CEL - P0304 Code

[ieatfish]

I had a shudder the other day and this code popped up. P0304: Misfire Detected → Cylinder 4

After that, didn't notice any difference and cleared the code to see if it would come back. Just came back yesterday but again, don't really feel anything.

Any issues driving on this until I can get it checked out? Also, anyone had this before? I haven't seen any smoke in my exhaust so not sure if it is a constant thing or just a hiccup.

 

[Drcoffee]

P0304 is a generic misfire code on cyl #4. Trouble shoot it. Swap coil packs 2 & 4 and see if the code goes to p0302. That rules out the igniter. Then swap plugs 2 & 4. Same goal. If it comes back as p0304 and its not electrical, then look at fuel injectors. Thats less easy because you need to remove the intake. Even numbered cyl are on the drivers side

 

[ieatfish]

P0304 is a generic misfire code on cyl #4. Trouble shoot it. Swap coil packs 2 & 4 and see if the code goes to p0302. That rules out the igniter. Then swap plugs 2 & 4. Same goal. If it comes back as p0304 and its not electrical, then look at fuel injectors. Thats less easy because you need to remove the intake. Even numbered cyl are on the drivers side

Awesome, that's a good plan. Do you know how long (miles driven or what) it takes for a code to reappear once cleared?

 

[Drcoffee]

Hard to say. I had a bad fuel injector once and it took about 1 mile before it got hot enough to act up again. You can check codes more frequently and look for pending codes.

 

[waypoint]

P0304 is a generic misfire code on cyl #4. Trouble shoot it. Swap coil packs 2 & 4 and see if the code goes to p0302. That rules out the igniter. Then swap plugs 2 & 4. Same goal. If it comes back as p0304 and its not electrical, then look at fuel injectors. Thats less easy because you need to remove the intake. Even numbered cyl are on the drivers side

Good step-by-step rule out, I'd add a compression test during the plug removal step.

 

[ieatfish]

Swapped the coil today, no codes yet. If I'm extra lucky it was a poor connection!

 

[waypoint]

Swapped the coil today, no codes yet. If I'm extra lucky it was a poor connection!

How many miles on the spark plugs?

 

[ieatfish]

How many miles on the spark plugs?

I'm actually not sure, I've put about 15k on the 4runner since I bought it. It was one of those things where I thought if it ain't broke, don't fix it. They may be original so I honestly should probably check them...

 

[ieatfish]

P0304 is now back as a pending code. I'll probably just go ahead and replace all the spark plugs just to be sure.

Any recommendations for plugs?

 

[triethylborane]

P0304 is now back as a pending code. I'll probably just go ahead and replace all the spark plugs just to be sure.

Any recommendations?

Plugs possibly, as the gap between the central and lateral electrodes increases, so does the voltage necessary to deliver the current across the gap. This increases the draw on the ignition coil.

Plugs and ignition coils are cheap, even the Denso items. Id replace the coil pack, get plugs, investigate the plugs during the coil pack r&r, then see how things shake out. The engines in the 4Runners are not demanding on the ignition coils (compression etc), but faults can occur on an individual basis within the coil, the ignition wiring, and plugs.

 

[Drcoffee]

If you swapped plugs, coils and still a p0304, I would swap the #2 & #4 fuel injectors. I bet its a faulty fuel injector.

But you have a 2006 which means it can also be a head gasket failing. In the morning before you fire it up, pull out #4 spark plug and see if you can see coolant in the cylinder. Maybe run a swab in there for wetness. That would be a worst case scenario and will cause misfires. Get a head gasket test kit and check for exhaust gasses in the radiator. Its normally #6 but I have seen threads with #4 blown too

 

[ieatfish]

If you swapped plugs, coils and still a p0304, I would swap the #2 & #4 fuel injectors. I bet its a faulty fuel injector.

