•
If the engine backfires through the throttle, check that “mechanical timing” has not been added or
subtracted with an improper trigger wheel installation.
N.1. Idling Problems
Sections B.3,
B.6 and B.8
should be consulted to determine problems with idling that are tuning-related
before any troubleshooting is undertaken.
N.1.a. Air-Related Idling Problems
•
If using an IAC motor, and the engine is surging at idle, turn the IAC control OFF.
o
If the engine idles nicely, it is likely an IAC tuning problem.
o
If the engine still surges, it is likely an air-fuel mixture problem.
•
If using an IAC motor and the engine runs rough at idle, it is likely an air-fuel mixture problem.
•
If the IAC motor does not seem to be functioning at all, check the TPS closed throttle voltage. This
value must be ABOVE the actual TPS reading at closed throttle in order for the IAC motor to be
engaged.
•
If the engine idles too high, either the IAC motor is not functioning, the RPM value set in the
calibration file is too high, or the throttle plate is opened too far.
•
To check for proper IAC functioning, the pintle should retract fully when the ignition key is first
turned on, if using a 4-wire IAC motor. The motor should then move out by the specified amount in
the IAC motor settings.
N.1.b. Fuel-Related Idling Problems
•
Check for stuck injectors and fuel pressure problems if the idling characteristics cannot be improved
through tuning (see
Section M.1.b
on Fuel Related Starting Problems to see if the fuel injectors are
functioning properly).
•
If the engine is blowing black smoke out the exhaust during idling, the mixture is too rich.
Decrease the IOT, or decrease the VE Table values at the problem area.
•
If the engine misfires at idle, the mixture is probably too lean. Increase the IOT, or increase the VE
Table values at the problem area.
N.1.c. Spark-Related Idling Problems
•
Check for wiring problems before attempting to correct an idling problem. If the plug wires are run
correctly, and the DFUs are powered correctly, check the ignition advance table.
•
Engines typically need at least 10
o
of timing to idle smoothly. Check the Timing Advance Table at
the idle MAP/RPM points.
•
Check the trigger wheel installation to make sure that “mechanical” timing has not been
(unknowingly) added or subtracted.
O.1. Low-, Medium-, and High-Load Problems
O.1.a. Air-Related Load Problems
To function properly, the only air-related load problems arise from improperly sized throttles.
Make sure that a throttle can flow enough air for an engine. Stock throttles on heavily modified engines
will typically cause upper-rpm performance problems.
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TECgt Manual Version 2.0
- Page 113 -
©2008 Electromotive, Inc.
