I cant believe it failed smog

08-09-2012, 04:49 PM
We got the car running great but it failed smog bad.

o2 was fine

then nubbers are for 15 mph and 25mph

HC.... measured 107/115 max allowed 59/34 so that real bad

co%.... 0.37/0.28 max allowed 0.49/0.46 that was barely OK as the average is 0.05

NO.... 1760/263 max allowed 484/498 average is 56/64

any suggestions?


08-09-2012, 05:21 PM
Was the car at normal operating Temp when the test was done?
What < year > < make > < model > ?
How many miles are on the clock?
When was the last Tune up?

08-09-2012, 11:25 PM
1993 Buick Regal
100k miles
new plugs
fuel filter
I have another post here about it running crappy.
We got that sorted out.
And it seemed to be running like a champ.
It was really hot today he drove it 10 miles from his moms house to mine and then to the smog place so I think it was warmed up pretty good.
I didn't go with him because i thought it would pass just fine.


08-10-2012, 09:47 AM
A nice hot car is going to have less emission than a cold one.
If Test's pass when hot, you might consider getting a hotter thermostat.

Tech II
08-10-2012, 10:44 AM
O2 is fine? How do you know? Could have what is known as a "lazy" O2 sensor....the sensor may not set a code, but it may not be swinging between the limits(hovers at 0.452 volts), and not having enough cross counts(not switching rich/lean enough times in a certain time limit).

Another problem with these O2 sensors is, they don't have heaters....during testing, the sensor could cool off, causing the system to go into Open Loop....

Take the vehicle for a good, hard ride...get it warm....and definitely don't shut it off before the test....

08-10-2012, 05:21 PM
O2 levels are fine
The O2 sensors i dont know.

I will most likely change them.

In was looking and there is supposed to be two.

One in the exhaust maniflid and one in b y the cat.


08-10-2012, 06:05 PM
Focus on the H20 sensors closest to the exhaust manifold, it's used for the feed back signal so the ECU/PCU can formulate the air/fuel mix.
There should be one on bank1 & bank2.

08-10-2012, 07:26 PM
Focus on the H20 sensors closest to the exhaust manifold, it's used for the feed back signal so the ECU/PCU can formulate the air/fuel mix.
There should be one on bank1 & bank2.

I think you've been working on too many Fords. :grinno: GM rarely installed O2 sensors in both manifolds.

The OP's car should only have one heated sensor in the back manifold near the firewall. IIRC they didn't start installing downstream (post-cat) sensors in the Regal until 1994.

08-10-2012, 08:28 PM
The oil could be contaminated with gas from the what ever caused the previous performance issue, anyway high HC's are indicative of a misfire or rich mixture, as mentioned the o2 sensor should be looked at for proper switching. 20 year old o2 is way over it's normal life anyway.

08-11-2012, 01:52 AM
I would bet its the o2 because its running so good.
I cant feel any kind of miss in the pedal at all.

I'll check to see if there is two o2's
The book says there is two on the 3.8 but this is a 93 so i'll poke my head down there and check to make sure one way or antoher.
We will change the PCV valve too.

I'll check out the oil and see if it needs changing.
I dont think it does since the problem was a lack of fuel primarily because of the filter.
And when we tested the fuel pump there was no pressure loss after it was shut down. So i dont think there are any leaky injectors.

Thanks for the input/help


Tech II
08-11-2012, 10:00 AM
This is OBD I....so NO O2 after the cat.....should be just one O2 sensor,,,,

08-11-2012, 10:40 AM
My bad, haven't worked on a OBD I system for 18-years.

OBD I system, it might have a bad or dirty Air/Smog pump or check valve.
Is there an air filter on this smog pump?
How about a vacuum hose going to the smog system, or EGR?
How about the belt for the smog pump?

08-16-2012, 10:31 PM
we changed the o2 sensor and drove it around a bit and took it to be retested.
It failed again
http://img856.imageshack.us/img856/1430/img0785jr.th.jpg (http://imageshack.us/photo/my-images/856/img0785jr.jpg/)
http://img10.imageshack.us/img10/8862/img0786pt.th.jpg (http://imageshack.us/photo/my-images/10/img0786pt.jpg/)

Were thinking it might be the cat.
I'm going to look into testing the injectors to see if one is sticking or somthing also.


Over all it was better than before, but still not good enough.


08-19-2012, 01:22 AM
here's the latest

we checked the injectors

4 ohmed out at .015
2 were at .014

so were going to get a coiple at the wreckers and make sure the ohm out to the .015.

And were looking into replacing the cat on it but in calif they want alot of money over $300 to replace it.

I'm going to post another question regarding the CARB cats & a 49 states cat to see which way we want to go.


08-20-2012, 09:09 AM
You might want to do a compression test 1st, before throwing too many parts at it.

It's funny, how California residents can get a license/prescription to smoke dope, but there cars cant.

If the compression is good, it's probably time for a new California catalytic converter too.

See www.converterwarehouse.com (http://www.converterwarehouse.com)

08-20-2012, 12:19 PM
Hang on, don't jump so fast on the cat. If the car passed the smog all these years, it may still be good. In theory, they don't wear out. What usually kills them is bad emissions going in to them. I have a 21 year old Grand Marquis with the original cats and it passes the smog test here well under the limits. And it has 350000 km on it, which translates to about 200000 miles.

Please do some proper diagnosis instead of just throwing parts at it. You will end up replacing lots of parts that don't need replacing. You will want to check engine vacuum, look for leaks, check air filter, O2 sensor, MAF sensor. Some of these can be done with a scantool, although I've never worked on an OBD I GM, just an OBDI Ford. What you cannot check with a scantool, you can probably check with a VOM, like you checked the injectors.

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