But you have a 2006 which means it can also be a head gasket failing. In the morning before you fire it up, pull out #4 spark plug and see if you can see coolant in the cylinder. Maybe run a swab in there for wetness. That would be a worst case scenario and will cause misfires. Get a head gasket test kit and check for exhaust gasses in the radiator. Its normally #6 but I have seen threads with #4 blown too

Plugs are next, I should have clarified "Any recommendations for plugs?".

However, for head gaskets I thought was resolved in the '05s?

 

[Drcoffee]

Plugs are next, I should have clarified "Any recommendations for plugs?".

However, for head gaskets I thought was resolved in the '05s?

I thought some early builds in 2006 still had the issue. I have an ‘07 built in oct 2006. Just made the cut off

The original plugs were copper, I changed mine to Denso iridiums and. They run great, but you do need to gap them. They are too narrow out of the box. Too small of a gap will cause drivability issues. Get it right and they will run for 120-200,000 miles.

But before dropping $60 on plugs, check for coolant in the cylinder. You may just end up selling it

 

[AuSeeker]

Plugs are next, I should have clarified "Any recommendations for plugs?".

However, for head gaskets I thought was resolved in the '05s?

I thought some early builds in 2006 still had the issue. I have an ‘07 built in oct 2006. Just made the cut off

The original plugs were copper, I changed mine to Denso iridiums and. They run great, but you do need to gap them. They are too narrow out of the box. Too small of a gap will cause drivability issues. Get it right and they will run for 120-200,000 miles.

But before dropping $60 on plugs, check for coolant in the cylinder. You may just end up selling it

[MENTION=592269]ieatfish[/MENTION] , check the VIN sticker on the driver's door jamb for your build date, if the build date is 12/05 or later your engine has the new design head gaskets and shouldn't have any head gasket failure issues, some earlier build 2006s have the possibility of head gasket failure.

 

[ieatfish]

[MENTION=592269]ieatfish[/MENTION] , check the VIN sticker on the driver's door jamb for your build date, if the build date is 12/05 or later your engine has the new design head gaskets and shouldn't have any head gasket failure issues, some earlier build 2006s have the possibility of head gasket failure.

I thought some early builds in 2006 still had the issue. I have an ‘07 built in oct 2006. Just made the cut off

The original plugs were copper, I changed mine to Denso iridiums and. They run great, but you do need to gap them. They are too narrow out of the box. Too small of a gap will cause drivability issues. Get it right and they will run for 120-200,000 miles.

But before dropping $60 on plugs, check for coolant in the cylinder. You may just end up selling it

Thanks guys, I figured I'd bite the bullet and do the plugs since it hasn't been doing anything else, no lowering of fluid, and I checked for fluid in the cylinder and didn't see any. It is a 09/05 manufacture which is not my favorite thing to realize but I'm not terribly concerned.

Ended up swapping the plugs for some Denso 3421 Iridium plugs. The plugs in the block were half Denso and half NGK. That leads me to believe they were the original plugs!

We'll see how this goes, hopefully it isn't an injector or wiring as others have suggested but seeing how burnt out the old plugs are, I'm optimistic this was the culprit.

 

[AuSeeker]

Thanks guys, I figured I'd bite the bullet and do the plugs since it hasn't been doing anything else, no lowering of fluid, and I checked for fluid in the cylinder and didn't see any. It is a 09/05 manufacture which is not my favorite thing to realize but I'm not terribly concerned.

Ended up swapping the plugs for some Denso 3421 Iridium plugs. The plugs in the block were half Denso and half NGK. That leads me to believe they were the original plugs!

We'll see how this goes, hopefully it isn't an injector or wiring as others have suggested but seeing how burnt out the old plugs are, I'm optimistic this was the culprit.

Definitely original plugs and they have a huge gap, definitely needed to be change because those original copper plugs should be changed every 30,000 miles, hopefully this will solve your issues, for sure can't hurt the way it will run!

Not all early V6s suffer head gasket failure, not sure what the percentage is, but probably not a high percentage or Toyota would of had to do a recall but also high enough that Toyota made the decision to redesign the head gaskets.

 

[Drcoffee]

It looks like mine when I changed then at 222,000 miles, original warn plugs gapped at 0.076