the RUN position.

FYI, WOT TPS voltage will typically be 4.6 V or so, not super close to 5.0 V.

The ECU does NOT have a learning period when TPS is adjusted or replaced. On a MAF car (our VAM system qualifies as a primitive MAF system) all TPS really does is tell the ECU if throttle is at idle, at part throttle, or at WOT.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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Cullen Offline
Junior Member
#3
Thanks.
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Cullen Offline
Junior Member
#4
Another question,

I tested the Throttle a Position Sensor by using a voltage test across the center terminal (the TP signal) and battery ground. I get no voltage at all, in any throttle position. Then I check the resistance across all terminals and get NO resistance between any terminal nor does the resistance change when I rotate the control on the sensor. 

Does anyone know if the sensor is basically a variable resistor? If so, it should show resistance and variable resistance when rotated if it is good. 

I have another TPS that was sent to me as the wrong year and will not fit. I get the same NO resistance readings on it too.
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Jeff K Offline
Administrator
#5
Check TPS volts between TPS output (green) and SIGNAL RETURN (black). Signal return and chassis ground are NOT the same!!! If still no voltage, check for 5.0 V +/- .1 V (this is VREF, sensor reference voltage, orange wire) between orange and black wires.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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Cullen Offline
Junior Member
#6
I checked these readings and the most I got was .4 volts. I followed the orange wire back to the barometric reading sensor and it too had an output of .4 volts. The input on the barometric sensor was .6 volts. These should have been 4.5 volts to 5 volts. I followed that wire back to pin #45 on the ECU and that output was only .6 volts also.

Seems my ECU may have a bad section. I have had Frankenstein running / driving and ran well. After about 75 test miles I noticed an oil leak near the drivers rear of the head (the oil passage to the OHCam ). So I changed the head gasket. Since, it runs and drives but has a flat spot in the acceleration at 1/3 pedal. I am going to check the fuel pressure and have already checked almost everything else. I did not take any wiring or vacuum lines loose in the gasket change but have double checked them.

It is perplexing that it ran so well, scary fast and now has a hitch. It is for sure the ECU is not correct so I will get a reconditioned unit. All said, it would seem that if it ran on the “old” 87 ECU so well before the gasket change, it is not the ECU but the voltages say otherwise.

One problem that comes along with Frankenstein is the 85 Throttle Position Sensor has to be an 85 but the wiring followed an 87 ECU diagram. An 87 TPS will not fit my 85 intake. 

I will get this hitch resolved too but any guidance that would cause me to investigate something may be the help I need.
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Cullen Offline
Junior Member
#7
When I changed the head gasket, I did have the battery positive disconnected so I did not fry the ECU. The engine runs on the old, used 87 ECU but barely runs on the 85 reconditioned ECU.
Just a bit more info.
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anasazi4st Offline
Senior Member
#8
(06-02-2020, 10:26 PM)Cullen Wrote: When I changed the head gasket, I did have the battery positive disconnected so I did not fry the ECU. The engine runs on the old, used 87 ECU but barely runs on the 85 reconditioned ECU.
Just a bit more info.
Get some Map pins—the ones with the large round colored heads—and carefully push each into each of the connector’s wires, BACK INTO the rubber/plastic of the connector, so as not to expose the wires by breaking their insulations. This makes it MUCH easier to connect alligator clips to those wires for testing.
Another proud dues-paying member.

1987 Turbo Coupe w/T5OD, 8.8 axle, grey smoke; most options. Got it in 1991 with 41K miles: 3 turbos, 2 heater cores, 1 T5OD full rebuild, 5 clutches, 1 head gasket, 2 Teves II ABS units, etc. later....
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Jeff K Offline
Administrator
#9
I am so used to using a good scan tool to look at PIDs on our newer OBDII junk that I thought it would be nice to be able to easily monitor various sensor outputs on my OBDI 88 TC and 86 Tbird 5.0........ so what I did a few years ago to make it easy to check TPS volts, etc, etc.........

I bought a bunch of ATO fuse holders with the snap on covers cheap from Amazon. Took them and spliced into TPS output, BARO output, ECT and ACT/IAT outputs, VAF and VAT outputs and SIgnal Return on the TC, and MAP, ACT/IAT, TPS ECT, EVP and SIgnal Return on the 86 5.0.

Then took a ATO fuse, and purposely blew the fuse with my bike battery. Used a Dremmel to grind down the terminals on the top of the blown fuse and soldered wires to the top of the fuse, Other ends of the wires go to banana plugs for my Fluke DMM (Big $$ meter but worth every cent). All I have to do is plug the blown fuse with the wires / bananas attached into the fuse holder of the circuit I want to monitor. WIres from blown fuse to DMM are long enough I can run them into the car and see the sensor outputs on my DMM while driving if I want to. For things like ECT/VAT/IAT/ BARO/MAP took sensor voltage / frequency data and made a bunch of Excel graphs using date from the Ford shop manuals to map voltages to temperatures, pressure, etc.

Not as easy as monitoring actual values with a good OBDII scan tool, but has come in VERY handy for troubleshooting!!
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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