Analyze my aircare printout

[mtharvey]

analyze

http://img218.imageshack.us/my.php?image=img0015zv0.jpg

high hydrocarbons and carbondioxide on driving and idle test

[AudiDude]

analyze

http://img218.imageshack.us/my.php?image=img0015zv0.jpg

high hydrocarbons and carbondioxide on driving and idle test

High hydrocarbons are caused by unburnt fuel. Check your 02 sensors first then your catalytics.

[dealhunting]

Type of car would help......

High HC alone usually indicates a misfire of some sort, but when accompanied by high CO, it shows a rich running engine. Audidude is right, start with testing your O2 for a lazy signal. Was your car at operating temp when you ran through the test?

[mtharvey]

1991 nissan 240sx

Thanks for replies. I dont know how to check catalytics.
I have checked my sparkplugs and they are not wet.
I did a self-diagnostic test with car ecu which suggested my O2 sensor is good. For some reason though, when I disconnect O2 sensor I dont get a fault code on ecu. I dont have ecu bolted to frame of car.

My injectors leaked for a long time so maybe they damaged catayltic converter?

I did a fuel leak test which suggested that my injectors dont leak but maybe my check valve on fuel line leaks.
My fuel pressure slowly goes from 44 psi to 34 psi if engine is not turned on. I can stop loss of pressure by pinching fuel delivery hose at fuel filter. I assume the check valve is leaking.

[D-3vil]

You're really fighting an uphill battle here, as far as emissions are concerned. 240's fail way too often. It's unfortunate, cause the car is very fun to drive.


1991 nissan 240sx

Thanks for replies. I dont know how to check catalytics.
I have checked my sparkplugs and they are not wet.
I did a self-diagnostic test with car ecu which suggested my O2 sensor is good. For some reason though, when I disconnect O2 sensor I dont get a fault code on ecu. I dont have ecu bolted to frame of car.

My injectors leaked for a long time so maybe they damaged catayltic converter?

I did a fuel leak test which suggested that my injectors dont leak but maybe my check valve on fuel line leaks.
My fuel pressure slowly goes from 44 psi to 34 psi if engine is not turned on. I can stop loss of pressure by pinching fuel delivery hose at fuel filter. I assume the check valve is leaking.

[mau108]

I heard before an emissions test, you should take a long ride somewhere to warm up the CAT right before the test.

But as the guy above said, that car is getting very old, if its a 91 you still have to do emissions on it ?

[mtharvey]

1991 is young for a british columbia car. Im guessing it is the catalytic converter. all you have to do is clean iacv and remove aiv and these cars run fine. engines last forever.

[dealhunting]

1991 nissan 240sx

I did a self-diagnostic test with car ecu which suggested my O2 sensor is good. For some reason though, when I disconnect O2 sensor I dont get a fault code on ecu.

My fuel pressure slowly goes from 44 psi to 34 psi if engine is not turned on. I can stop loss of pressure by pinching fuel delivery hose at fuel filter. I assume the check valve is leaking.

It's very unlikely your car's ecu will catch a lazy O2 as EFI was still fairly primative in 91, especially by todays standards. You will have to use either a multimeter or better, a labscope. You want to see a rapid fluctuation in voltage (approx 20-40 times/sec) from 100mV to 900mV with 450mV as a mid-point. Do a google search on o2 testing. I'm sure there's lots of info on the net.

I still say start with your o2 as they will wear out over time.....at the very least ot will gove you a good indication of how your engine is running.

As for your fuel pressure....a 10 psi drop is not unusual after you shut off the car. What you want to see is a residual pressure of at least 15-20psi after 30 minutes. If the pressure drops off to 0 ASAP or fairly soon after you shut off the car then you may have a problem......

