misfire !!!! Frustration

Nissan 300ZX technical discussion forum: Maintenance, performance, installations, modifications, how-to's and troubleshooting.
SHAZ_300ZX
Posts: 2
Joined: Fri Aug 01, 2014 9:59 am
Car: 90 300zx n/a 2+2

Post

ok guys how are you all doing, im new here as you can tel ive owned my 300zx for about 5 months now... so lets start i have a random misfire that has always been around since day one, it passed emissions no problem with amazing numbers but always felt that it hasnt been pulling nor idling correctly.

I changed the plugs to the proper n/a ngks, i have ran a induction service on the motor, meaning cleaned the valves iac throttle body,. i have used the "bg 44k" cleaner from specialty z for the injectors, replaced all the injector connectors. changed the mass with another used mass and bought a AMS mass air flow as a backup since it was 60 dollars from a private seller bnib. umm crap i even checked the coils, mined you guys i didnt check ohms on injectors yet nor the coils out voltage. after doing all that the car ran good not great, the misfired was noticable at idle mainly and the car did lag a bit. I forgot to mention i swapped the ptu with another.

Now heres the messed up part, i was driving home from a z show and it started raining , i ended up on a street where all the grates were flooded over and i went through about 2 FEET OF WHAT, THE CAR DIED , I STARTED IT BACK UP IT RAN , BUT s***, GOT ON THE SIDEWALK AND ON TO A DRY STREET .. DROVE FOR A HOUR AFTER , CAR RAN NORMALLY. THE NEXT DAY AS IAM DRIVING INTO WORK IT STARTED HAVING A HEAVY MISFIRE AND KEPT GETTING WORSE, NOW I CHANGED THE MASS AIR FLOW TO THE NEW ONE AND THE CAR WANTS TO IDLE HUNT AND STALL. .. GUYS I DONT KNOW WHAT TO DO. I HAVE A CODE READER AT WORK THAT WE USE ON THE OBD1 CARS AND I PULLED A BANK 2 O2 SENSOR CODE , BUT THATS IT.. PLEASE ANY HELP IS APPRECIATED OR SUGGESTIONS.
:wtf2:


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ezb57e
Posts: 471
Joined: Sun Jun 29, 2014 9:02 pm

Post

Welcome to the forums.
Could water have gotten down into the spark plug wells?
Connector for the transistor pack, and CMPS?
At some point I would do a good, accurate compression test as a baseline for your motor, regardless of anything.
Good luck

User avatar
icemaninlv
Posts: 31
Joined: Tue May 27, 2014 1:46 pm
Car: 91 NA 300zx 2+2

Post

Check your ptu! Is it square and silver ish or black diamond shape

nissanfreak12
Posts: 1709
Joined: Sun Jan 23, 2011 4:07 pm
Car: 92 300zx 2+2 TT
Location: Denver, CO

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I had this issue before, the connectors or even the MAF wet, you need to let them dry out for quite a few days. You can speed up the process by using a hair dryer on ALL sensors, keep it on the low setting, don't want to melt anything. Mine drove fine after about 3 days.

Your misfire could be your injector, ohm test each one or do a power balance test and what ever cylinder doesn't cause a change, that is the problem cylinder

SHAZ_300ZX
Posts: 2
Joined: Fri Aug 01, 2014 9:59 am
Car: 90 300zx n/a 2+2

Post

thanks guys, I'LL TRY ALL YOUR IDEAS WISH ME LUCK.


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