FAILED Cali Smog test...

[johnathan1]

All emissions equipment is in place, and the car runs perfect...but it failed the emissions portion of the test... results are as follows:

----------%CO2-%O2----HC (PPM)-------CO (%)---------NO (PPM)
TEST RPM MEAS MEAS MAX/ GP/MEAS MAX/ GP / MEAS MAX/ GP/MEAS

15MPH 1614 11.6 0.0 106 / 281 / 217 0.70 / 2.20 / 5.05 762 / 1949 / 106

25MPH 2647 12.8 0.0 81 / 231 / 140 0.57 / 2.07 / 3.29 701 / 1749 / 301


I'm not positive as to why it failed...but I think my o2 sensor wiring might be bad, and the ECU isn't receiving a signal, or it is intermittent...because at the last smog test, it failed, and the tech bypassed the connector, and it passed beautifully. It looks like it's running too rich...what could cause this? Thanks.

 

[RazoE]

might be old 02 sensor wires..

mine was running pig rich, and would miss when shifting when cold..

replaced the whole thing and now she runs fine...

 

[johnathan1]

Whole engine wiring harness?

 

[RazoE]

no, just the plug and wires...

 

[Big Wang Bandit]

My burgundy car passed misserably the first time.

Then the smog tech rolled it for a while, and got the cat ever HOTTER than the 20 minuite drive there made it, and it passed with flying colors.

Get it REALLY hot

 

[Rennat]

When you get there just leave the car idling... i did that with my eclipse, it was the OEM cat too... haha

but a new o2 sensor never hurts... or just clean it off and shit.

 

[johnathan1]

I've replaced the o2 sensor with a Bosch replacement 3 times. But I would keep getting a code 21, and CEL occasionally. So this time I went back to the OEM o2 sensor that the car passed with originally. I did the o2 sensor inspection outlined in the TSRM, and I get a constant 3.5V between Vf and E1...whether the o2 is connected or not...so im assuming that there is a short somewhere in the wiring harness... :\ I pulled back some of the shielding on the signal wire to the o2 sensor, and it is all green and corroded for several inches...

I am going to bypass the entire engine wiring harness, and go straight from the o2 sensor to the firewall. Hopefully that will do that trick. In the meantime, I will save up for a new wiring harness... :\

 

[johnathan1]

Well, my suspicion has been confirmed. The wiring to the o2 sensor is bad. I bypassed the harness, and wired it straight to the ECU, and now it is cross-counting between Vf and E1 as it should. So I took it back in for a smog retest.

It still didn't pass, but the numbers are WAY different now. The HC and Co are down, but the NoX is WAY up there. I'm not sure why, the smog tech said it could be a clogged EGR valve?

Here are the results:

-------------%CO2-%O2----HC (PPM)-------CO (%)---------NO (PPM)
TEST RPM MEAS MEAS MAX/AVE/ MEAS MAX/ AVE / MEAS MAX/ AVE/ MEAS

15MPH 1674 15.1 0.1 106 / 31 / 9 0.70 / 0.10 / 0.01 762 / 237 / 1328

25MPH 2634 14.9 0.2 81 / 20 / 7 0.57 / 0.09 / 0.00 701 / 199 / 931

 

[935motorsports]

EGR Passage is either clogged, or the EGR is not opening at all.

Check vacuum to the EGR valve under part throttle.

Check EGR passage into intake manifold for "gunk".

 

[johnathan1]

Thanks 935. So is that the ONLY thing that will cause high NoX output?

 

[935motorsports]

That is not the ONLY reason, but the likely one.


Going through many different supras, I have to smog many times a year. Here are the reasons for failure, in the order of most common:

- No vacuum to EGR
- EGR passage clogged
- O2 sensor not working OR wire not connected (broken harness)
- Bad cat



It is 99% of the time these things. With 7Ms, I usually find no vacuum to the EGR. Bypass the EGR vsv and run a straight line to EGR pipe and it should start opening properly.

 

[3p141592654]

EGR is almost certainly the issue now.

In your first test you were running very rich (12.5:1 for the 15mph and 13.3:1 for the 25mph). The second test you are right on the money with 14.8:1 average.

