I can't figure this miss out.

[mplsdunk]

96 v6 with 190k on it. It's missing on cylinder 4 error code p303. So far I have new plugs, wires, both 02 sensors and a new coil pack on cylinder 4. I'm completely lost. I just bought the car so I don't mind replacing all that anyway but now I don't know what to do.

Fuel filter? I have one but I don't have a 14mm flare nut wrench yet. I also don't think that would make cylinder 4 miss only.

 

[02SE]

Well, your code is a cylinder 3 misfire.

Here's a diagram of the cylinders, and the correct plug wire routing:

 

[gamefreakgc]

96 v6 with 190k on it. It's missing on cylinder 4 error code p303. So far I have new plugs, wires, both 02 sensors and a new coil pack on cylinder 4. I'm completely lost. I just bought the car so I don't mind replacing all that anyway but now I don't know what to do.

Fuel filter? I have one but I don't have a 14mm flare nut wrench yet. I also don't think that would make cylinder 4 miss only.

The plug wires are confusing, I'd double check the wiring. I just replaced them on my new to me 4Runner and I messed them up royally. No harm in that, just slightly frustrating!

And you don't need a flare wrench to replace the fuel filter. It just makes it easier and less likely to strip the nut. I did it just fine without, but I have 0 rust on mine.

 

[Millerad1651]

It could also be the fuel filter or a fuel injector. Throw some Lucas Injector cleaner in the tank, and fill it up with 93. Drive for a bit and see what happens.

I just got through this with my wife's 98 at 310k. I had a misfire in cylinder 1, so I replaced all the plugs (ended up being AutoZone single electrodes) but still had the problem. I then changed out the coil, didn't fix it.

I threw the injector cleaner in and so far so good. It only seemed to studder at 45-50 mph, so it seemed like a fuel issue. Its been a week or so, and so far so good.

 

[mplsdunk]

Ok so I have the new coil pack on cylinder 3. All the wires are on right. I used oem wires. The head gasket was done 40k miles ago. I used an oem coil pack too. The old one I took out was oem also. It obviously didn't fix the problem so I'm thinking I have an extra good coil pack... The coil pack on cylinder 1 has obviously been changed by on off brand. I'm going to take that out tonight and throw in my exta oem one.

Then I'll get some injector cleaner through it and do the fuel filter too. I know you don't need a flare nut wrench but I live in mn and it's never been changed. I've been spraying it down with pb blaster to make the job easier.

Thanks to that diagram I realized I switched the wrong coil and I need to do the suspicious looking one because that runs cylinder 4.

 

[mplsdunk]

lol I got a a flare nut wrench to be safe and it immediately rounded off the bolt. So I guess I'll get a fuel line too. I really doubt it's the fuel filter causing the miss but it needs to be done. I did throw some Lucas in the tank and filled it up and removed the sketchy coil pack so we'll see. Next I'll order injectors from rock auto if it comes back. It's not always happening so that's why I figure injector now since the ignition is all good.

 

[JayRolla]

After doing the fuel filter and cleaning out injectors if it dont fix the issue you may want again look at head gasket. Do a leakdown compression check.

 

[gamefreakgc]

lol I got a a flare nut wrench to be safe and it immediately rounded off the bolt. So I guess I'll get a fuel line too. I really doubt it's the fuel filter causing the miss but it needs to be done. I did throw some Lucas in the tank and filled it up and removed the sketchy coil pack so we'll see. Next I'll order injectors from rock auto if it comes back. It's not always happening so that's why I figure injector now since the ignition is all good.

Aww, that sucks man. Did you get metric wrenches? My non-flare wrench fit just fine I just had to be careful not to push at a funny angle. I think It used a 14mm and 12mm, but that could be wrong. I used a breaker bar for more leverage and control (my breaker bar is a long section of hollow pipe I slip over my wrench, probably the most useful "tool" in my garage!).

I bet switching over that coil will do the trick. If this helps at all, just remember passenger's side is odd and driver's side even, and start counting from the front of the vehicle. Then you can remember which one is which without the chart.

 

[mplsdunk]

Yup that did the trick! Now I have all oem ignition. Totally new car, it was some generic black coil pack. Didn't even have a brand name. Idle is rock solid along with no more random loss of power.

Yeah the bolt rounded off immediately so rather than dick with that I'll just put a new fuel line in with the new filter. I'm going to handle that once it warms up a bit.

I'm gonna go on a limb and say this is the original filter.



It was a 14mm flare nut wrench, that nut is just toast. And yes that does help me remember the cylinder numbers. I doubt I'll ever forget them now.

Thanks all!

 

[AZ4Running]

Could be a head gasket, it is possible. Op did you have the heads resurfaced when the head gaskets where replaced? Pretty important to do that. If you plan to cleaan the injectors dont just do the bottle in the fuel tank, those dont work well enough. You need to either do an injector flush which most people dont have the equipment to do so or you need to pull out the injectors and send them out to be cleaned. If it is an injector issue then a new injector is often the easiest solution. I would start but running the engine and unplugging the #3 injector if there is no change in how the engine runs then its the injector, this only works if its not a dead miss. If still no luck there then a compression, leak down and block test is next on the list. Good luck i hope you get ut figured out.