I have 02 L300 3.0 with cylinder1 miss fire.I

I would check for unmetered air getting in. Look for cracked or missing vacuum lines

Potentially serious and costly to repair if left unresolved.
Check out this link for info and repair strategies

Hope this helps

the code refers to the heated oxygen sensor (HO2S) and not the O2 sensor which is a different sensor
It is a generic code and refers ti injector and fuel problems
The misfiring can be from injectors as well as plugs so check for fuel pressure and blocked fuel filter

Have you checked all fuel injectors? Miss fire data is determined by ignition miss. I would also double check that all plug wires are fully seated on plug

Thanks for choosing FixYa. This can relate to a number of things. It could be bad spark plugs, spark wires, coils. It could be a bad fuel filter. It may even be something electrical. Your vehicle has to have the perfect percentage of air, fuel, and fire to run correctly. If it has been awhile since you did a tune up, get one. If the check engine light is on, check for codes. It could even be a vacuum leak, so check your vacuum hoses and air filter. Since it is a bad miss, it is probably not in the hoses or filter, but bad air can cause it. Could be a bad fuel injectors.

Misfires are either fuel/air mixture or spark.

If you've got the spark, then start looking at the fuel/air mixture. Check the plugs to ensure that they are in good shape (no cracks, not discolored, properly gapped).

Double check the plug wires and firing order... if everything checks out, then you could be having a vacuum problem such as an intake gasket leak.

Good luck!

First off you want to make sure that you have the correct firing order down. When you rearranged the spark plug wires you might have made the firing order off and that could cause the misfire to get worse. the things that you should do to isolate the problem is to perform compression tests, fuel injectors, and also check the entire ignition system

Check for low weak compression, or an intake leak on that cylinder. Make sure the plug is getting spark, and that the injector is pulsing.

ASE Mechanic:
inspect everything from spark plugs, wires, fuel filter, air filter and maf sensor, mostly likely your due for a major tune- up. be carful the middle spark plug on the drivers side of the engine is very tricky and even a skilled technician can have problems.

Just a few things to check. Take off the fuel filter and make sure there is no water in it. If you have put in different spark plugs than AC Delco, then change them to AC Delco. If you haven't looked at the plugs or the fuel filter, then it is way past time to replace the filter and new AC Delco spark plugs only. These places that insist that you use Bosch plugs or split fire plugs don't know ****. The Delco plugs are made especially for your engine and will out last those cheap non-working Bosch plugs.
If the fuel filter and plugs don't fix it, make sure your air filter intake isn't stopped up with a bird's nest. Happens a lot. If it still misses after new plugs, you may have a fuel injector sticking.
The bad smoke is the gas-thinned oil passing the rings and unburnt fuel smoke. The missing really bad is most likely fuel soaked spark plugs. Make sure you change the oil while changing the plugs or you will have a redo. Let us know if any of this helps. Dale