 

[johnathan1]

Alright, I took it in and had it tested for the third time, after bypassing the EGR VSV (wasn't functioning) and just ran manifold vacuum straight to the EGR Modulator (not sure if that would cause a problem). Well this time, the car half-passed the test. It passed the 25MPH test, but not the 15MPH.

I just installed a fully functioning EGR VSV to replace the old one...would this allow me to pass the next test? Or does the valve just open when the car reaches operating temp?

Here are the test results. So close!!!

 

[jetjock]

I wouldn't exactly call twice the cut point close.

All the valve does is disable EGR at certain times, none of which occur during the conditions under which the test is performed. Therefore installing a new one is the same as bypassing it and will not effect test results. You have other problems. I'm guessing insufficient EGR flow from either a clogged passage or faulty modulation. I say that because although the 25 mph passed it's still higher than what I'm used to seeing on these cars and, as you can see from the report, higher than state average.

Unlike the first test your engine is now in fuel control. The cat is also working well. Prior to that you had a classic case of high CO suppressing NOx. Makes me wonder how long you drove it like that. Rich mixtures are what crap up EGR passages. Think about that next time someone tells you narrow band displays are worthless light shows.

 

[jdub]

The EGR VSV will not help in this case. The VSV only functions above ~4000 RPM to shut off the EGR valve...at idle, vac is removed mechanically by throttle plate position in the TB. The VSV does need to be replaced (you don't want the EGR functioning at high RPM).

It looks like your EGR valve is sticking, clogged up, or the channel in the intake manifold from the fitting to the internal opening below the TB is choked off with carbon deposits. JJ suggested in another thread to use a drill and a piece of wire rope frayed on the end to clean the channel. I would try that 1st. Take a look at the EGR vac modulator too. If you do have to clean/replace the EGR valve, it's a royal PITA.

Edit: JJ beat me to it :biglaugh:

 

[jetjock]

Never thought to mention this before but I installed a short piece of .250 SS tubing into the top of the intake manifold fitting. Sticks up next to the brake booster hose. Lets me inject solvent into either the manifold passage or, by using a hand pump to open the EGR valve, into the valve itself and cooler. It's handy for testing actual EGR flow too. Also lets me introduce things like water or CC/valve cleaners into the engine and have them evenly dispersed to each cylinder.

 

[johnathan1]

Yes, I'm still dealing with this problem... (I don't drive the Supra much at all, and I'm pretty busy). Anyway, I replaced the EGR valve with a good used one. While I had the EGR valve off, I looked into the passages, etc, and it didn't really look all that dirty...maybe a little bit of carbon on the passage walls, but it definitely isn't clogged... So I put it back together, and tested the EGR valve by applying engine vacuum. At first it stumbled, and then slowly died. So I took it for another smog test, and it failed the 15MPH NoX portion again, but it's much lower this time.

NoX: Max: 762 Meas: 982

It's really close now, but I'm not sure what to do to get it down the last 200... :[ The tech suggested spraying carb cleaner into a vac line with the engine running at 2500RPM for a while. :\

 

[figgie]

Jonathon

did you check the ENTIRE EGR system.

You said you checked the valve but the EGR valve gathers it exhaust gas from the #6 exhaust port and routes it through the back of the head. You will need to clean that out also.

Carb or water as JetJock mentioned. You might have higher than usual compression inside the cylinder head due to all the carbon buildup while you were running rich. And believe me. I have seen so much carbon build ups on some of these motors the piston is non-exitant visually. And no amount of carb-cleaner or water dissolved it. Only way it came off, Attack with a wire brush attached to a drill.

 

[SirLoki]

so you only get high nox at low speed and then it goes away on the higher speed test?

i had a similar problem with my starlet where my nox were fine at low speed but were way off the charts at higher speed. Turned out my distributor was not working properly at higher speeds like it was suppose to, causing it to run lean producing higher nox. I simply bought a new distributor with vacuum actuator and all is well. Somehow maybe your car is running a little lean at low speed then it richens up as you go faster. Can you confirm your injectors are not clogged or not spraying as well as they should be at idle or low speeds? also maybe you might wanna try a 1 step colder spark plug.