My formerly perfect 2000 TL has developed a misfire in Cyl. #1 :-( I guess for 190k miles I shouldn't be upset.

What's the best order for troubleshooting?
1. Check plug
2. Check coil pack
3. Check Plug wire
4. Check injector?

Thoughts and questions are welcome.

ETA: #1 is passenger side, closest to firewall, right? Hardest one to get to, right?

 

Firewall
123
456
Radiator.

 

Also you can remove injector from the list those things were built as tanks unless you were using lead gasoline or something they are fine. Also the Coil pack wire is out of the question unless a raccoon went inside your bay and made a mess..

Usually our Misfires come from Damaged or worn out Coil Packs! Something as silly as an unplugged coil can be too.

 

instead of the "wire and injector" you can check the EGR valve!
check to see if its not fouled up with carbon

 

I would check most everything off that list. I would start by swapping the coil pack from the #1 cyl to a different cyl and reset the ECU. Drive it and see if the cel comes back on and if the code followed. If it does the coil pack is bad.

Also when was the last time you put new plugs in.

 

Plugs changed at 120,000, so they have 70k on them. They're due for a change. Coil packs--don't know. Might be original with 190k on them.

 

So, I reset the ec, then swapped the coil packs between 1 and 4, to see if the code would follow the pack or not. Tat should tell whether its the plug (misfire in 1) or the pack (misfire in 4), right? But I got code P1399--misfire in any cylinder.

Well, that didn't help. Replacing plugs now, just cuz they need it. Any other suggestions ?

 

Success!

Replaced plus, still missing. Replaced the coil on #1. Still missing. Examined plugs more carefully. #6 looks moist. Swapped its coil, and cleaned the EGR. It didn't look bad.

But, it stopped missing. So it was either #6 or the EGR. Glad to have it back to normal.