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

[vancouverbc]

Re: 1991 240sxHC 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.

[hybrid_flyer]

hc= misfireco= mixture

so you have a misfire due to either too much fuel, too little air, or poor spark

[vancouverbc]

I have cleaned out my throttle a few months ago. I also adjusted the calibration screw that determines how open throttle is at rest. I cleaned the idle air control valve . It was very dirty so there was big adjustment to the screw controlled valves that control how much air is allowed in at different points in combustion cycle. I'm guessing the problem is air.

[hybrid_flyer]

well were those readings at idle or at 25 mph

[vancouverbc]

The failed readings were at idle. A 30 second test. They provide a graph.The HC jumped instantly to 162 and then climbed at a constant rate to 215 over the course of the 30 second test. The CO jumped to .70 percent and than increased at a decreasing rate for 10 seconds. after about 10 secondsboth graphs were quite similar. co2 percent was almost flat. O2 shot up instantly to highest percent and than decreased at decreasing rate for rest of 30 seconds.

[hybrid_flyer]

first return all of your idle settings back to what they originally were. then if you have access to a scanner or an oscilloscope, figure out what cylinder it is, from there figure out if its air spark or fuel

[vancouverbc]

ok thanks:) i thought maybe if it only occurred during idle i could narrow it down. i guess i will have to go to pro and get raped real good.

[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 assembly might be causing the problem or maybe the idle air control valve is too tightly or loosely adjusted?
Modified by vancouverbc at 7:19 PM 10/7/2005

[WeldingHank]

replace your O2 sensor. and also check your ECU coolant temp sensor.

[vancouverbc]

replace your O2 sensor. and also check your ECU coolant temp sensor.

they disconnected to O2 sensor and sent in lean and rich signals and the computer did not respond or the idle air control valve is not working properly. or ?
Modified by vancouverbc at 7:21 PM 10/7/2005