Advice on Emissions!!!

[jalterio]

My trusty 1995 legacy is called in for emissions this month. The problem is that my check engine light went on (PO4020) Cataytic converter.

 

I think it might be an O2 sensor, but I am not positive.

 

Will clearing the code (CEL) just prior to bringing it to the test station work? Someone told me that they scan the car and can detect recent resets. Is this true?

[TSiWRX]

^ I honestly do not know how this will apply to older OBD-II vehicles.

 

On newer OBD-II vehicles, resetting/clearing the CEL will wipe out the dash indicator (automatic failure if lit), of course, but it still will not allow the vehicle to pass emissions testing as, more than likely, the sensor you've just reset has not reached "readiness," which can take several full drive-cycles.

 

However, my good musclecar buddy here at work has managed to get several mid-to-late 90s vehicles, both domestic and foreign, to pass Ohio E-Check, OBD-II, via simple resetting of their CELs through his basic scantool, by simply clearing such CELs *immediately* before pulling into the inspection station. It seems, for whatever reason, on these vehicles, no "not ready" state is ever reported by the sensors.

 

I don't know why this is, but honest-to-God, I'm reporting only the facts.

 

With P0420 (did you make a typo?), that's the CEL code thrown for "rear O2 sensor insufficiency."

 

With our '05+ Legacies, upgrading the "plumbing" via an UP and, more commonly, a catless DP (even a shorty) can cause this reading as too much exhaust gas gets metered by the rear O2 sensor, just aft of the third and final cat. To defeat this CEL, aside from going with aftermarket engine-management (which "soft," or electronically, defeats the CEL - i.e. the ECU is reflashed and thus believes that there is no reason to throw the code/light), many of us have gone with using two "stacked" (threaded one into the other), 18mm spark-plug anti-foulers (alternatively called "defoulers"), bored out on the inside so as to be able to accommodate the O2 sensor's width (you can do this even without a drill-press, simple powered hand-drill plus plenty of cutting fluid, such as WD40, will work with a bit of patience), is used to effectively back the O2 sensor out of the main exhaust stream.

 

I'm not sure if this will work for you, as this is a way to circumvent the CEL, but is typically based on a fully-functional third cat and rear O2 sensor - thus....

 

My current questions are:

 

(1) how old is your current cat

 

and

 

(2) is there a way you can get the O2 sensor checked for proper function

 

Best of luck!

[jalterio]

I think it is most likely the Cat converter because it is about 10 years old. I assume because I had purchased this car earlier this year and the MPG and engine idle sounds seem great.

 

 

I would hope it is just a sensor, but the read out for the P04020 read a problem with the Cat according to Autozone.

[TSiWRX]

Oops, I made a mistake - indeed that readout should have read "catalytic converter insufficiency." Sorry, it's my lack of caffeine, yet, this AM. p0420 is a "generic/general" CEL, and indeed, what AutoZone quoted you was correct - catalytic converter insufficiency.

 

However, this CEL can just as well be caused by the O2 sensor being faulty (which is demonstrated by what I cited in the previous post, with our 05+ LGT piping upgrades), if there's a way you can get some readings from the sensor to make sure it's operating properly, that would definitively rule-out at least this cause.

 

But honestly, 10-years is truly about-time for a new cat.

 

A good friend of mine here, locally, is currently experiencing the same problem as you. However, he's already ruled-out both an exahust leak a swell as the need for a new cat, as he's just purchased the latter within the last 700 miles. I'll keep an eye on our local enthusiast Forum to see what resolution he's reached.

 

Best of luck!

[stanjk3]

Had 2 codes when we got the car in Jan, one was for the O2 sensor, other was for the cat. Forget the exact codes, but I cleared them and I haven't had any codes since then.

We only get ~21mpg in "city" driving, I'm assuming that's low for the 2.2L. Idle is a little rough sometimes, but otherwise it runs fine. I don't expect an 11yr old car with 152K miles to exactly purr.

 

Car is due for inspection in Jan, so I'll find out in a couple weeks if it passes emissions. In PA you can get your car inspected as early as 2 months before it expires.

[jalterio]

Did you replace the sensor and the cat at that time? If so, what did that cost you? I get about 25 mpg on my 95 auto, which is not so bad considering the mix driving I do each day to work. I think I may reset the codes and take my chances that it is just the electronic bugs starting up:icon_bigg

[stanjk3]

Nope, but the knock sensor was replaced in Aug when I took it in for a 30K miles service.

[rooski]

A good obd II scanner will monitor the "after cat 0/2 sensor. The voltage should be about .6 volts after full warm up, and should be a straight line. If it follows the "pre cat 0/2 sensors" the cat is not doing the job. You may have to find someone who has access to sub scanner. Hope this helps.

