Deuce7

I'm trying to fix this car so it's in great condition. Base with navigation 2006 TL. It has ~170,000 miles. It just had the full water pump/timing belt service done after a leaky pump sent it in to the dealership for repairs.

Not sure if it's related, but it had an intermittent engine light a couple years ago for a faulty catalytic converter (#3 I think). It was intermittent for a couple years. But that cleared up on it's own without being replaced. I have no clue why. The trouble code does not come up any longer when checked.

So I had an engine light on for a few weeks before the recent service. Got it back and put it on my OBD2 computer. It said it had a misfire in cylinder #5 (PO305). I replaced the spark plug and ignition coil. Car drove flawless for 3-4 days! Problem solved, or so I thought so I cleared the code and engine light. Drove great for a few days and around 125 miles.

So I go to start it this morning and it starts rough and idles rough. Engine light blinks in the garage and comes on solid while I'm driving. I get home tonight and hook it up again to the diagnostic unit. NOW it shows a misfire in cylinder #2... The code was P0302.

So what to do? Just keep chasing this misfire and replace ignition coils and plugs? Or could this be caused by something else like the computer or injectors? Is it odd that after changing coil/plug in #5 that it would be so super smooth, just to have it happen in another cylinder a few days later?

Thanks!

Deuce7

And if I'm going to replace an ignition coil again, which is better? A new aftermarket one or a used OEM from eBay? The price difference is substantial. Used OEM are $10 each, aftermarket new are $25-$35, and new OEM are $125.

Deuce7

Friend at work thinks the misfire codes have to do with the early catalytic converter errors. He thinks old or bad oxygen sensors can cause a misfire via the fuel injectors, assuming the cat isn't bad itself.

Is this a problem best left for the dealer? I plan to sell this car in the next month. I don't want to spend any more than I have to at this point, but I doubt it'll sell for nearly as much with the engine light on. And it's in very nice condition. This is the last and only problem that needs fixing, and it'll be a damn nice car again.

horseshoez

iTrader: (2)

A few comments in no particular order:

• A bad cat is definitely in play as the cause; it is pretty rare they fix themselves.
• Ignition coils, when they go bad, are often misdiagnosed by the OBD-II system regarding which specific coil is bad. It isn't at all unusual the have a bad coil, and yet have the system diagnose one, two, or even three other coils as being bad.
• The only real way to diagnose a coil is to disable one coil at a time and track the problem manually. When you disable the coil which is bad the engine won't run even worse than it was before the coil was disabled.
• OEM coils are widely reported as being the best; Denso are also considered as good (and if I recall correctly, may also be the OEM part without the Honda name on them).

Deuce7

justnspace

iTrader: (1)

keep the car running. unplug coil pack one at a time. engine note should change upon disconnecting coil pack connection. if engine note does not change...there's your bad coilpack

thoiboi

+1 on OEM coil per horsie. Sounds like a dead coil pack so follow Justin's troubleshooting by disconnecting one at a time.

Deuce7

truonghthe

OEM part supplier is Hitachi, Denso is a upgrade IMO as they are OEM ignition parts for Toyota/Lexus.

horseshoez

iTrader: (2)

Good to know, thanks.

nfnsquared

Was the #5 plug loose when you changed it out?

#2 and #5 plugs are notorious for coming loose. I'm guessing the shop pulled the plugs to hand crank the engine when they replaced the TB. Maybe they didn't get them torqued back sufficiently?

Deuce7

justnspace

iTrader: (1)

cat#3 doesnt have any sensors on it.

so it was the primary cats...either bank 1 or bank 2.