P0304 code

Hello,

Doing a search I see that this has come up a number of times. Well today the check engine light came on and ODB says P0304 - i.e misfire on cylinder 4. On 4Runner # 4 cylinder is the middle one on the driver side.

I checked the plug and it is good. The plug wire is good and I get a spark. Cylinder 4 is not receiving fuel. I tested this by installing the plug w/o the ignition wire and ran the engine. To be more specific I had the #4 ignition wire attached to an extra plug that I had and with the body grounded, I ran the engine (did not want to potentially damage the coil). Anyway afterwards when I removed the #4 plug, I found it to be dry so no fuel.

I removed the upper/lower manifolds and have tested the resistance for all three injectors on the driver side. They all read 14.7 ohms. I also checked the power at the injectors (with the switch on) and they're all receiving power. I am now stymied what to do next. I was going to remove all the injectors and have them be tested. Does anyone have an alternate suggestion on what to do next?

Thanks,
Matt

 

I think you listen for the injectors noise? Not sure how?

 

The injectors sit under the manifold and with the manifold off, one cannot run the engine and listen to the injectors ticking, at least not on the driver side. With an exposed injector you can use a stethoscope or just lean a long screw driver against the body.

I thought about swapping the #4 injector with another one and see what happens. I hate doing this because this means I'll have to put the engine back together and run it again!

 

Well, you can just buy another injector, swap it in and put her back together and see.

There are places online which will swap you a fully tested/flow rated set for your OEM ones for like $300.

 

I pulled all the injectors. The 4th injector's lower body was wet whereas the rest of the injectors were dry. I think this means either the 4th injector is cracked or has a bad o-ring or ...
Since my last note I have found service providers that will refurbish my own set. I will be doing that.

 

Just an update. Sent all my injectors to motorwestperformance.com for injector testing and refurbishment. They did an eval and sent a neat summary report showing the following. They recommended that I replace both injectors 3 and 4 given their flow rates and the electrical issues that varied during testing (not shown here). They had refurbished Toyota injectors as replacements for the two bad ones. I followed their recommendation and will receive all my injectors including the bad ones plus the two refurbished units. Cost wise this was reasonable ($165, ($15 mailing cost for me, $150 Motor West charge)). Time is a huge factor though. By the time I receive the injectors, it would be a 2-week long process. Hopefully this was the reason behind the P304 error once I receive the injectors and install them.

 

NEAT!

Yeah, #4 and #1 are looking like a couple of duds.

The price seems very reasonable.

 

One final update. Installing the injectors was a lot easier than I thought it would be. All is well with the car now.