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Do it yourself information page
This page is for the small tips and tricks that will make for installing and maintaining your TPI more enjoyable.
Setting Minimum Air Idle Speed Serpentine Belt Adjustment Check TPI Manifold Tightening Sequence
Setting TPS idle voltage Fuel Filter information
TPS installation tip Fuel Rail and Components
Idle Air Control Motor Cold Start Injector and Parts
Setting the TPS idle voltage (after new sensor installation and verifying the idle voltage is set correctly). Before you can set the TPS idle voltage you must insure the minimum air idle is set.
NOTE: You must use a high impedance digital volt-ohm meter (typically 10megohms per volt) for this adjustment. Do not use a analog meter as they are normally round 10-20K ohms per volt and will induce a load into the voltage being tested and give a false output reading. And they are not accurate enough for fuel injection work.
Be sure your battery is fully charged, if you have a charging problem, you will need to correct this before you continue.
First be sure that there is no deposits behind the throttle plates and in the IAC air bypass passage ways. This deposit or "coking" is a mixture of soot and oil that is part of the combustion process. In older engines, a significant amount is oil. If this deposit is enough, it will effectively choke off the air flow to the IAC, causing hesitation and stalling. The best way to clean this is to remove the throttle body from the intake, and using a can of brake cleaner, rags and cotton swabs. Clean in front and behind the throttle plates, remove the IAC and clean the pintle end and the passages on the throttle body. Once this clean, reinstall throttle body. To adjust the minimum air, you must first install a jumper on terminals "A" and "B" on the ALDL. Do this with the key on, engine off. Wait about 30 seconds or so. This will allow the IAC motor to fully extend and close off the air bypass. Without turning off the key, pull the connector off the IAC motor. Start the engine, and let it warm up fully before adjusting. Then it will be at the minimum speed set up. Set the appropriate idle speed specified for your application found in your automotive manual, typically around 450 rpm for the TPI cars. Use the correct torx bit end tool to move he idle screw in or out to achieve the proper minimum air speed. Now you can set the tps to the correct voltage.
Adjusting the idle speed for minimum air is down by turning the idle stop screw clockwise to increase idle speed, counter-clockwise to decrease the speed. The tool is a torx bit end.
To
adjust the TPS to its proper voltage, back probe the center (blue) wire with a
small pin or paper clip until it bottoms out on the terminal inside the connector.
To check for continuity, use a meter or self power continuity checker to see if
you have a continuity between the probe wire and the center
terminal.
Install
the tps connector back on the sensor, and hook the positive (red)
lead of your digital meter to the probe wire. For meter leads that are
point ends instead of clip ends, you will have to purchase or fabricate jumper
clips to connect your meter. The negative (black)
lead will have to be connected to a good grounded point on the vehicle, such as
the negative battery cable terminal.
Set
your meter up on the lowest scale, which will need to be at least on the hundredths
(two placed right of the decimal point) scale.
Turn
the ignition key to the "on" position, but DO NOT start the vehicle.
If your meter is not showing any voltage, verify it is working by testing your
battery voltage, if okay, check you probe wire on the tps connector and make
sure it is making contact.
Loosen
the screws on the sensor just enough to move the sensor up and down, you should
be able to verify this by watching the voltage change on the meter.
Move
the sensor to get around .45 to .55V on your meter. Tighten the screws one at a
time. You will notice as you tighten one screw, the voltage may go up or down
from the desired set point, when this starts to happen, tighten the opposite
screw to oppose the voltage drift and continue back and forth until the voltage
is in the desired range. This make take a couple of times to get the "hang'
of it. DO NOT over tighten the sensor screws!
The
final adjustment should result in a stable tps voltage.
Be sure the tang of the sensor's pickup lever is in the position shown, lining up with the tang on the throttle boys actuator lever. Do not over tighten the mounting bolts.
When replacing the IAC motor, or reinstalling the old one, be sure that the measurement from the end of the pintle to the IAC motor seat does not exceed 1 1/8" (see Dim. "A" in diagram). Do not install the gasket before measuring and adjustment. If it is longer than that grasp the IAC in your hand with the pintle facing up and with your thumb, rock the pintle back and forth gently while pushing down. If it is jammed and wont move at all, consider replacing it.
Serpentine Belt Adjustment Check
There were two styles of serpentine belt set ups used. The earlier years had a idler pulley similar to the one on the left. The most common, however, is pictured on the right. As the belt stretches over time, the tensioner mark will move clockwise t the right. The right hand picture shows when a brand new belt is installed, the upper mark (arrow) on the stationary side will be aligned with the mark on the pivot side. There is a series of three arrows , then a wide space and an arrow to the far left of the pivot end, which indicated the point the belt needs to be changed.
Also replace the belt if ribbing is coming apart in chucks. Small hair line cracks that run opposing the ribs are okay, large cracks with pieces of the belt missing necessitates replacement.
The fuel filter should be changed at the maximum of two years, sooner in areas where fuel quality may be questionable. Also check the o-rings (red arrows) when replacing the filter, if they are brittle, or show signs of gouging, tearing or stretching, they must be replaced or a dangerous fuel leak will occur.
Fuel Rail and Components Corvette fuel rail shown, F-body fuel intake and return lines on drivers side.
TPI Manifold Tightening Sequence
Replacing Broken Sensor Connectors
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