dreaded P300-P304 code.

[T4Rscott]

Hi all,

It's been awhile since my last post, apologies, new job keeps me busy.

I got the dreaded P300- P304 combination recently. The 4R starts fine when cold, but upon starting after coming out of the store, it starts to chug almost, then goes back to normal in couple of miles. I did the plugs last fall, wires were 3 years ago. could this be and injector? I plan on doing the coil move procedure to see if it follows. If it is an injector, should I replace the 1 or do all 6? How often do the blue NGK wires need replacing? I remember a site where you can send in injectors and get the rebuilt. Does that site still exist?

Thanks,

Scott

 

[jgue467]

Pull the plugs

and have a look. what color are they? dry/wet? That's the proof of what ya got going on. You have choices from there, either attack it one component at a time (can be a pita that way) or just bite the bullet and give it a complete tuneup, you'll be happier in the long run...do you run some kind of fuel treatment (e.g. seafoam, startron, etc.)?

 

[Gio6501]

Slight shake at start up only

saw you had the same issues I'm having with my 04 4Runner. After replacing my plugs coil in cylinder 4 due to the code.
My mechanic is suggesting to run the truck for a week or so and check if the coolant level drops because my injectors are good so I'm afraid it may be the HG. Toyota also said this is a common problem for those models . I have the v6 sport edition as well. Did you have the HG replaced and if so did this resolve the problem? Any info would be greatly appreciated! I have 116k miles on the truck which isn't much for a Toyota . The miss only is at the first 15 or so seconds of start up , then it runs smooth . So frustrating . Ty

 

[The Count]

saw you had the same issues I'm having with my 04 4Runner. After replacing my plugs coil in cylinder 4 due to the code.
My mechanic is suggesting to run the truck for a week or so and check if the coolant level drops because my injectors are good so I'm afraid it may be the HG. Toyota also said this is a common problem for those models . I have the v6 sport edition as well. Did you have the HG replaced and if so did this resolve the problem? Any info would be greatly appreciated! I have 116k miles on the truck which isn't much for a Toyota . The miss only is at the first 15 or so seconds of start up , then it runs smooth . So frustrating . Ty

The problem the OP is having is NOT the same as your 4th gen, which has a different engine.

 

[The Count]

and have a look. what color are they? dry/wet? That's the proof of what ya got going on. You have choices from there, either attack it one component at a time (can be a pita that way) or just bite the bullet and give it a complete tuneup, you'll be happier in the long run...do you run some kind of fuel treatment (e.g. seafoam, startron, etc.)?

"Reading" spark plugs is far from an exact science. The only thing, other than physical damage or oil burning, that plug reading can typically tell you is if the cylinder was running extremely lean or extremely rich when the engine was shut off.

It would be more useful to pull the plug and check the insulator for cracks or carbon tracks. Also check the spark plug boot over very carefully for burnt holes in it. Check the spark plug wire for burn marks, rubbed spots or cracks. Then ohm the #4 wire and compare that reading to the reading for one of the other two wires, it should be very close if the wire is good. Ohm the coil pack and compare to one of the other coils.

It could be an injector but is more likely to be an ignition misfire, since it actually picked it up and set a code. But if it were a bad injector, replacing 1 or all of them is a matter of available $$$ and personal preference.