Question about throwing two misfire codes (1 Viewer)

[Rooki]

Greetings, All -

I hope you're all doing okay so far in these hard times.

I just started my '01 LX470 and it ran rough and started blinking the check engine light. The codes were P301 and P308, misfires in cylinders 1 and 8. I'm out in the sticks with one ignition coil on hand. I had to drive about 8 miles to get back to camp. The check engine light stopped blinking but went to steady illumination at about 50 mph, then went back to blinking when I slowed down again.

Since it seems unlikely that two coils would go bad at once, my plan is to start with swapping the #1 for the new one and if that doesn't work then the 8 (just because the back one is harder to get to, if I recall from the last time I did this). The last time a coil pack went bad the truck ran with pretty much the same roughness it is now, adding to my suspicion, and hope, that this is just a bad coil. Plugs were sparkly clean and gaps were spec the last time I checked about 15,000 miles and seven months ago.

But my question is, can you get a code for two cylinders with one bad coil? Does this sound to you like the coil problem? Or, do the two codes suggest anything else that you might suspect is going on?

Thank you, and stay safe,
R

 

[JunkCrzr89]

can you get a code for two cylinders with one bad coil?

No, one bad coil would not cause misfire on two cylinders on different banks. However, it’s not improbable that 2 coils on different banks would fail at about the same time, though somewhat unlikely. I’m inclined to suggest you have a fuel issue (don’t want to jump the gun just yet), but I’d go through the coil swap-around procedure first if I were you. Are you on original fuel pump, filter, etc. still?

 

[Rooki]

Are you on original fuel pump, filter, etc. still?

I'm probably on original fuel pump and filter. I bought the truck at 135K miles and am at about 245K now. I'm checking previous service records to see, though it hasn't been done while I've had it. Timing belt, water pump, etc, but none of that...

 

[JunkCrzr89]

I'm probably on original fuel pump and filter. I bought the truck at 135K miles and am at about 245K now. I'm checking previous service records to see, though it hasn't been done while I've had it. Timing belt, water pump, etc, but none of that...

I suggest going ahead and swapping the one new coil around between 1 and 8 to see what happens. If codes return despite new coil, then I’d bet you have fuel system issue - clogged injectors, fuel filter, or weak (failing) fuel pump.

 

[Rooki]

I suggest going ahead and swapping the one new coil around between 1 and 8 to see what happens. If codes return despite new coil, then I’d bet you have fuel system issue - clogged injectors, fuel filter, or weak (failing) fuel pump.

Okay, wilco, that's what I'll do, and thank you. This site directed me to a few other posts about coils in which people seemed also to get codes for more than one cylinder when they only had one bad coil. Is it unlikely that the system would be delivering those?

 

[JunkCrzr89]

This site directed me to a few other posts about coils in which people seemed also to get codes for more than one cylinder when they only had one bad coil.

Yours are on different banks though. Cylinders 1 and 8 are not on the same bank and therefore should be completely unrelated as far as electronics go. If your misfires were on cylinders 1 and 3 instead (same bank, neighboring cylinders), then they could be related.

 

[JunkCrzr89]

Might find some useful info in this list of threads: Rough Idle/Sputtering/CEL/Misfire = Coil pack problems

 

[marshotel]

The same thing happened to me yesterday in my 98 LC:

It started running rough and the CEL came on. The codes were P0303 and P0306 (misfires on cylinders 3 and 6). I also had code P0300 (random misfire).

I put the new coil on cylinder #3 and that did not fix it, so I moved the new coil to cylinder #6 and that fixed it!
I think it is not uncommon for the OBD system to throw a few different codes for misfires on a single cylinder.

This is the second coil I have replaced in the past 6 months (last time it was #4).

I wonder if I should just replace the 6 remaining original coils with new Denso coils, and change the spark plugs as preventative maintenance.