Need Help Passing Emissions

[Bohman731]

Hey guys, I am hoping I can get some help figuring this out. I have a 93 NA and I took it to get the emissions done but got a fail.



Here is a video with the car warmed up showing the random idle misfire I am assuming has to do with why I am failing.




The hi flow cats are new.
Ohm tested all injectors and they are within spec.
Used the cheap cigar trick to check for vacuum leaks.
Cleaned the MAF and air filter.
New fuel filter.
New spark plugs.
Checked connectors for corrosion.


That video I posted is after all that stuff was done. So I am figuring I need to get this misfire figured out before I go get a retest and don't know what to try next without just throwing parts at it.

A couple things I feel I should note. The car, until about two months ago, had been parked in my garage for about a year because of a coolant leak. Finally got some time to fix that and in the process I did a plenum pull but I made sure to use an OEM Nissan Gasket and torqued the plenum back down following the FSM. It had the same gas in the tank during that time so I put a bunch of fresh premium in.

Where should I go from here?

[amc49]

Fix the misfire, HC goes up like a rocket with it happening. If that type has plug wires change them, you often flaw them by changing the plugs.

[itsa300zx]

I had a similar idle fluctuation, changed just about very sensor(Coolant, TPS, MAF, IACV, used "Good" O2 sensors, OEM plugs, coils, even ECU, EFI harness only has 20K so connectors are still clean).
Finally fixed the problem with new Bosch OEM o2 sensors.

[amc49]

The first O2 if enough miles on it can cause it, they slowly poison if the driver does not help them do it faster and driving long term missing will do that as well as kill the cat.

[DCaff300ZX]

I had a similar idle fluctuation, changed just about very sensor(Coolant, TPS, MAF, IACV, used "Good" O2 sensors, OEM plugs, coils, even ECU, EFI harness only has 20K so connectors are still clean).
Finally fixed the problem with new Bosch OEM o2 sensors.

Agreed, be sure to replace the O2's with new as intermittent O2's are common and cause the issues you mention, among many other things unfortunately.
The fsm has a bunch of tests and such to help determine the problem as well.

[Bohman731]

So is that where you guys think I should start? Installing new 02's and go from there?

[DCaff300ZX]

So is that where you guys think I should start? Installing new 02's and go from there?

Personally, when I had these issues many years ago with my first Z32 it was time to learn the car (if I intended to keep it long term) and how to fix it, which meant for me to learn the in's and out's of the car. This means using the fsm and testing to find the problems and fix them, as well as troubleshoot the entire car which will obviously be an issue as time moves on.
The fsm is the best way to go about repairs as it's full of the tests and repair procedures that mechanics use professionally repairing these vehicles, going about Z32 repairs any other way can be expensive (random part replacement) and confusing.

In your case it's pretty certain that the O2's aren't up to par and should be replaced most likely, but there is a test in the fsm to determine the health of O2's so I'd be sure there is an issue there first before replacement, and I'd go over the whole thing through the fsm to determine what is needed and how to do it.
Any questions or issues that come up as you do this will be easier for us to answer in order to help you, otherwise it's only best guesses.

[Z31toZ32]

http://www.300zx-twinturbo.com/tech/co/co.html

[DCaff300ZX]

http://www.300zx-twinturbo.com/tech/co/co.html

Although this may "work" to get past an emissions test, you will not fix your car which does need fixing and will get worse as time passes and I'd only recommend this as an emergency fix to keep working, etc.
The fsm and other sources at tt.net and elsewhere will help find your issues and to fix your car, just it will take time and effort on your part. And again, a great time to learn about your car if you intend to keep it long term.

[Bohman731]

So is that where you guys think I should start? Installing new 02's and go from there?

Personally, when I had these issues many years ago with my first Z32 it was time to learn the car (if I intended to keep it long term) and how to fix it, which meant for me to learn the in's and out's of the car. This means using the fsm and testing to find the problems and fix them, as well as troubleshoot the entire car which will obviously be an issue as time moves on.
The fsm is the best way to go about repairs as it's full of the tests and repair procedures that mechanics use professionally repairing these vehicles, going about Z32 repairs any other way can be expensive (random part replacement) and confusing.

In your case it's pretty certain that the O2's aren't up to par and should be replaced most likely, but there is a test in the fsm to determine the health of O2's so I'd be sure there is an issue there first before replacement, and I'd go over the whole thing through the fsm to determine what is needed and how to do it.
Any questions or issues that come up as you do this will be easier for us to answer in order to help you, otherwise it's only best guesses.

Update! I pulled codes (first time) and it gave me the code for the left 02 sensor. I ordered a new Bosch 02 and should have it tomorrow. In the mean time I have the old one soaking with PB blaster so hopefully its a LITTLE easier to get out.

[itsa300zx]

Should always do the O2 sensors in pairs. If one has died, the other WILL fail soon too.

[DCaff300ZX]

Should always do the O2 sensors in pairs. If one has died, the other WILL fail soon too.

^^^^This.
Just another of the "perks" of having a Z32, many items in pairs...

[Bohman731]

Thanks for the help guys. Got another one on the way.

[Bohman731]

Alright so I changed the 02 sensors and that got rid of the code (no codes now) but I still have the stumble issue.

I found this article and I'm down to #7 so far http://www.zhome.com/ZCMnL/PICS/hesitat ... ation.html

Changed the PCV valves since they were cheap and relatively easy to change. I didnt change the hoses though. Is using that article a good plan of attack to nail it down?