The ECI/ECU (your computer) gets 12 volts POSITIVE
thru the SECOND fusible link. What condition is the fusible link in? Rolling Eyes
The male/female spades are NOTORIOUS for CONTAMINATION! Mad

The ECI/ECU gets it GROUND from #11 ground.

The TPS (throttle position sensor) tells the ECU where your foot is on the throttle and uses that info to determine how long the ON PULSE to your injectors should be.

Yes, It determines the A/F RATIO!

They are known to be WORN-OUT about 100k miles! Performing TWO ohm test will determine if yours need replaced. You MUST have a AVOM meter (a meter with a needle) to perform the “SWEEP TEST!”

The “SAS Fixed” screw is what the DEAD-STOP…or REST POSITION for the butterfly is.

In the 88 factory service, pages 14-32 thru 14-35, is how you ADJUST your TPS.

As you can see…there is a bracket that blocks easy access to that screw
(in red) because…if you turn it, the TPS will need re-adjusted!

The instructions in those pages…are how to RETURN IT TO WHERE IT SHOULD BE! Shocked

Most of the used TBs I have come across are in a VIRGIN STATE and that’s GOOD NEWS! Cool


The screw on the left is the ISC adjusting screw…and *YOU* are NEVER to back-it-out! It merely adjust the ISC STOPPER LEVER to MAKE SURE the ISC GROUNDS the ISC when it is returned to IDLE!


NO POWER IS NECESSARY…when you perform 2 OHM TEST.
And…you can do it while you hold your TPS in your HAND. Rolling Eyes

And…you ATTACH your AVOM direct to the FEMALE CONNECTOR…NOT THREW A ADAPETER HARNESS!!!! (same as FSM injector OHM test)

The “ADAPTER HARNESS” is *ONLY* used to SET/ADJUST the IDLE VOLTAGE (key “on”, engine idling) to .48 to .52 *VOLTS*…..if it PASSES THE “SWEEP-TEST”.

Once the idle voltage is properly adjusted….as you INCREASE the THROTTLE, the voltage *SMOOTHLY* INCREASES to about 4.5-4.8 volts.

Testing/inspection is a RESISTANCE NEEDLE “SWEEP” TEST using a AVOM ONLY!
Sorry, but you’ll need a NEEDLE to do this test. ALWAYS CALIBRATE THE AVOM FIRST. Wink


The top terminal is “TERMINAL ONE”. In a clockwise direction, the next is “TERMINAL TWO”……..followed by “TERMINAL THREE”.

After you attach a couple of trimmed 14 gauge male spade connectors that fit SNUGLY….touch the leads together to CALIBRATE the ohm meter. The needle should go to ZERO OHMS. If not….turn the adjusting screw until it does.

Connect ONE LEAD to “TERMINAL TWO” and the OTHER LEAD to “TERMINAL THREE”. Yes, you can switch the ohm leads. this will not alter the results.

I went out and bought the CHEAPEST AVOM (Anolog Volt Ohm Meter) I could find. Pep-boys $9.99. Also available at Radio Shack, Auto Zone, etc.

This AVOM has ONE Ohm setting. 1K ohm or ONE KILO OHM. That’s “Zero to 1000 ohm range”.

There are two “INSPECTIONS” to perform to the TPS. We will start with the “SWEEP TEST”. No, you can’t do this test with you high dollar DVOM!!!
What you want to see: NO STALLING of the needle…or a CHANGE IN DIRECTION of the SWEEP Exclamation Shocked

The first test pic………as you can see (no hands in pic) is taken at the IDLE position. Don’t worry what the numbers say, this test is not about numbers.

New TPSs went obsolete! Rolling Eyes Contact Professor Quest
for a BOSCH replacement…that is TWICE the quality! Cool

You can upgrade to a 2 gauge ground cable.


You have the right to remain… Rolling Eyes TROUBLE FREE! Cool

SUPER NOTE THIS: As you LEAVE IDLE SLOWLY…KEEP YOUR EYES ON THE NEEDLE Exclamation That NEEDLE needs to RESPOND with NO *STALLING* of the needle movement ExclamationExclamation

That AREA of the TPS RESISTANCE is HARD WORKED….. Rolling Eyes

Unplug your TPS. With the harness DISCONNECTED to the TPS, Turn it upside down and place it back into the harness holder with “TERMINAL ONE” at the top.

Connect one AVOM lead to “TERMINAL TWO” & the other lead to “TERMINAL THREE”. I used male spade connectors (14 gauge) and pulled the insulation off.

Take a pair off wire cutters and snipe down the spades to make them narrow. The tips of the AVOM leads will slide into the spade openings and give you a GOOD CONTACT but you may need to crimp them slightly. As you can see….

