Hi All, New to the site.

I have a 2002 I35 with the dreaded p1320 code.

I have a misfiring #3 coil.

I don't know the firing order, but I think its the middle rear coil.

Do these motors have front and rear specific coils ?

I'm also installing Denso Platinum plugs. ya'all think their ok ?

Then I;m installing new upstream and down stream Bosch o2 sensors.

Hopefully this should help the sputtering idle ?

Opinions wouls be appreciated.

Thanks, Ron

 

The firing order is 1-2-3-4-5-6 but has nothing to do with the subject/problem.

The cylinders are numbered 1-3-5 on the right bank and 2-4-6 on the left bank. Because the engine is transverse mounted, the right bank is next to the firewall and cylinder #1 is on the passenger side. The left bank is towards the radiator and cylinder #2 is on the passenger side. And yes, you are correct that cylinder #3 is the rear middle.

Because of the design of the intake manifold, the ignition coils for the left and right banks of the engine are different. The rear (right) bank (cyls 1-3-5) have longer spark plug boots in order to reach the plugs. If you got the specific code of P0303, go ahead and replace that one. If you want to experiment first, swap cylinder #3 coil with cylinder #1 or 5 coil and see if the code changes to the other cylinder (P0301 or P0305).

The Denso plugs should work fine.

O2 sensors won't make one bit of difference as to how the engine idles/runs. They are only there to report problems when the fuel mixture is not being completely burned in the cylinder. If you have an O2 code, don't worry about it until after you have fixed the P1320 problem. It may go away when the engine is running properly.

 

Great thanks for the info. I'll do the coil and plugs first then clear the codes and go from there. Thanks again.

I'll report back on my progress