This site has fairly good basic info for the DIY...
http://www.autozone.com/repair_info.htm

[mtharvey]

It's very unlikely your car's ecu will catch a lazy O2 as EFI was still fairly primative in 91, especially by todays standards. You will have to use either a multimeter or better, a labscope. You want to see a rapid fluctuation in voltage (approx 20-40 times/sec) from 100mV to 900mV with 450mV as a mid-point. Do a google search on o2 testing. I'm sure there's lots of info on the net.

I still say start with your o2 as they will wear out over time.....at the very least ot will gove you a good indication of how your engine is running.

As for your fuel pressure....a 10 psi drop is not unusual after you shut off the car. What you want to see is a residual pressure of at least 15-20psi after 30 minutes. If the pressure drops off to 0 ASAP or fairly soon after you shut off the car then you may have a problem......

This site has fairly good basic info for the DIY...
http://www.autozone.com/repair_info.htm

Thanks for a knowledgeable answer. My residual pressure is approx 20 psi so Im ok there. The O2 sensor on my car does not monitor O2 under 2000 rpm. That was the way it was designed. SOmething else controls mixture during idle. Since Im failing during idle, it suggests something else is wrong. Im getting a new O2 sensor anyway because it is old. I'll do the voltage test as well. thanks.

[dealhunting]

It seems I may have given you some incorrect info. on most cars your age, the O2 can be tested in the manner I described. ie: the O2 sensor produces it's own voltage once it reaches operating temps. In your car it seems, Nissan used a different approach and therfore must be tested differently. The O2 is supplied a voltage and output is measured as it varies from that 1V. I'm afraid you won't be able to test it very accuratly without some special diagnostic equipment and training...If your car doesn't utilize O2 control at idle, look for some kind of idle switch and or duty cycle adjustment/idle air bypass that will adjust your CO at idle.

Sorry, but I'm not familiar with Nissan's approach to electronic engine control. you may have better luck and information at a Nissan forum....


Exhaust Gas Sensor

The exhaust gas sensor, which is placed in the exhaust pipe, monitors the amount of oxygen in the exhaust gas. The sensor is made of ceramic titania which changes electrical resistance at the ideal air/fuel ratio (14.7:1). The control unit supplies the sensor with approximately 1 volt and takes the output voltage of the sensor depending on its resistance. The oxygen sensor is equipped with a heater to bring it to operating temperature quickly.

[russfest]

Hmm, thats interesting about the O2 sensors being different dealhunting. I would have thought to test it the way you origionally described.

I too think it might be the o2 sensor. Have you ever changed it?
Do you know if it is a HEATED O2 sensor, and if your CAT was hot before testing it? That might make a diff.
I agree that usually you can clean the iacv and tb, then be good to go.

Im from the lower mainland as well with the airscare bs. You showed the graph, what about the numerical side with the info on what the max limits, average vehicle reading, and what yours was. That might give us a better idea.

I would change the O2 first before cropping out and changing the cat. If you do change the sensor, get an aftermarket one with a heater, you just run an extra two wires, one to ground and one from your coil so its power from your ignition.

[mtharvey]

It seems I may have given you some incorrect info. on most cars your age, the O2 can be tested in the manner I described. ie: the O2 sensor produces it's own voltage once it reaches operating temps. In your car it seems, Nissan used a different approach and therfore must be tested differently. The O2 is supplied a voltage and output is measured as it varies from that 1V. I'm afraid you won't be able to test it very accuratly without some special diagnostic equipment and training...If your car doesn't utilize O2 control at idle, look for some kind of idle switch and or duty cycle adjustment/idle air bypass that will adjust your CO at idle.

Sorry, but I'm not familiar with Nissan's approach to electronic engine control. you may have better luck and information at a Nissan forum....


Exhaust Gas Sensor

The exhaust gas sensor, which is placed in the exhaust pipe, monitors the amount of oxygen in the exhaust gas. The sensor is made of ceramic titania which changes electrical resistance at the ideal air/fuel ratio (14.7:1). The control unit supplies the sensor with approximately 1 volt and takes the output voltage of the sensor depending on its resistance. The oxygen sensor is equipped with a heater to bring it to operating temperature quickly.

