vh5150

iTrader: (5)

Ok, I'm at a loss. Car is an 05 N/A. Just changed my spark plugs using the NGK Platinium plugs (the stock replacements). All coil packs looks good and fit fine, everything torqued to spec, all electrical connections ok, no vacuum leaks. On startup, car runs very rough. It's very rich as there is an odor of gas. Throws a flashing CEL but if I rev it a bit, that goes away. Old plugs all looked ok except for #5, which had a small amount of oil (next project is the spark plug tubes apparently). Can ran GREAT with the originals, but not so much since the swap. Any ideas? Thanks. (and yes, I searched first).

Cux350z

iTrader: (162)

you probably mixed up two of the coils on the drivers side. The connectors are easily swapped. Did you mark them prior to removal or do 1 by 1?

vh5150

iTrader: (5)

Yes I did Cux. One at a time. That's why I'm so puzzled.

harman850t5

iTrader: (8)

Did you check the gaps on the new plugs? I'd check for codes to see if it'll at least tell you which cylinder to look at and go from there.

Bigsyke

I have experienced something similar as well, although not as extreme.

My plugs were 90k old, swapped them out for iridium's. Car ran like crap after. No top end.

vh5150

iTrader: (5)

Ya. I'll have to plug the code reader in it and go from there I guess. I thought the NGK's came pre-gapped at .044 and that you didn't touch them. No?

harman850t5

iTrader: (8)

You're not supposed to adjust them, but it's always a good idea to see where they're at.

vh5150

iTrader: (5)

Plugged in the OBD scanner. Have the PO300 "random misfire" code, but not a specific cylinder. Also showed "C" code (catalytic conv), "EV" (evaporative system monitor), and "O" for an apparent issue with the oxygen sensor(s)? All this from a plug change? Or is it it just a coincidence that other things went wrong at the same time that the plugs were changed? Any help would be greatly appreciated. Thanks.

Nathan

When fitting new spark plugs it is very easy for the plug to slip out of the spark plug socket & fall down the plug tube closing up the gap. You don't notice the gap closed up when you reinstall.
If as you say you are sure you did not mix up coils then it is almost 100% to be a faulty plug or plugs, either by manufacture or no gap.

vh5150

iTrader: (5)

So I pulled the spark plugs to verify the NGK gap. Everything is normal (.043). Next I checked the coil packs with a multimeter. I get a reading between terminals 1-3, 2-3, and a zero between terminals 1-2. Is this correct? Rechecked vacuum lines, electrical connections, etc. All appear ok. Never touched the MAF or TB. I'm about to give up and take it to the dealer or a local shop. Very frustrated.

str8dum1

iTrader: (11)

flashing CEL is bad, means gross misfire and can ruin your cats quickly.

did you take the intake manifold off? make sure the MAF sensor is plugged in?

vh5150

iTrader: (5)

Thanks. No, I haven't taken the manifold off. Ya, the MAF sensor is plugged in. I'm just running out of time to troubleshoot this myself. It sucks that doing a simple plug change somehow opened Pandora's Box. Frustrated beyond belief.

str8dum1

iTrader: (11)

ya sounds like time to take it to someone to look at it. you certainly dont want to drive it if you are getting a flashing CEL

marcster13

I changed out my plugs with the Iradiums and they were not pre-gapped at .044, more like .39. So always check the gap before install.

Did you happen to clean the throttle body while you had the air tube off? I've read posts on here that some people had issue's after cleaning it. Just a thought.

Cux350z

iTrader: (162)

I would still double check that all the coil pack connectors are on the right coil packs...verify with cylinder numbering and FSM wire colors

myfirstzcar

Did you lose the springs from within some of the coil packs?