View Full Version : Emissions Test: It's ok to burn oil eh?

05-28-10, 06:37 PM
This on my 97 STS, 350,000 KM's, ~100,000-120,000 on engine.

Initial Test:

$450 repair limit!

ASM2525 (moving)

HC ppm: Limit 50, reading 143; FAIL
CO%: : Limit 0.28 reading 0.54 FAIL
NO ppm: Limit 365, reading 1091 FAIL

Curble Idle

HC Limit 200 reading 208 FAIL
CO% Limit 1.00 reading 0.91 PASS

Exhaust was smoking blue through the entire test. My car does not normal smoke like that while driving. I had asked them to NOT shut the car off until the test was complete, but they shut it off anyway for 2 minutes before they started. Oh well.

Off to the diagnostics center:


Scan PCM for codes and data: No codes recovered.
Running closed loop
Upstream O2 sensors working good.
Downstream O2 Fluctuates, Monitor reads running lean.
Bank 1 Long term at 1.5%
Bank 2 Long Term at 15%
bank 1 fuel pulse 2.24 Ms
bank 2 Fuel pulse 2.46ms at idle

Excessive ammounts of blue smoke coming from exhaust while engine is running. Owner reports oil consumption of 1L per 1000-2000 km's.

Removed 2 spark plugs: large ammounts of deposits on grounding tip, piston heads are BLACK.

Inspect both PCV and Crankcase vent lines for oil; no oil inside either.

Oil consumption issue is from either rings or valve stem seals.

Air filter was dirty, replaced air filter. No vaccum leaks found.

Perform catalytic converter effinciancy test:

1100RPM under load:

Pre-HC 143, CO .74, NoX 1127
Post HC 137, CO 0.67, NoX 1115

has aftermarket small body converter installed:
converter is not lighting up.

Reccomended repair:

Replace piston rings

Parts: $800
Labour $1870

Inspection $100
Air filter $7.95

Thank you for your business!


Back to the drive test place:

Echaust did not smoke this time :P

Second test:


HC 146/199
CO% 0.51/0.99 (pass on idle :O)
NOppm 1155/N/A

Cost of repair estimate $2670, repair limit $450


so i go get my sticker and now have a June 2011 plate.


After much discussion, we are thinking rings. And im sure i remember a GM TOP cleaning procedure for that exact problem. My car burns oil, the cat is not doing much of anything except clogging up my exhaust. Its a fairly new "supposedly high-flow ill tell you what you want to hear for 200 bucks" cat. Its likely clogged all to hell from burning oil.

So, do i head to the dealer and get a bottle of GM TOP cleaner? Pull out the service manual and follow the procedure myself step by step?

If i do that, what next with the cat? Can oil residue be cleaned from it? I have never had a PCM code for inneficiant catalyst. I can certainly get the cat checked first. 3 options i see are: clean existing cat, get new cat, or remove cat entirely. People already said its bad to remove it, of course. Cleaning it even possible? or i can go get a used cat from a donor car (after checking it first of course). Dont really want to spend that much on a NEW OEM cat...

Well at least i finaly got what i wanted. Ive been trying almost a YEAR to find out why this car doesnt run right, why such a lack of power, seems i may have a tennis ball shoved up the exhaust.

On a lighter note, its not burning coolant :):):)

There is a tiny drip coming from the bottom of the resevoir :(

05-28-10, 09:41 PM
I have not heard too many good things about aftermarket CATs. I'd look for a used OEM CAT if you can find one and install that. Then beat the hell out of it as often as possible with the WOT procedure to try and free up the piston rings. That should reduce your oil consumption and smoking. If you are not familiar with the procedure read up on it in the Technical Archives at the top left of the forum page.

05-28-10, 10:57 PM
I'm well aware of the wide open throttle procedure. This car gets the snot kicked out of it just about on a daily basis. more so since i decided it was on its last legs, and more so since ive repaired all the ABS/traction and suspension code issues. I was quite surprised to hear that there was so much black on the piston tops and that the rings could be stuck. Then i remembered this car ran rich for a few months cause of the bad O2 ground thats since been fixed. Ill have the cat cut and looked at next week, and ill be sure to give it a couple good runs after that if i know its clean. We'll see what those pistons look like after.

