Hi Terry, my name is John I will do my best to assist you.
Misfiring can be due to several ignition system faults.
- Crankshaft, or Camshaft position sensor.
- Ignition module/engine control computer.
- Ignition coil/wire.
- Fouled spark plugs.
If the spark plugs have not been replaced in the last 30K miles, this is where I would start, it is the simplest and cheapest of the possibilities. Also make sure that the wiring connectors that plug into the ignition coils (on top of each spark plug) are positively connected.
Your engine is equipped with a coil-on-plug setup. To replace the spark plugs you will have to remove the single bolt that holds each of the coil/wire assemblies, and then carefully twist the coil/wire assembly back and forth while pulling up on it. Then you will need a 5/8" spark plug socket, ratchet, and extension to remove the spark plugs. Make sure that the spark plugs are
gapped to .043, if you don't have a
gapping gauge you can get one from an auto parts store.
If replacing the spark plugs does not resolve the misfire then the next most likely culprit is one or more of the coil/wire assemblies. I don't have access to the exact specifications for testing the coil/wire assemblies for your Lexus, but I will try to locate this information.
The next in order of
likely-hood is the camshaft position sensors. Your Lexus should have 2 one attached to one end of each cylinder head. I will attempt to locate the testing specs for these as well.
Lastly the ignition module/engine control computer. To determine if there is a problem here you will unfortunately have to take the car to qualified service center.
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