1996 300zx na - left side driver from US - rough idling after disconnect and reconnect of the injector connectors ( for resistance testing).

Car was running smooth before and suddenly started rough idling after doing this injector connector ohm testing, it does look like all injector wiring connectors are seated properly again. does this procedure somehow reset the ecu idle setting to factory tuning ? .. i do remember i had this issue before with this car and i had a very good z mechanic at that time and he was was able to fix it quickly .. think it was the idle screw adjustment. And possibly disconnect and reconnect of the idle valve. But not entirely sure about the right procedure. 
 

I am posting some pics and could use some help identifying what is what. 

Also, there was supposed to be a engine by numbers diagram at this link, but the attachment says nothing found .. was that relocated somewhere else ? 
 

 

My eyes hurt.... its all on the wrong side.... at least it's not all upside like the Aus model.... ?

I would work back through what you disconnected checking connections and looms. Reconnect everything, check for broken plugs and green electrical gunk. Have you run the engine codes yet?

The female part of the connector (arrowed) in picture below looks to be incorrectly seated (and the wrong way up).

Edited January 28, 20223 yr by AndrewG

Good eyes Andrew!

Thanks Andrew, i will check on it ..

Realnips, thx,  havent been able to run codes on it yet, my old obd2 scanner is not working on this 1996z .. ordered another one, should have it in the next few days. 

12 hours ago, SamSpade said:

Thanks Andrew, i will check on it ..

Realnips, thx,  havent been able to run codes on it yet, my old obd2 scanner is not working on this 1996z .. ordered another one, should have it in the next few days. 

Z32 isn't OBDii standard. You'll need consult or NDS to read codes (or use the ECU flashing method). 

If you can buy one of these:

I got mine from eBay years ago with a usb cable. It was a bout £14. I was warned about the cheap ones, but so far it hasn't let me down....

Then you can download either:

• Nissan Datascan I (http://www.nissandatascan.com/)
• Conzult (https://conzult.com/)

These have free versions that are limited or pay for the full version. Both have their pros and cons, but both allow for free reading/clearing of codes. You then hook the reader up the usb, then on to your laptop. Open up your software of choice and read the codes!

Failing that, you can read the codes like this (but is more of a faff and is easier with a friend in the passenger footwell):

https://conceptzperformance.com/wiki/index.php/ECU_Diagnostics

Edited January 29, 20223 yr by TheRealNips

Actually z32 1996 is the first year they made it obd2 in the US, apparently  thats not true for the rest of the world. Its only in gold ol US of A. To add to that,  I am in california with even tighter emissions regulation.
 

anyway, ran the codes and i am getting 3 codes

P0305 - 5th cyl ignition ?

P0325 - knock sensor 

P0171 - lean bank 1

 

all that was done before this problem started was we disconnected all the injector connectors and did resistance testing with ohm meter. They all checked out fine. But when putting it back we had trouble seating the #5 injector connector back properly.. due to lack of space ..but eventually it went it. And this problem started ever since, rough idle and the knock.

i am going to disconnect and reseat all the injector connectors again ( this time with the balance bar removed .. so we have more room. Do i need to remove upper plenum too ? .. 

I was reading how painful and costly the knock sensor code can be .. but hopefully if i reseat the injector connectors properly the knock will be gone ? ..

also, i dont know if my previous mechanic relocated the knock sensor on my car, i will have to find out..

 

any advice on dos and donts for experience ?
this is 1996 NA

 

 

 

It does sound like that is the root of your problems. No fuel in chamber would cause ignition error and knocking and then the bank would run lean. Connectors have a habit of going brittle and cracking. Might be worth replacing the pigtails for injectors and plugs. 

I had no idea about OBDII on 'murica zeds, you learn something everyday. Thank you!

Fixed !!! .. one of the injector connector pins was bent to 45 degrees and wasnt making contact .. to the harness connector.  Reseated the injector connector .. rough idle gone, knock gone. Codes cleared .. and running smooth again. 
 

Car runs great .. just has low compression in a few cyl. Think about 2 of them are running at 120 instead of usual 160. But cant do anything with that without a rebuild. Just going to hang on to it for now. 
 

Going to test drive the new z in a few months and decide what i am going to do then ? .

thanks for the support on the forum.

Edited January 29, 20223 yr by SamSpade