Code P0304 misfire help

[mgcorreia]

Hi, I have a 1997 Toyota 4 Runner, 4 cylinder, manual transmission, with 207k miles.

About a month ago I got a code P0304 (misfire cylinder 4). I was experiencing rough idles, poor performance when accelerating, and my shifter knob was shaking about.

So I replaced the spark plugs and the wire set. Problem solved.... That was until a month later when I got up this morning. My car had a bad case of the Monday's. Cylinder 4 was misfiring all the way to work with all the same symptoms and the same code. When I got home I pulled the spark plug out of cylinder 4. It looked a little burnt around the tip. The boot looked good. Here is a pic of the plug. What do you think I should try next?

Also, I don't know if they're related, but when cruising on the freeway I occasionally get code p0420... catalyst system efficiency below threshold. I recently had to get a smog certificate to register the car and they said I passed with flying colors for California standards.

Thanks to everyone who reads this!

 

[Drcoffee]

There is a good chance its your fuel injector. The good news is you can buy a reman injector for $30. The bad news is it is on the drivers side. Plan to spend big money to pay a shop or a good afternoon taking off the intake. If you do it, plan to fix the leaking valve cover gaskets while you are in that far.

 

[chadsy]

It looks like you're not using the dual electrode spark plugs.

I would consider using the duals when you redo everything.

 

[mgcorreia]

Yeah I went for the single electrode NGK plugs. The guy at Autozone said because my car had 200k miles on it, a spark plug with more than one electrode on would be too much stress on the engine and could damage it. He also said if the new wires and plugs don't fix it , I might consider changing the distributor cap. ...

 

[mgcorreia]

how about a fuel injector cleaner instead? Guy at autozone said a distributor cap replacement may be in order if the new plugs and wires didn't fix it.

 

[PitbullRescuer]

Yeah I went for the single electrode NGK plugs. The guy at Autozone said because my car had 200k miles on it, a spark plug with more than one electrode on would be too much stress on the engine and could damage it. He also said if the new wires and plugs don't fix it , I might consider changing the distributor cap. ...

Tell the guy at Autozone that the guy in Japan that engineered the truck and decided it needed dual ground plugs may know quite a bit more than he does.

 

[Diesel_Dog]

Yeah I went for the single electrode NGK plugs. The guy at Autozone said because my car had 200k miles on it, a spark plug with more than one electrode on would be too much stress on the engine and could damage it. He also said if the new wires and plugs don't fix it , I might consider changing the distributor cap. ...

There is good reason why you want the duals, do a search but I believe that the plugs fire twice in a cycle. Our trucks also don't have a distributor rather they have coil packs. Make sure that you get a good seal when clicking in the plugs and use some dielectric grease.

To help trouble shoot if the problem still persists after the above, you could try swapping the 'bad' coil with a good one. If the problem follows the coil you know that is what you need to replace.

 

[mgcorreia]

good point, bummed I wasted money on these single electrode crap sparkplugs. Plus these are the exact same plugs that were originally in the car when the problem first occurred. Would you use NGK or another brand?

 

[kball]

This is a 4cyl. Don't the 4 cyl engines all have their own wires?? No waste spark system right?

 

[mgcorreia]

I put some more anti seize on that sparkplug, put it back, and reset the CEL light. Drove to work today, no problems at all. Very weird....

 

[wannabeflyingkites]

p0304 cylinder 4 misfire

got rough idle, all the bells & whistles going off. jumped straight in. change plugs, coil packs and all. ran worse after $200 investment. went back to 4's coil pack, lucky me bought an xtra one. swapped out coil, but on the connector I put some dielectric grease. problem gone
06 4runner 4.0l 205k 2nd owner. I think that the miles & time messed up electrical connection. I will be putting that sh!! on everything!!!
wannabeflyingkites

 

[Bad Luck]

got rough idle, all the bells & whistles going off. jumped straight in. change plugs, coil packs and all. ran worse after $200 investment. went back to 4's coil pack, lucky me bought an xtra one. swapped out coil, but on the connector I put some dielectric grease. problem gone
06 4runner 4.0l 205k 2nd owner. I think that the miles & time messed up electrical connection. I will be putting that sh!! on everything!!!
wannabeflyingkites

You are in the 3rd gen section (1996-2002). Try looking in the 4th gen section: https://www.toyota-4runner.org/4th-gen-t4rs/ or using this 4th gen specific google search: https://www.google.com/search?q=site%3Ahttps%3A%2F%2Fwww.toyota-4runner.org%2F4th-gen-t4rs%2F&newwindow=1&rlz=1C1QJDB_enUS784US793&sxsrf=AOaemvIDTWHKZuxWO3sN5fsPBY2Yx-2ZtQ%3A1632233887138&ei=n-lJYd_kB4a7qtsPoIiuwAs&oq=site%3Ahttps%3A%2F%2Fwww.toyota-4runner.org%2F4th-gen-t4rs%2F&gs_lcp=Cgdnd3Mtd2l6EANKBAhBGAFQ0BxY0BxglitoAXAAeACAATyIATySAQExmAEAoAECoAEBwAEB&sclient=gws-wiz&ved=0ahUKEwifsKGIoZDzAhWGnWoFHSCEC7gQ4dUDCA4&uact=5