Testing A Pwm Iac Valve; Checking Rpm; Setting Cranking Timing - amp e MS3Pro ULTIMATE User Manual

6.1 Getting started
– Both coils are wired backwards for the way your tune is configured. With the current firmware, you can
simply change the homing direction in the software. 1.2.4 and earlier code does not allow this. If you
encounter this problem on older firmware, you can reverse the wiring. Switch wires 1A for 1B, and 2A
for 2B.
• Problem: Valve does not move at all on initial power up.
– One possibility is incorrect wiring. Make sure 1A and 1B are on one coil, and 2A and 2B are on the
opposite coil.
– The other usual problem is the time step size is set too small. Try increasing it and see if the valve
moves.
• Problem: Idle speed is not consistent from one start to another at the same temperature.
– Usually, this is caused by the homing steps being set too low. Increase this value until the valve retracts
fully.
– If the valve sometimes retracts fully, but not always, this may mean the steps are small enough that they
do not always successfully move the motor. Try increasing the time step size.
• Problem: The valve retracts normally, but then appears to stop working at some point during operation.
– Try increasing the time step size and/or minimum number of steps to move. Some older valves can
have problems with stiction. Increasing the time step size will send a longer pulse, while increasing the
minimum number of steps to move will send more pulses that can un-stick a stubborn valve.
• Problem: Idle speed hunts while the number of steps displayed is constant.
– It's easy to assume the IAC valve is responsible here. After all, it's supposed to control the idle speed,
and the idle speed is behaving wrong. However, this is likely to be an issue with the ignition timing or
fueling instead.
Testing a PWM IAC valve PWM valves do not need a homing routine, as the PWM output directly controls
their position. As noted above, be sure your valve has power when testing. The "PWM idle duty" box allows entry
of 0-100% duty output. This could be used to confirm operation of the valve as well as determining what duty cycle
gives what RPM with the engine running.

6.1.2 Checking RPM

Next, we'll disconnect the injectors and check to be sure the RPM input is working and your timing is correct. Pull
the fuses to the injectors, or disconnect the connectors on the injectors, and crank the engine. With TunerStudio
connected and running, turn the key on and crank the engine. If all is well you see "Synced" and a stable engine
speed (rpm) number. If the pattern is noisy, incorrect or missing you might see "Synced" then "Not-synced" and/or
rpm jumping up and down. The tooth logger (see section 8.3) should also be used to confirm that the pattern is
stable if you do not have a steady RPM. Keep working on the crank/cam sensor inputs until you have stable rpm
with no loss of sync.
While cranking, take a look at the fuel load (MAP sensor) reading in TunerStudio, if you are running speed
density. You should expect to see it drop slightly as the engine pulls some vacuum. If it stays stuck on atmospheric
pressure (near 100 kPa) then your map hose might be connected incorrectly.

6.1.3 Setting cranking timing

Having confirmed that the coils work as expected and with the fuel pump still disconnected, hook up a timing light
to plug lead #1. Yes, this is really needed - correct timing is very important. If you are running wasted spark you
need to ensure your strobe is compatible. "Dumb" timing lights are fine; some dial-back lights can be awkward.
Use a "2-stroke" setting for wasted-spark or wasted-COP if you have a dial-back light. With a coil-on-plug pencil
type coil you will need to remove the coil from the engine and install a short length of regular spark plug wire from
AMP EFI MS3ProUltimate manual version 1.203, firmware 1.5.0, 5/23/2017
6 TUNING THE MS3PRO
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