Rooski

[JuxtaGT]

Sounds like the cat is done. Which one is it? Does it have two? My '96 OB finished up the first cat right before I sold it. About 140k miles. They are not cheap in CA. But, my dealer gave me a discount after whinning about not being able to ship OEM parts from another state.

[emyselfandi]

my 95 with 142K has had the same problems. my knock sensor when bad about 40K ago. I kept getting a engine light on the cats about 10K ago. I ended up dropping $250 on a new cat and repalcing it. Light hasn't come on since.

[stanjk3]

I have an Actron CP9135, it doesn't give you real time sensor readings. But at least it gives you what the code means, they make a cheaper version that just displays the code. And of course they make a fancier version that does give you real time sensor readings.

 

New cat was ~$400 including labor, was a direct fit, not a universal one. MPG is still the same so far 19-20.

 

Does the engine computer adjust shift points on the 2G Legacy like it does on the newer ones? And if so is there and easy way to reset it?

[b4wantab]

When you reset the codes the ECM goes into a "testing" mode of some sort. It has to cycle through all sensors a few times, each manufacturer has different loops, before it will give an all clear.

 

If you reset the ECM and then go and get tested they will get a not ready or incomplete reading. Sometimes it takes a few days for the ECM to get through all the cycles. Hope that helps.

 

Peace,

 

Greg

[jalterio]

Thanks all for the replies!

 

-UPDATE......

 

I had checked visually for exhaust leaks (like I can tell right?) and had the code reset the night prior at the local autozone. I took the car the next morning to the testing station and it passed. So with it passing inspection, there is no need to worry that I am doing any additional harm to the environment, right? Or at least legally:icon_neut

[GTsleeper]

no, it will be ok, but before replacing anything take it to a shop or someone with a scan tool(good one that gets data list) have them watch rear o2 function to see what is bad.

[LGTLover]

OK, So now that you are all probly subscribed to this thread.....

I have a similar problem with no CEL.... mine is a 2.5, so it should obviously get worse gas mileage, but i am getting 17-18 in the city. Pretty shitty. I replaced the plugs (before that it was about 14). The car has about 106k on her and she idles pretty smooth. I have noticed that in the mornings if I dont let it warm up a LOT, it sucks down the gas really quick. I also know that if it is not totally warm it will run richer. But it seems to run way too rich so that it almost bogs down the engine below about 3000 rms. At that point it just snaps into shape and goes like its warm!

So, Question #1: I feel like an oxygen sensor is on its way out, but within spec so that it doesnt throw a code. After messing around with the intake and vacuum tubing (which caused the car to stall on its own a few times) the CEL came on for a few starts, but turned off that day. I didnt get a chance to read that code so i dont know if the problem is related or not. But it was definately throwing a lot of gas in the engine while that was happening. So, is one of the sensors "pretty bad" but not "bad" yet? Or is it something else that gives me bad gas mileage and rough mornings?

 

Question #2: How do you know which O2 Sensor it is?

 

Question #3: Could it be the Cat?

 

Thanks so much for any advice you can give me. And if anyone knows where you can find O2 Sensors for cheap, or Japanese ones that have only been used for about 35k, TELL ME WHERE!

thanks again

Nick

[GTsleeper]

1.o2 can work & not throw a code but be very slow on reading the exhaust. Dont replace a o2 with a used one--- thats just stupid. replace with a new & good brand.

vacuum leak,maf sensor, temp sensor(for ecm,not gauge)-- check

if the car bogs-- usually a sign that there isnt enough fuel or a timing, tps sensor is slow, blocked filter, pump is weak, exhaust restriction. if gas is dumping that much- as u say--fuel regulator, injector problem.

I can give ideas but its hard to help when u dont have the car right next to u, dont have a mastertech & data list. really ur best bet is taking it to a good shop.... to at least diagnose it, then fix ur self if ur able to.

2. replace the o2 thats after exhaust manifolds & before cats.

3. yes & no a cat can bog the engine-- if its blocked thats it performance(lack of) wont really change warm or cold. if its loose it might blog flow then not(moved- inside "the cat house").

hope that helps

[ski20inpow]

Similar worries for me. CEL has been on for months now due to pricey faulty cat converters. I borrowed my buddies scanner....shut off the light the night before....went right to emissions in the morning......passed and saved hundereds of dollars. They did not hook up the exhaust or anything.... All they tested was the gas cap for pressure sealing capability. Hope this helps.....good luck

[GTsleeper]

ur lucky, & they wont run exhaust. Thinking about that.....thats messed up!! ive done the same kind of thing on my car. had code, erased, then went to check pending codes on global & nothing! hummm im looking into this.

[pdawg]

Just got mine passed. Unhooked the battery all day Sunday. Hooked it up Monday morning. No CEL. Drove to emmisions. Passed. Pretty easy.

[LGTLover]

why did you have a CEL on? A 2000 leg shouldnt

[GTsleeper]

^ no car should. pdawg must of drove enough to get all drive cycles checked & passed.hmmmm