Troubleshooting Code P0305

[jredsock]

Hi, I'm new to this website. My 1999 Lexus RX300 that I purchased 4 months
ago had run great until today.I was driving along, stopped at a red light and all of a sudden,bang it started idling rough and felt like it was going to die right there.Well I nursed it home and went to my friend who has a code scanner. We hooked it up and got a P0305 code which is a misfire on cylinder #5. Does anyone have an idea as to what the problem might be. My friend thinks it's the coil. Can a coil be good and then in a flash,fail? All help would be appreciated. Thanx

[Brian R.]

Welcome to the AF!
First thing to do is pull the plug and see if it's fouled or if it's the wrong plug type for your vehicle. That is the easiest solution, just replace the plug (should be Denso PK20TR11 or NGK BKR6EKPB-11).

If everything is beautiful in spark plug land, while the plug is out, ground the plug and see if you get a hot blue spark when you crank the engine. If so, then it's probably your injector for that cylinder. Check the resistance of the injector (should be 13.8 ohms). Replace the injector if bad. If you have spark and resistance is ok, injector may be plugged. Clean it or replace it. You can get it cleaned or tested.

If no spark, check the connection of the ignition coil and ignitor. Check the resistance of the wires that feed that cylinder. They should all be less than 16 kohms. Replace if bad.

If everything is good so far, check that you are getting battery voltage at the (+) terminal of the coil. If no voltage, check wiring between the ignition switch to the oils and ignitor.

Check the resistance of the coil. Cold, resistance of primary should be 0.70 - 0.94 ohms and secondary should be 10.8 - 14.9 kohms. Hot, primary should be 0.85 - 1.10 ohms and secondary should be 13.1 - 17.5 kohms. Replace the coil if bad.

Check the resistance of the camshaft position sensor. Should be 835-1400 ohms cold or 1060 - 1645 ohms hot.

Check the resistance of the crankshaft position sensor. Should be 1630 - 2740 ohms cold or 2065 - 3225 ohms hot.

Replace these if bad.

If nothing is bad, replace the coil. It is most likely bad even if the resistances are ok.

[ModifiedMCS]

An old thread. but things to check for: I think its coil on plug. swap cylinder 5 coil with another cyl. Maybe cylinder 2 coil and see it if problem migrate with that coil. if not. then it could be a bad cyl. 5 fuel injector. or maybe damage to fuel injector wiring or coil on plug wiring due to rat damage.