I have a '90 2+2 NA. I finally got my car finished regarding my body kit and new paint. This issue of stalling started before I took it off of the road for paint. This happens when its cold and when its warm, but is inconsistent. I push the clutch in to stop, and the idle drops irradically, sometimes it dies, sometimes it does not. I have recently installed a cold air intake, before this issue, and it was fine before and after installation of Cold Air Intake, and I cleaned the throttle bodies in the process of the installation of the Cold Air Intake. I have also replaced the Throttle Position Sensor (TPS), without and change. I have also replaced the O2 sensors awhile back. I have been running fuel injection cleaner with every oil change. I did recently picked up new OEM NGK plugs, though haven't intalled them yet. Got any Ideas?
Thanks!
Kevin :

 

I experienced the same problem that you described. My motor would never die, but when approaching stops and pushing the clutch in the idle would drop down to almost stalling, then stumble a little before catching and coming back up to the correct idle speed.

After cleaning my air filter and making sure there were no vacuum leaks, I cleaned my throttle bodies and the IACV valve. That solved my problem. I thinks it's the IACV valve that gets gummed up and sticks.

I did a write-up on a unique way that I go about cleaning my t/b's and IACV at every oil change. The write-up also includes a link to some info on the effects of carbon deposits on valves It works and smoothes out the idle every time I do it. I use Carb cleaner when I do the cleaning, but the method would also work with Seafoam which a number of other people like to use. The only other way to clean the IACV is to dis-assemble it and clean it by hand.

If you're interested, PM me for a link to the write-up. Or I could post the write-up over here if there was a place for it.

 

did you install the TPS with the right amount of amps? .4 i think?. Also could be your IAVC as stated above. I installed a brand new IAVC but then learned that I should have tried cleaning it first and it took care of my high idel problem. Could also be your water temp sensors or you might just need a ECU reset. Mine was extramly hard to start and found that cheap spark plugs installed by the previous owner was the cause. Also what type of O2 sensors did you install. I put some bosh ones in my dads dodge once and it ran like crap and found out the bosh O2 sensors were not long enough to get an accurate reading. Running fuel injector cleaner can also clog fuel filters. I read a thread on injector cleaner and alot of people said it was bad to use it alot because of this issue. (I used to use it every oil change also)
hope this helps

 

The tps should be .4 volts not amps.
Bad temp sensor usually causes high idle and rich running condition.
Bosch o2's for the Z are just fine. You need to get the correct p/n.
There are only myths about f/i cleaner causing problems. That's a new one on clogging filters. On the one about it damaging injectors, there was a post by a nissan master tech service manager where he stated that in 22 years of working on nissans and Z'zzzz, he's never seen a failure caused by anything except that they just wear out over time.

 

Hey CC, I'd like to post your write-up on my site, if you don't mind: http://www.ttxtz.com. I think I could make a place for it on my Tech page.

 

I send the link to it out after the other site comes up where it's posted.

 

I tried to post the write-up here but there is a limit of 10 pics and the write-up has 13. PM is on the way.

 

split it up between a few posts.