Thread: Help with misfiring W10 92 SE-R. Won't idle, misfires 24/7

Iac is bolted to the intake manifold so I guess its after the turbo? It's not even really an idle issue, its just running rich and misfiring. I tried rewiring the MAF today and regrounding it and it made no difference. I noticed my O2 sensor is reading 320 mV all the time and is going back and forth from lean to rich. I'm going to try swapping the coolant temp sensor and O2 sensor next. I've got no idea what is wrong at this point so I guess I'll start throwing parts at it. I really need Nissan Data Scan and some help.

I dont think you're understanding, there is a hose under the throttle body, that feeds air to the air regulator and the idle air control valve, where is it going to?
P.S.
Cleaned the throttle body yet? It also appeared that you have the outlaw spacers, and that you've used RTV to seal the intake manifold...I personaly dont like RTV on the intake, the seals that are there are meant tobe installed dry.

Obviously, if closing the iacv with the modis cured the problem, then your problem lies in the iacv. If your iacv is stuck either open or closed it will cause problems. If it is stuck in the open position, you will be constantly bringing in more air to raise your idle, think of it as a monster vac leak. If it is stuck closed it will not be bringing in any air at all, meaning that if you turn any or all of your accessories on or even put the car in gear and drive, then the iacv will not be able to adjust for the load on the motor. So, my advice to you is to pull the iacv and see if it is functioning the way it is supposed to. The modis would be a great way to test if it's opening and closing properly. If it is working properly, then your wiring is fine and you have a problem with your settings in the ecu. I haven't fooled with the RT's much but in a standalone system you can activate or deactivate the iacv.

So, you have left out lots of info as well, when the valve was open 95-100% what was the RPMS at?

The voltages on the O2 sensor should be fluctuating with the lean/rich. I have seen O2 sensors, mainly on GMs, cause a misfire. I have even seen them cause a stalling condition. Just an FYI.

Well, that pic was used as a reference, it's not actually my motor. Axle missing, no starter, etc.

RPMs were bouncing between 750 - 950, but when I closed the IAC it idled right at 800-850. Now that I have played with timing, cleaned and swapped the IAC and air regulator, and rewired the MAF, that little closing the IAC trick doesn't work anymore. Idle will drop to about 600 and it will barely run. Possibly because I retarded the timing too much, I'm not sure.

Can you explain this more or show me a pic?



Seems like a O2 sensor reading rich most of the time might tell the computer to open the IACV to compensate. The car is still running rich as hell so maybe it can't compensate enough. An O2 sensor is like $40, right? Might as well replace it cause I have no idea how many miles are on mine.

5/8 hose if you're looking directly at the tb is right lower side of the plenum.

i was having the same problem but cleaned the mainfold of carbon build up out etc found a vaccum leak and changed leads and now runs mint and make sure your fuel filter is round the right way as it can choke it from getting enough fuel and cause it to miss etc