Failed smog, high NO, help!
 

I have a 1987 Targa that I don't drive very much. It only has 70,000 miles. Two years ago I barely passed smog with just under the legal limit of NO. Today, my car failed because the NO was just over the legal limit at 25 mph. HC and CO were very low. I drove the car around for at least a half an hour, and it appeared to be well warmed up at the time of the test.

The technician told me to add some octane boost and come back, which I did, but that didn't help. From what I understand this is a symptom of the car running too lean. It looks like I'm going to have to take the car in for some diagnostics and repair, but I thought I would check in here to see if anyone had any suggestions for how to deal with this problem. Thanks in advance.

Where are you in SoCal, Norte or South. If you are in L.A. or O.C. I can adjust it for you :D. Gratis. PM me.

You sure you don't have a vacuum leak? Do the oil cap removal test. Run the car, bring it up to operating temps, leave her on and remove the oil cap, if it does not change, you may have a vacuum leak.

Thanks much for the advice. Unfortunately, I am in San Diego. I will do the oil cap test though, and see if it indicates a vacuum leak.

Smog test aside, how well is the car running ?

I would consider replacing the O2 sensor first. They are cheap.

Well, if you can wait, I will be in Bonsall on the 21st.

It's running hot and/or lean, especially if the HC and CO numbers are super, super low. Intake leak, maybe cooling issue. O2 sensors typically fail rich, as do most other things in Motronic, so those wouldn't necessarily be the first things I'd check.

Fuel supply could be an issue, too -- though again, dribbling injectors tend to cause rich running conditions in my experience.

What's the O2 % reading on your smog test? High numbers there would indicate that your cat is shot.

Post your full smog report.
But I agree with prior post that you are likely running lean. If we see the entire report it could be more helpful.
The solution may be as simple as richening it up a tad via the AFM mixture screw.

Vacuum leaks are pretty common on the 3.2 due to intake manifold gasket failure that will result in high NO due to running lean. If your idle improves when spraying carb cleaner at the base of your manifolds, you might be too lean. If that's the case, take it in and have the CO adjusted and then it should pass.


Cheers,

Joe
87 Carrera that also failed for the same reason, but passed after CO adjustment.

You are very close to passing, you could try richening up the mixture.

EDIT:
I just saw the CO number, you are running lean. A CO of about 0.1 is lambda (AFR of 14.7) and your down at 0.01
I'd get a reputable shop to setup your mixture properly and I bet you'll pass. Or if you have access to a wideband O2 gauge you can set the mixture yourself.
And as Joe pointed out you could have a small vacuum leak somewhere.

OK, here is my smog report.

http://forums.pelicanparts.com/uploa...1454610119.jpg

Below is the second test. The first test was very similar except the NO level at 15 MPH was only 128, with the NO level at 25 MPH was 593. The O2 level appears to be very low.
I'd say the car was pretty hot when the test was done, especially the second test. The temp gauge was above the first tick mark as the car had been idling for a while. When I'm normally driving the car, the temp is about at the first tick mark when fully warmed up.

http://forums.pelicanparts.com/uploa...1454610130.jpg

Overall the car seems to run fine.

Thanks for taking a look!

OK, thank you. I will do the oil cap vacuum leak test this evening. If it's OK, I will have my shop adjust the mixture (I don't have an O2 gauge). The adjustment is basically just the turn of a screw. Is that correct? Hopefully, not too expensive. Hopefully I don't need a new cat...

Thank you! I'll let you know what I find out.

The screw for setting mixture is located on the bottom left corner of the Air Meter, it's a 3mm allen key. Turn it clockwise (in) to richen.

If you are handy with a digital volt meter and have a good one available that can read down below 1volt you can also set mixture with a poor man's approach that works well. Basically you unplug the stock O2 sensor and measure the output voltage the sensor is generating with it unplugged. If you are lean that voltage will be below 0.3vdc and as you richen it it will go above 0.7vdc you basically lean the mixture till voltage drops to <0.3vdc and stop. Then you count turns as you richen it till the meter swings up to >0.7vdc and stop. Then turn the screw back lean 1/2 the number of turns, that's aprox. lambda. PM me if you wish to try or need advice.

The DME will do a lot to compensate for vacuum leaks, or high fuel pressure, etc. It's amazing really.

I think you have a bad cat. Have you recently overfilled the oil? How old is the O2 sensor? Has the distributor failed in the past?

The oil was a bit high last time I changed it, but not too excessive... it's fine now. The O2 sensor is original as far as I know (I've had the car for 10 years, and only put about 10K miles on it).

It does not hurt to replace the O2 sensor. How many miles on the car?

70K on the car.

Make sure the brown wire (bridge to ground) is connected under the driver's seat.

If it's not, then re-connect. Drive the **** out of the car. As in, get it hot, put a lot of load on the motor, etc. Google the term "Italian tune up" and do this. Change the oil, adjust valves, change spark plugs, make sure you use good fresh gas, and take it back in. You might pass. If not then I think you might try to borrow a cat with an O2 sensor bung on it.

70K on the sensor, change it, even if it's working it's sure to be a lazy sensor. Lazy means it's reaction time to change in O2 is significantly slowed compared to a new sensor. This reaction time is important to have a good closed loop O2 mode.

What's the theory here about bridging the brown wires? When you bridge those you retard the timing slightly, this normally elevates exhaust temps. Are you saying to do this to get the cat nice and hot? I'm worried that this approach would elevate NO even more, no?