mcheney

Z was running rough at idle, check engine light blinking, OBD came back P0301, installed a new spark plug. Plug was slightly oily and ready to be changed but nothing really bad. Started the engine, no change and P0301 still showing ( yup I cleared the memory). Then swapped the 1 and 5 coil packs, 1 no longer read a misfire but 5 did .. aha! Ran down to the local parts store picked up a new coil pack, installed it ... check engine light was off but the engine still occasionally misfired.

Decided to use my wife's technique of Filipina car repair and pour a bottle of injector cleaner into the tank and took it for a ride.

Kept the OBD plugged in and drove a few miles away from home then back. Check engine light never came on and after maybe a dozen cycles of showing no codes, P0305 showed up but intermittent.

Whereas the performance was significantly better at higher rpms it still idles rough. OBD will read zero, cycle several more times showing zero then misfire on 5 shows up again.

Not sure if I ever paid attention to or remember where the engine normally idled at, but it now seems a bit low at 900 rmp.

So my question .... do I take my Z to the shop or a priest? Anyone know what the problem is?

Thanks in advance for your help!

icer5160

iTrader: (4)

What year is your Z? How many miles on it?

Misfire codes can also be an indication of a bad cam sensor or faulty injectors.

Personally, I would have the vehicle checked out by a professional at this point. You don't want to start dropping serious cash on parts without knowing with great certainty what the root cause is.
-Icer

icer5160

iTrader: (4)

Found a link to a post on another Z forum, this guy went through all the logical steps to solving his misfire. It's a lengthy process and in the end he replaced the ECM to solve the issue. Not a cheap fix, so I would still recommend having a professional look at it.

my350z.com is not letting me link to the other forum. But I'm sure you can find it after some google searching.

zakmartin

How many miles on your car? Has it ever had a tune-up (roughly speaking, anyway)?

mcheney

135K miles bought it used and not sure of the history. It has run flawlessly for the past 2 years. Was considering a tune up before the recent issue. Thank you for your feedback. I have no desire to run down possibilities not knowing enough about it.

Year - 2005

zakmartin

Yeah, sounds like it's probably due for one. My only advice is to stick with OEM parts if you can afford it.

mcheney

Awesome advice all, thank you! Will start looking for a shop in my area.

PerfZ

iTrader: (3)

Tuneup pretty much consists of replacing spark plugs and intake filter. There really isn't much else to do - easy to do yourself for most folks anyway. Other than moving some wiring harnesses to pull the coil packs which is just labor intensive - and do them one at a time so you don't misconnect them - that has happened frequently it seems.

mcheney

Thank you, PERFZ

This morning I started it up in the driveway and for the first time it threw a P1111 code, control solenoid valve.

Could this have been the culprit all along?