Tune Ups

This section will cover basic tune up information ranging correctly setting your timing to idle speed adjustment and such. I will try to divide the information by years.


1985 to 1991

Setting the correct idle speed on a tpi motor

I do not remember where I got this from but it covers the procedure perfectly.

Jumper pins a & b on the diagnostic connector under the dash. Unplug timing connector under hood by the ecm.

Turn ignition on but do not start car. Wait 30 – 40 seconds. Unplug IAC connector.

Unjumper pins A&b and start car.
Keep it running with the gas and adjust idle to about 450 to 550 rpm.

Turn car off.

Plug IAC back in plug the timing connector back up and start car again.
It probably won’t run right the first time you restart it so turn it off and restart one more time.

If your factory tach is off you will have a hard time getting it set right.


You set the minimum air adjustment using the little set screw on the TB,
this is how you set to say 500-550 RPM. Once set do not touch the screw again (unless you go through the whole proceedure).
I was able to set mine with the timing wire connected, if you have a hard time getting it to idle
you can disconnect the wire

There are two electrical components on the TB that you will be working with:
The TPS and the Idle Air Control Valve (IAC). Make sure that the connectors for these two components are
easily accessible and that you can easily disconnect the IAC. You will also be playing with the
diagnostic connector under the dash. Remove the cover (if it’s still in place).
Bend your paper clip into a “u” shape. You will be playing with the two top right hand terminals (“A” to “B”)
in the connector.

1. First step is to set the minimum idle speed. If nobody has messed with this on your car before,
the set screw will be covered by a pressed-in plug. It’s located on the driver’s side of the TB.
Remove this plug if it’s there.

2. With the IAC connected and the ignition “OFF,” stick the paper clip into the diagnostic connector
from “A” to “B.” This grounds the diagnostic lead.

3. Turn the ignition to the “ON” position without starting the engine. Wait 30 seconds.

4. Now, with the ignition still in the “ON” position, disconnect the IAC connector at the IAC.

5. Remove the paper clip from the diagnostic connector.

6. Start the engine and allow it to reach normal operation temperature. The idle speed will probably be
really low, and you may have to coax the engine a bit with the gas pedal to keep it running for a while.

7. If your car is an automatic, set the parking brake and put the transmission in “DRIVE.”
If your car is a manual, leave it in neutral.

8. Adjust the idle speed screw to obtain 400 rpm in drive or 450 in neutral.

9. Shut off the engine and reconnect the IAC.

That’s it for idle speed. Now on to the TPS.

There are 3 wires stacked vertically on the TPS. You will need to be able to measure the voltage
between the two top wires. You can either buy a special harness connector that breaks these wires
out (from Min America), or gently pierce the insulation of the wires with the pointy prongs on your
volt meter. You can also stick a paper clip into each of the two top locations of the connector and
clamp onto the paper clips to measure the voltage. Whatever is easiest for you.

1. Turn the ignition to the “ON” position without starting the engine.

2. Loosen the TPS Torx adjustment screws.

3. Set your volt meter to the low scale DC volt setting that will accurately read less than 1 volt.

4. Measure the voltage between the two top TPS wires.

5. Adjust the TPS by rotating its position until you get a reading of .54 volts.

6. Tighten the Torx screws and recheck the voltage. Readjust if necessary to make sure voltage is
right at .54

7. Turn the ignition “OFF.”


The Nest – All things crowz….