….the more I open the throttle………..the more the POINTER moves left……which means the RESISTANCE is INCREASING.

In other words…..the needle (ALL OF A SUDDEN) just changed the direction of it’s movement! Shocked No, you can’t tell in “still shots” but the POINTER is NOT doing this smoothly. Right now the ECU is going…….WTF? Laughing

The more I open the throttle……….the more the POINTER moves AWAY from the “HIGH RESISTANCE AREA”. That area has more resistance because that is WHERE the car is driven MOST so the CARBON FACE inside the TPS has more wear at this throttle position.

I’m at about 3/4 throttle, now. The TPS is starting to come back to where it should be. But it’s already failed the test.

I’m now at WFO throttle. I could adjust the TPS to go to ZERO resistance at this point. But it won’t do a bit of good. If this TPS was sending this kind of signal to the ECU….the car would hesitate………run like crap……..then take off.

Watch the manual……..the words…..”TPS INSPECTION” page 14-65 and…….”TPS ADJUSTMENT” page 14-32 are two DIFFERENT THINGS.

Yes, you do use a *DVOM* to ADJUST IT’S VOLTAGE! Wink

IMPORTANT TIP: When you make the adapter harness, do not place all the open copper areas the same distance. They could touch each other and SHORT. Space them out.

Now then….once you have a GOOD TPS…….you can ADJUST IT using VOLTS. Open manual to page 14-32, 14-33, 14-34

Make the little harness adapter above. Start the car, let it warm up. Adjust the VOLTAGE at idle to 0.48-0.52 volts. Now……turn it off.
When you open the throttle all the way you should see AROUND 4.5 -5.5 VOLTS.

You might make 4 of those wires……you’ll need them for the ISC adjustment.

You DO NOT WANT…the throttle cable holding-open the butteryfly! Rolling Eyes  At idle, there should be a small-amount of SLACK, on the cable!


below: The ISC adjusting screw is used to CHANGE your idle speed.
Specs are 950rpm + or – 50 RPM.
Once set…re-adjust your TPS to .48v-.52v!!!!!


When you build this test/set harness…spread apart the open copper area so you don’t accidently SHORT CIRCUT. Rolling Eyes

The females are pretty easy to find. I just Dyke the males from a standard male connector. I keep forgetting to order more of the males. You can tie in alligators as well to make life easier. Wink

You can make and adapter to make things easier when having to set your TPS.


Fingers are missing on the RH arm….but wait, where do you suppose they COULD be laying on? Shocked

Btw…a bunch of GREEN CRAP fell out the secound I removed the top. Sorry…no pic cause the wind blew-it away. Embarassed

Note the far right terminal….ETCHED all-ta-hell too.

Also note the VINYL shows EXPOSED COPPER…. Shocked Meaning…it’s NO LONGER SEALED! CONTAMINATION, HUMIDITY is gonna ENTER the TPS!



Another BAD SWEEP TPS….the fingers are there, but those fingers are BURRIED IN CARBON! (sorry bout the focus) But an assistant just HAD to touch the fingers…and the carbon feel-away….put it back together and NOW the SWEEP was GOOD. Rolling Eyes


Try to follow this: Rolling Eyes The TPS has it’s own ground that is supplied by the ECU/ECI. (the computer) The computer get’s it’s ONLY ground right HERE! It is the SMALLEST of those ground wires and that SINGLE ring-eyelet became TWO ring eyeletes in later models…and we have found those ring-eyelets to CRACK IN-HALF! Shocked

Note the letter “E” on that bolt. It means it was platted special for electrical use. On your electrical fan shroud, two more “E”bolts (8mm) are for those two black ground wires at the top of your RADIATOR!!

Bottom line is….a RUSTY, CORRODED bolt can not transfer electrical very well.

Another ‘parts car’, white 85. GREEN COLOR ON COPPER MEANS:…… Rolling Eyes GRAVITY MEANS:……… Rolling Eyes TRASHED NEGATIVE CABLE! It travels down thru the INTERIOR of that cable.

You would BLAME a bad sensor…..or a harness connector (clips-pigtails)
ANYTHING….but just doing a simple CLEANING of those junctions. Rolling Eyes

If a battery cable looses .2 volts..over the length of the cable…it is OFFICIALLY TRASHED! REPLACE IT! Wink

This red Starquest is a parts car. I’ll use it for pics. In 88, Mitsu INCREASED the size of the ground cable. Wink

GROUND # 11. I see this all too often on Starquest. The negative cable end was cut off and a bolt-on end replaced it. However, to make the cable reach the battery….they unbolted the MOST IMPORTANT GROUND IN THE CAR and replaced it with the smaller red wire. One look at the bolt that retains it to the apron says it all. This is one poor ground.