Montego Murph

iTrader: (1)

Hi everyone, it's been a while but I'm back.

About a year ago I sold my beloved 2001 i30 to a good friend. We had the understanding that if the car acted up, I'd be glad to take a look at things since I knew the car to mental illness-levels, having been around it since new.

She messaged me the other day with an issue. It was running rough, described as a bop-bop-bop-bop feel. A code scan told us P0304 (Cyl 4 Misfire) and P1320 ("Ghost Code" for ignition issue.) Those codes, the driving symptoms, and TCS/Slip/CEL lit up on the dash tells me that a coil went bad.

The car was also LONG overdue for an oil change (may be as much as 6 months late,) so she had that done while she was out yesterday. She said it was running fine immediately after the oil change, and on her way to pick up the new coil today, says it's still running fine.

I cannot think of any reason for this, but is there any possible link between an overdue oil change/low oil pressure and an engine misfire condition on only one cylinder? There is absolutely no reason on earth why this should happen, but these cars came with an extra jar of weird from the factory. I would understand if the engine had some sort of variable valve timing that was thrown off by low oil pressure, but that's not the case.

Today, aside from the CEL lit up, the car is running fine, no TCS/Slip lights.

What should I advise her to do?

DennisMik

iTrader: (2)

While what happened is interesting, going a long time between oil changes won't cause a misfire. A misfire is an electrical problem, something caused by an oil problem is mechanical. As long as the oil level didn't drop to some dangerously low level, there would be no mechanical problem.

I have no explanation for the misfire going away after an oil change, but I suspect it will be back.

stevesmax

When a coil started to fail on my 4th gen Maxima, it was very intermittent, and could go for days without missing, then miss intermittently every day for a week. It is possible that the coil on your old car may have the same issue, and is just a coincidence it is running fine since the oil change.

rodent_infested_03

Long term, yes it will. Slacking on oil changes will clog the tiny oil return holes in the pistons with sludge and carbon. That will cause oil overflow in the piston. That oil overflow will be consumed, which fouls the piston rings. They stick. Which makes consumption even worse. Consumption gradually increases, eventually fouling the plugs with oil and causing a misfire. Things get worse and worse until the engine stalls with blocked catalyst.

However, its just as likely the middle front coil is bad. You can verify by swapping that coil left or right, see if the code changes. If the code changes, you know. The other code indicates a problem with the connection. Check all coil connectors. The coil is 2 piece. So depending on temps, expansion, etc the connection can be good or bad. Appear or disappear. you could try removing the coil, pull the shaft off (part that goes down to the plug) , and applying some bulb grease between the 2 parts. Maybe they spilled or hit something? Take the cover off and look around.