Narrowing Down a Misfire - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

[email protected] · 07-07-2014, 09:03 AM

Been going through the steps on figuring out what exactly could cause a misfire in a 90 Z32. So far I narrowed it down to Cylinder #3 . at first thought it was the coil pack, (disconnecting it did not change the way it ran. )Ended up switching it with another coil pack that is running but nothing changed. Next I removed the spark plug in cylinder #3 thinking it could be the spark plug it self. Taking out the plug I saw it was all black looking burnt which lead me to believe that cylinder is running rich being caused by a faulty fuel injector.I did switch spark plug ( which are NGK ) with another cylinder to see if maybe that plug would misfire in another cylinder, it didn't. So faulty injector? Has anyone heard or experienced anything else that it could be. Haven't had the car for long, plugs have been recently changed by last owner. Car idles around 1ooo. I did some reading for about a week before posting and diagnosing the problem. Haven't pulled codes yet though that should've been my first step. I'm new to Nissans or V6 ( vg30 ) always had Rotary's. Hopefully I can figure this one out. Thank you.

JeeBus · 07-11-2014, 06:15 PM

The vg30 engine electrical system is notorious for corrosion.

Try cleaning the CAS plug, PTU plugs, and most definitely the injector plugs.

But since you've narrowed it down to cyl. #3, start with just cleaning the injector pins and the harness pigtail for that injector.

More than likely your car has "old style" square clip injectors which are prone to failure from corrosion and the ethanol content in the gas of today.

cotbu · 08-21-2014, 08:18 PM

You were on the right track, you should just concentrate on the cylinder problems that are easier to diagnose, like injectors, ohm them, check for leaks and then swap them around. And If all it is, is a leaky or bad injector you wouldn't have to pull the wiring apart, or swap out the cas, at least for now. Assuming the other injectors, and plugs fire.

Sent from my Highly Tuned Galaxy S3.4!!!

07-07-2014, 09:03 AM	#1
[email protected] Join Date: Jul 2014 Posts: 4 Trader Rating: (0) Feedback Score: 0 reviews	Narrowing Down a Misfire Been going through the steps on figuring out what exactly could cause a misfire in a 90 Z32. So far I narrowed it down to Cylinder #3 . at first thought it was the coil pack, (disconnecting it did not change the way it ran. )Ended up switching it with another coil pack that is running but nothing changed. Next I removed the spark plug in cylinder #3 thinking it could be the spark plug it self. Taking out the plug I saw it was all black looking burnt which lead me to believe that cylinder is running rich being caused by a faulty fuel injector.I did switch spark plug ( which are NGK ) with another cylinder to see if maybe that plug would misfire in another cylinder, it didn't. So faulty injector? Has anyone heard or experienced anything else that it could be. Haven't had the car for long, plugs have been recently changed by last owner. Car idles around 1ooo. I did some reading for about a week before posting and diagnosing the problem. Haven't pulled codes yet though that should've been my first step. I'm new to Nissans or V6 ( vg30 ) always had Rotary's. Hopefully I can figure this one out. Thank you.

07-11-2014, 06:15 PM	#2
JeeBus Leaky Injector Join Date: May 2011 Location: ATL Posts: 66 Trader Rating: (4) Feedback Score: 4 reviews	The vg30 engine electrical system is notorious for corrosion. Try cleaning the CAS plug, PTU plugs, and most definitely the injector plugs. But since you've narrowed it down to cyl. #3, start with just cleaning the injector pins and the harness pigtail for that injector. More than likely your car has "old style" square clip injectors which are prone to failure from corrosion and the ethanol content in the gas of today. __________________

08-21-2014, 08:18 PM	#3
cotbu Post Whore! Join Date: Sep 2005 Location: SWFL Age: 49 Posts: 3,318 Trader Rating: (3) Feedback Score: 3 reviews	You were on the right track, you should just concentrate on the cylinder problems that are easier to diagnose, like injectors, ohm them, check for leaks and then swap them around. And If all it is, is a leaky or bad injector you wouldn't have to pull the wiring apart, or swap out the cas, at least for now. Assuming the other injectors, and plugs fire. Sent from my Highly Tuned Galaxy S3.4!!! __________________ LoverTechnologies "Half Broken Things!"