300ZX Fuel injection Diagnosis- by Steve Chong

Checklist

Stalls when the engine is cold (Page EF & EC 85 in the manual)

Finally, if you've drawn a blank so far, here is a list of diagnostic procedures that pertain to hesitation and stalling that are mentioned in the manual:

A Hesitation when the engine is hot (Procedure 7)
B Hesitation when the engine is Cold (Procedure 8)
C Hesitation under normal conditions (Procedure 9)
D Engine stalls when turning (Procedure 10)
E Engine stalls when the engine is hot (Procedure 11)
F Engine stalls when the engine is cold (Procedure 12)
G Engine stalls when stepping on the accelerator momentarily (Procedure 13)
H Engine stalls after decelerating (Procedure 14)
I Engine stalls when accelerating or cruising (Procedure 15)
J Engine stalls when the electrical load is heavy (Procedure 16)
K Lack of power and stumble (procedure 17)
L Surge (procedure 19)
* + Letter above- not mentioned in the manual.

I've shown items affecting the above in the table below:
 

Sometimes it can take a while to get the problem sorted. June 1996:

"Subject: <300zx> Bad hesitation driving ME mad.
Date: Sun, 09 Jun 1996 15:52:16 +0000
From: Ben Mehling bmehling@falco.kuci.uci.edu

My 87 300zxt continues to stutter/hesitate BADLY. The problem is intermittent, and usually shows up when accelerating from top, but can appear at higher speeds (sudden loss of power). I can only guess that the problem has something to do with the fuel system. It feels like (when the stutter occurs) a sudden loss of gas to the engine, and ends up "looking" like I am a newbie stick driver... Here is the current time line repairs:
-bought the car summer of 94
-problem appeared in fall of 94 (Sept or Oct)
*Start taking the car into mechanics (4, in the end: my normal mechanic, a recommended mechanic, a Z expert mechanic, and Nissan service) -None can solve the problem. All offer up solutions.
Items replaced/repaired:
- fuel sender
- rusty gas tank (checked out, no rust)
- tune-up/ standard stuff
- air flow meter
- 02 sensor (problem disappears)
with the last, the 02 sensor, the problem disappeared for 9 months (this repair was made in Jan-Feb 95).
- Reappears in Fall of 95 (ack!! again?!)
- Have the car looked at (even the 02 sensor), appears to be fine.
- Get the Nissan recall info / have the recall done (praying this fixes my car!)
- Get car back, still occurs intermittently
- Now Nissan believes the muffler to be the cause (the muffler just started to have problems and does need to be replaced...but I fail to see how this could be my long term problem...)
- I am considering selling my "baby", it just isn't reliable anymore... (ever?)
Any ideas that would lead me in the right direction are much appreciated. I would prefer to solve the problem and keep this car... But if I continue to throw good money at a problem NOBODY knows how to solve... Thanks in advance for any advice!
Ben
87 300zxt"

With an update October 1997:

"Subject: RE: <300zx> Bad hesitation driving ME mad.
Date: Mon, 20 Oct 1997 09:08:35 -0700

Amazingly enough, I still own the Z, although it mostly sits in the garage (I drive it maybe once or twice a month).

The hesitation still occurs however, and I still consider selling it... but I am sure you know how it is - I drive it once, remember how much fun it is, and then forget about selling it!

I have since had the car looked at by a mechanic (possibly THE most anal mechanic I have ever dealt with). He had the Z for 6 weeks. Made some minor repairs to different fuel sensors and controls, fixed some connections he felt were bad and determined that he was unsure what the problem was...

You can add that to the timeline (in the posting above), as that is the only thing that I have had done to it since that was written.

As far as my own feeling goes.

1) I believe the problem to be in the electrical/fuel delivery system. I just feel like the car has electrical problems and that is what causes the hesitation.
2) If I warm up the car (a solid 5 minutes) the hesitation will probably not occur, at least not really bad. However, sometimes if I drive it hard (even after warming it up) the hesitation will show up.
3) The problem has probably occurred due to the Z spending sometime un-garaged in oceanside community - I think the moist air played havoc on its electrical system. I should have garaged it...

At this point I have easily poured more money into the repairs, than I originally payed for the car, and to no end.

Thanks, Ben

 87 300zxt"