Failed emissions: High HC and CO during idle. driving test ok

[vancouverbc]

Re: 1991 240sx

HC reading =215 ppm Max allowable=108CO reading=1.57% Max Allowable=.82

They also measured CO2 and O2 during the idle test. CO2 was around 13percent and O2 was around 2 percent.

The driving test measures HC, CO, and NOx. Passed easily. Did better than last year.

My idle is around 750. Had my iacv-aac valve apart for cleaning and adjustment before test. aiv is discarded.
Modified by vancouverbc at 2:39 PM 10/5/2005

[vancouverbc]

I took car to canadian tire today. They said they couldn't fix it and i should go to dealer. They said computer was not monitoring/responding to O2 levels. My ECU is not throwing any codes. It did throw a code when I disconnected the o2 sensor. I ran a ecu self-diagnosis of fuel mixture and i got a blinking light at rpms over 1000 which indicates optimal mix. Under 1000 rpms i did not get blinking light. Wondering if taking out the air injection(PAIR valve) assembly might be causing the problem or maybe the idle air control valve is too tightly or loosely adjusted?

I guess the first candidate would be the iacv solenoid.

Modified by vancouverbc at 7:13 PM 10/7/2005
Modified by vancouverbc at 7:42 PM 10/7/2005

[NISTECH]

Your O2 might be dropping out at idle. With it plugged in check the voltage on it see where it is at during idle. post back

Sorry for missing your initial post. I got wrapped up in some other BS for the last couple days.

[vancouverbc]

Thanks:) Someone mentioned in the forums that the O2 sensor doesn't manage fuel mix during idle on the s13. The garage i went to unplugged the O2 sensor and fed lean and rich signals directly to computer during idle and nothing happened so they told me to go to dealer. Also, The self-diagnosis test for O2 sensor says to only test O2 sensor at 2000 rpm.I'll report back on the voltages.

[vancouverbc]

With the O2 sensor screwed in but the lead disconnected , the voltage started at around .5 Volts and went gradually up to .975 volts as car warmed up. FSM says approx 1 indicated rich mix.

[NISTECH]

That would indicate exactly what the car is doing so the o2 appears to be functioning. It is running rich by your 5 gas readings. You need to start with fuel leak down test. I have put a link in the sitcky in this forum on how to do that. You may have a leaking injector. But only a slight leak at idle. do the test and see if it comes up with anything also check you FP reg vaccum hose for having liquid fuel in it.

Another thing thats really important here is check that ground on your MAF make sure it is under .2 volts drop to ground.

[vancouverbc]

I ended up taking to dealer today and they said 3 of 4 fuel injectors were leaking as you suspected. thanks.