After engine has warmed three cylinders are not getting fire/voltage

Hi,

Did this happen all at once? What I would suggest is to check the coils to confirm they are good. This should be done when the spark is lost. Also, you could try to switch the three bad coils with the three that are working to see if the misfires change cylinders. If they do, the coils are bad. If you have already identified diagnostic trouble codes, let me know what they are.

Here are the diagnostics for checking the coils. The attached pics below correlate with the directions.

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2003 Toyota Truck Highlander 4WD V6-3.0L (1MZ-FE)
Component Tests and General Diagnostics
Vehicle Powertrain Management Ignition System Ignition Coil Testing and Inspection Component Tests and General Diagnostics
COMPONENT TESTS AND GENERAL DIAGNOSTICS
INSPECT IGNITION COIL (WITH IGNITER) AND SPARK TEST

a. Confirm DTC.

NOTE: If DTC is indicated, carry out troubleshooting in accordance with the procedure on the following DTC.

B. Check that the spark occurs.
1. Remove the intake air surge tank.
2. Remove the ignition coils (with igniter).
3. Using a 16 mm (0.63 in.) Plug wrench, remove the all spark plugs.
4. Install the spark plugs to each ignition coils (with igniter), and connect the ignition coil connectors.
5. Disconnect the all injector connectors.
6. Ground the spark plugs.
7. Check if spark occurs while engine is being cranked.

NOTE:
- Be sure to ground the spark plug when checking.
- Replace the ignition coil when it is given an impact.
- Do not crank the engine for more than 2 seconds.
If the spark does not occur, do the test as follow.

C. Using a 16 mm (0.63 in.) Plug wrench, install the spark plugs.

Torque: 18 N.M (184 kgf. Cm, 13 ft. Lbf)

d. Install the ignition coil with igniter.

Torque: 8.0 N.M (82 kgf. Cm, 71 in. Lbf)

Step 1 - 2

See pic 1

Step 3

See pic 2

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Try this and let me know what you find or if you have other questions.

Take care and God Bless,

Joe