2ManyLexus

I have a 2004 LS430 with 91K miles. After 7 weeks sitting in the garage, not surprisingly, I had to jump start it. However, shortly afterward (coincidental or not), "Engine" & "VSC off" dummy lights illuminated. Also noticed engine was running rough. I thought these problems may have been because I jump started it in the garage (on an angled surface). Moved car to level surface, disconnected the battery temporarily & then restarted it. Both lights reappeared after a few minutes and the idle became rough. Drove the car to Autozone to obtain fault codes. Notice idle was ok initially (for a couple of minutes) then rough. Car engine diagnostics showed P0303, Cylinder 3 misfire error code. Removed engine shroud & attempted to isolate cause. Swapped coils and ruled out Cylinder 3 misfire is caused by a faulty directignitioncoil. I have replaced the spark plug in Cylinder 3, but the engine appears to be misfiring with the new plug, and the "Engine" & "VSC Off" light is still on. I believe the remaining potential causes would be the ignition coil wiring or bad cylinder compression. I visually inspected the wiring and nothing jumped out at me as a problem. Although being Cylinder #3, the wiring from the coil routes into a larger bundle connection. Does anyone have instructions on how to troubleshoot the ignition coil wiring? TIA.

Aus430

If it is definitely not a coil or spark plug fault, then it could only be ignition wiring or fuel/air related

then you could try unclipping and reclipping the electrical connector to the fuel injector.

Other easy checks are a close look at the vacuum hoses which can get old and start leaking air especially the pcv and purge solenoid lines.

however for a better diagnosis, do have access to an obd reader or preferably a techstream cable?

A techstream cable will help reset the vsc. As well as run more indepth checks such as the vvt solenoids that have been known to throw missfire codes.

Bsavage

If you have a multimeter you can check the ohms on the injector and on the connector check for power if that turns out to be good than plug everything back together and use a car stethoscope to listen if that injector is pulsing or not hope that helps you out a bit
Be very careful when removing wiring connectors in the engine bay their all fragile and prone to brake

StanVanDam

If you have ruled out ignition coil and spark plug, the next item I would check is the ignition coil wiring. Disconnect the injector connectors to prevent the engine from starting, then install the spark plug to the ignition coil, place the spark plug on the cylinder head cover to ground it, then crank the engine for 2 seconds and check for spark. If there is no spark, the wiring on that ignition coil is likely dead. You could also buy a spark plug tester to eliminate the spark plug from the test and to test purely the ignition wiring and ECM.

If you get proper spark, that means wiring and ECM is likely good, then you should check the wiring on the fuel injector connector. With the connector pins facing you with the clip on top, pin 1 is on the left and pin 2 is on the right. Turn ignition switch ON, voltage on pin1 to ground should be 11-14V, and resistance on pin2 to ground should be 10 kOhms or higher. Also check resistance of the injector itself, should be 13.4 to 14.2 Ohms at 20C (68F), if not, install a new fuel injector.

If you want to test your fuel injector, you need to remove the injector, attach the SSTs that reroute the fuel line (09268-41047, 09268-41110, 09268-41300), turn the ignition ON (engine OFF) to get fuel pump pressure, and then apply battery voltage to the injector for 15 seconds and measure the fuel volume in a graduated cylinder. The spec is 60 to 73 cubic centimetres (3.7-4.5 cubic inches) per 15 seconds, and after the voltage has been removed, the injector should leak 1 drop or less per 27 minutes.

You could also plug in Techstream and check the freeze frame data at the time of misfire to see if anything stands out.

2ManyLexus

My P0303 cylinder misfire was due to a faulty fuel injector which I had replaced. Tx.