Cooter272

Hey gang. I have a 1998 C5 coupe with 151K miles on it and failed the CA SMOG test today. The car has never failed until now. It failed the visual because the PCV hose at the back of the engine was actually torn and broken completely, so basically not even connected.

The tech ran it anyway and it also failed due to high NOx at 15MPH. He said its possible the broken PCV hose has created a lean condition and therefore led to high NOx.

I already have a new PCV hose and PCV valve on order but would hate to install those and take it back only to fail again. I guess Im wondering if the high NOx condition could indeed very likely be due to the broken PCV hose or if something else might be at play.

Ive never had a car fail SMOG before and don't know what happens if it keeps failing. I guess Id have to find some sort of SMOG repair facility so they can check it out but Id like to avoid it.

Attached are photos of the broken PCV hose and the test numbers. Notice the very low HC and CO numbers. Ive read this may indicate a lean condition as well, furthering the theory of all this being caused by the broken hose.

Should I just replace the PCV and hose, maybe get one of those "guaranteed to pass additives" and give it another shot?

PS...I did run it on the freeway for about 20 minutes before testing.

Thoughts? Thanks!

Cooter272

Thanks for the quick reply!

There was no check engine light on. Here are the codes. I don't think I see anything emissions related.

10 PCM - no codes
28 TCS - C1221H, C1222H
40 BCM - no codes
60 IPC - no codes
80 RADIO - no codes
99 HVAC - no codes
A0 LDCM - U1064H
A1 RDCM - U1064H
A6 SCM - no codes
B0 RFA - no codes

Cooter272

I just fired it up. It idled horribly but then I remembered it is because I have the PCV and hose removed from the car.

I checked the codes real quick anyway but no change, all the same codes as when engine was off.

Cooter272

Bump for the day for any ideas and thoughts.

Would the level of fuel in the gas tank have anything to do with the high NOx? The DIC estimates only 60 miles left on the tank so it is certainly not very full.

Thanks everyone!

Bill Curlee

Clear All of those old DTCs. All they will do is confuse you. Your car has been running poorly so long that the Long Term Fuel Trims (LTFTs) are way out of whack and the Idle setting is also probably way off because it was compensating for the extra air that the engine was getting.

The PCM will self adjust the LTFTs and the PCM will relearn the new idle position after a few minutes of running. Once it relearns the correct LTFTs and Idle position, it should be running a LOT better.

Like you stated previously,, This is the FIRST time its failed. If it were me, I would be checking ALL the other rubber hoses and fittings for ROT.

Bill

Cooter272

I did check the rest of the hoses and they all look great. Previous owner had a lot of the hoses recently replaced, all but this PCV hose apparently.

So my plan of action is to install the new PCV hose and new PCV valve, hopefully they arrive in the mail tomorrow. Before starting the car, I will clear all the DTC codes.

This should then let the PCM readjust the idle and LTFTs after a few minutes of running. Hopefully this works.

One question though, Ive read a few things about having to drive the car for a while after clearing the codes before going to SMOG again, because the tech can see that codes were recently cleared and kind of gives a red flag. Know anything about this and if so, how long I need to drive it before taking it back to SMOG?

Thank you for clarifying the fuel level thing. Maybe no DTCs because of what Bill mentioned, it has been running this way so long that its has compensated for it and just thinks all is normal? Who knows!

Cooter272

Thanks! I was just finishing my reply to Bill about that. Any idea how long it needs to be driven before taking it back to SMOG? Should I just drive it to work a couple days and call it good?

What if I don't clear the codes? