Question:How do you check or adjust ignition timing on
an engine with a distributorless ignition system?
Answer:You can't do either on many engines, but checks
and adjustments are still possible on others.
On some distributorless ignition systems, timing is fixed
and cannot be adjusted. Nor are any timing marks provided on
the crankshaft pulley for reference checks. If there are any
problems (like a bad crankshaft position sensor), the onboard
computer is supposed to pick it up and illuminate the Check Engine
light. Otherwise, you have to assume everything is fine.
On other engines without distributors, the crankshaft position
sensor and/or cam position sensor allows a certain amount of adjustment.
Loosening and rotating the sensor's position has the same effect
on advancing and retarding timing as rotating a distributor.
Timing marks on the crankshaft pulley are usually provided so
a conventional timing light can be used to check timing.
To check timing, attach a timing light to the number one spark
plug wire. Use the light to illuminate the timing marks on the
crankshaft pulley as the engine idles. Refer to the engine emissions
decal or a shop manual for the timing specs.
To adjust timing, loosen the crankshaft or camshaft sensor.
Then rotate the sensor's position in the same direction as the
crankshaft or camshaft turns to retard timing, or in the opposite
direction to advance timing.
On some engines timing can also be checked electronically
through the computer system itself by plugging a "scan tool"
into the computer's diagnostic connector.