I'm thinking if they are still black, a TOP clean might be in order.

05-29-10, 09:53 AM
Keep in mind that there is combustion going on in the cylinder. I would expect them to be black.

05-29-10, 05:18 PM
bank 1 trim at 1.5%
bank 2 trim at 15%

I assume that means bank 2 is running rich, and thats a bad thing, seems like a big difference to me? searching.......

05-29-10, 06:09 PM
Something is way wrong with the Bank 2 fuel/air mixture.

This may well be a bad O2 sensor........what's this O2 sensor ground fix ??? Those sensors have a precision ground (clean air) reference, and any splices, soldering, crimp connectors - anything - in the OEM harness will screw up electrical sensing and F/A ratio correction to/from the PCM.

05-30-10, 11:17 AM
Catalytic convertor all the way. Went through the same problems with a different car in the past. Aftermarket CC was garbage.

There is no such thing as a good, cheap CC.

The fact that your NO is bad, and your EGR is working is proof that your CC is toast.

05-30-10, 10:05 PM
the ground wire for the O2 sensor HEATERS was broken off and i fixed it, not the ground for the actual sensors. Yes the cat is clogged, im just wondering why the huge discrepancy from bank1 and back 2. Also the tech comented somewhere in my previous post about slow umm.... pulse width? on one O2 sensor, but im not sure that means anything.

So far everything i can find and read says we've done all the test we can. There are no identifiable vacuum leaks, etc... I have another intake in the garage with newish injectors that i've been thinking about swapping for a while now....

05-30-10, 11:46 PM
I didn't even mean necessarily clogged. I mean they just don't work worth a damn.

06-01-10, 08:16 AM
If that happened here the inspection stations would be getting audited by the air quality people.
Cars that fail for visible smoke and then pass are put under a microscope.

06-01-10, 08:38 AM
up here they give a conditional pass with the assumption that you will repair the problem or replace the car within 2 years. Yes i would say the inspection station was a bit iffy, i took it to one place who refused to test the car first. I had to "talk" to the owner of the 2nd place just to get them to test and fail the car.

06-03-10, 06:42 AM
Something that may help is a switch to synthetic oil. At the Mazda dealership I work at, we use that trick with the mazda speed 3's and the turbo CX-7's... Due to the turbo, they have overactive PCV systems so they burn excessive amounts of oil.

The synthetic oil does NOT cure the problem; it just burns cleaner with no smoke.

06-03-10, 09:55 AM
I didn't even mean necessarily clogged. I mean they just don't work worth a damn.

Cat is clean. Well, i mean ya its dirty, but you can see through it clear as day. For testing pruposes... i decided to experiment.

"Throw that cat in the river" i said (then i put it in my trunk cause uhh... thats like 80 bucks:)).

So im running catless. No difference whatsoever in how the car runs. It still runs like a bag of sh!t at anything over 10% throttle.

But at least now ive seen living proof how bad these aftermarket cats are for these cars. Look at those pre and post-cat numbers above. And the cat im using is still good!

GREAT cat, for a Cavalier!

Down the list i go... only 2 things left: injectors and fuel pump/filter. Only other thing it could be after that is the tranny... and i know thats on its way out too. 4 tablespoons of clutch material in the pan :P

06-04-10, 09:02 AM
So i pulled the fuel filter today. I blew into the input side (quick connect side / tank side) as hard as i could. Might as well have been trying to put more air into a basketball...... Even tried again after letting it dry for a while, same thing.

Well its getting fuel NOW! I'd like to see those numbers now. My guess is: Bank 2 was adding fuel because of a lean condition, lean condition cause by starving for fuel? Injectors probably dripping too, fuel pressure was very low, hard to start in the mornings. PCM was commanding more fuel but the injectors werent actually supplying it. I was thinking Bank 2 would be starved because thats where the back half of the fuel rail is, but i think im wrong. Pressure is pressure and should be equal from one end of the rail to the other? I dont know, its confusing stuff. At any rate, its running better (harder?) now than it ever has, actually rips through the rpms now, no hesitations. Trans is shot, shifts 1-2 like a 10 speed bike. But at least i learned something, which is what this car was all about :)

06-05-10, 02:02 PM
Bank 1 has #1 cylinder on it, which means it's the rear bank. The forward bank is bank 2.