No. 4 Misfire, Please help!
 

I have a 96 4Runner with supercharger, larger injectors andsplit second piggyback computer. It has run fine for years. I'm out of town (and it's Christmas of course) when suddenly it began to miss and the check engine light came on. Read the codes and it said number 4 cylinder misfire. I replaced the plugs, spark appears to be good, switched the coils around trying to identify a bad coil and switched fuel injectors around too. Every time the same code P0304 comes up for No. 4 misfire. I also bypassed the split second computer, no improvement there either. I am without my manual being out of town. Can anyone help?

Thanks,
Ian

RE: No. 4 Misfire, Please help!
 

I also cheked the compression which was fine. It has to be electronic somehow. Maybe a sensor of some sort died?

Thanks for any help and Merry Christmas,

Ian

RE: No. 4 Misfire, Please help!
 

If you are getting good compression on the check for #4 it should be firing. If its not then it has to be a problem with the spark.

Is it a I4 or V6?

RE: No. 4 Misfire, Please help!
 

It is the 3.4 liter V6. I have swapped coils and plug wires as well as swapping injectors. I still get the same message. That is why I think it is something in the computer or sensors. It could be a lack of fuel if the injector is not being triggered or the only other thing I can think of is the exhaust camfollower is busted. Otherwise I would not be seeing the compression I do, about 165 psi.

RE: No. 4 Misfire, Please help!
 

With what you have said i can only think of two things: Fuel line and computer. If the spark is fine, the injectors are working, and it has compression then it is a fuel problem.

Is there anyway you can check if your fuel line to that cylinder is blocked? Possibly some trash got past the fuel filter. I would look over all the lines from the gas tank to the engine to check for any visible damage.

Could you check the codeand run it through a computer to get an explanation of it? Maybe at Autozone or some place like that.If you cant you may have to take it to a dealership to get the explaination of the code.

That is all I can think of right now. Good luck!

RE: No. 4 Misfire, Please help!
 

Got it solved folks. Turned out after all that, it was a plug wire that was failing when the engine was under load. At idle the plug would spark while testing just fine. It never arced anywhere that I could see or hear either so it must have been shorting from the sparkplug cap to the valve cover where I could not see/hear it.

RE: No. 4 Misfire, Please help!
 

[>:]Hmmm correct on the first try again...I like how people listen.