My car is 1 volt output for rich and 0 volts for lean per factory service manual.(o2 sensor screwed in but electrical lead disconnected) I'm reading a little less than 1 at idle and over 2000 rpm. The voltage starts off low and gradually increases to approx 1 as car heats up.

[mtharvey]

benchmarks:


[img=http://img141.imageshack.us/img141/4977/img0003qk4.th.jpg] (http://img141.imageshack.us/my.php?image=img0003qk4.jpg)


readings during idle:

[img=http://img222.imageshack.us/img222/5015/img0004tb6.th.jpg] (http://img222.imageshack.us/my.php?image=img0004tb6.jpg)

[dealhunting]

My car is 1 volt output for rich and 0 volts for lean per factory service manual.(o2 sensor screwed in but electrical lead disconnected) I'm reading a little less than 1 at idle and over 2000 rpm. The voltage starts off low and gradually increases to approx 1 as car heats up.

That is not an accurate way to test an O2.

By the looks of your test results you failed both idle and cruise and failed BAD. To be honest, if I were you, I would take it into an aircare certified repair facility and get it diagnosed properly. At least this way if repairs exceed your repair limit, you have the choice of not doing it and still get a conditional pass for 1 year.

[mtharvey]

That is not an accurate way to test an O2.

By the looks of your test results you failed both idle and cruise and failed BAD. To be honest, if I were you, I would take it into an aircare certified repair facility and get it diagnosed properly. At least this way if repairs exceed your repair limit, you have the choice of not doing it and still get a conditional pass for 1 year.

I did test O2 sensor with it connected to ecu. I still got around 1 volt during idle and then the the readings starting going crazy .2,.4, .5., .8 volts alternating. The O2 sensor on this car does not control mix during idle so this makes sense.


Going to repair shop tomorrow. will report back.

[mtharvey]

Took it Auto Folks in Langley. they say the main computer is shot. I was not getting codes when I disconnected the the o2 sensor so this makes sense.

They say it passed they dyno test. For some reason, the guy took it through aircare to see if will pass. Says I will need catalytic converter if it does not pass.

They say the aircare test is free so they are obviously created a conflict of interest where they have to sell parts to make money.

[dealhunting]

I did test O2 sensor with it connected to ecu. I still got around 1 volt during idle and then the the readings starting going crazy .2,.4, .5., .8 volts alternating. The O2 sensor on this car does not control mix during idle so this makes sense.


Going to repair shop tomorrow. will report back.

Thats actually how a functional O2 works. Once it reaches operating temp, it normally toggles between 0 to 999mV as it reacts to the amount of oxygen in your exhaust. That is how the ecu "trims" your a/f mixture. The fact that your o2 toggles its full range and not just stay near the higher or lower end of its operating scale, is important. It means your car's ecu is reacting and making changes to your a/f. Even though your o2 may be ignored at idle by your ecu, it should still function is a similar manner. It should never be skwed at either end of the scale.

As for your O2 not coding, it may not on such an old car, it may need to be unplugged for 10 minutes or more or it may need to be driven, as you say the o2 is ignored at idle. It may only give you a rich or lean running condition code, which could mean anything. It's not until the OBDII years that unnplugging an o2 definitly set codes. To make things worse, Japanese OBDI diagnostics were very primitive as compared to its domestic counterparts. In '91, I would have to say GM and Chrysler had way better and accurrate on board diagnositcs that the Japnese did.

There is a cat converter efficiency test/formula that should be used be before replacement. A sample before and after should be taken and have a min 80% efficiency to pass.

http://www.aircare.ca/index.php?repinfo-ere-comptesting-3.php

So did your car end up passing in the end or not?

[mtharvey]

I didnt talk to the mechanic yet but I looked up the results on aircare and it passed easily before they could have put a new converter in. My ecu did throw codes for the o2 sensor when I disconnected it previously.