Hi guys,

I got P0300 tonight and dont' know what to look for first.

there are so many things to check. What is the most common cause for P0300 for 4runner?


Any suggestions? comments?



Thanks

Symptoms may include:
the engine may be harder to start
the engine may stumble / stumble, and/or hesitate
other symptoms may also be present
Causes
A code P0300 may mean that one or more of the following has happened:

Faulty spark plugs or wires
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector(s)
Burned exhaust valve
Faulty catalytic converter(s)
Stuck/blocked EGR valve / passages
Faulty camshaft position sensor
Defective computer
Possible Solutions
If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.

If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.

Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.

yea, i posted similar links as you in his other thread on the issue, i guess he's looking for a more definitive answer or like he said "the most common cause of it in the 4r", but the answer to his P0300 may not be that easy. if it was a P0302 or similar, you would at least know what cylinder to start with, my suggestion to the op would be to start at the top of the list & do what you think you can with the tools/equipment you have & if nothing works, bite the bullet & take it to a shop.

Check the plugs first. Go from there.

LOL~thanks man. The other guy just copy and past. ~_~

I concur. if I have cylinder number, the problem would be a lot easier to find.
it happens after I change spark plugs. maybe it doesn't like Denso 5344 plugs.

I replaced them withDenso 5344 Spark Plug. WRONG PLUGS?? OR WHAT? I DID VERIFIED THE GAP .43

even tho a check says you can use the 5344 which is stock # for IKH20, i thought i read somewhere that someone else said they had a problem with them, eitherway, this is whats listed for your 04 v6 on denso's site, IKH20, IK20HR-U11, PKH20TT, SK20HR11. what were your old plugs? half NGK/halfDENSO? not iridium right? i wonder if you cleaned them up a bit & temporarily reinstalled em would you still have the misfire? since the new plugs are different than the old ones, something you might try first is disconnect the - batt. term to reset the computor, then reconnect after 5 min. & see if the same code pops back up

ive been getting the same code p0300. exhaust smells bad and i have a stumble on heavy acceleration. thats also when the light comes on, it flashes first then comes on steady.

bad cat?

My 2002 4Runner is giving the same P0300 code. I have replaced spark plugs, spark plug wires, performed throttle plate & fuel system cleaning, replaced all engine coils, replaced fuel filter, replaced fuel air ratio sensor and still get the dreaded P0300 code. I replaced the catalytic converter in 2019. I am at a complete loss now. Any advice would be appreciated. Thanks.

@MiketheVike any luck figuring it out? i'm in a similar situation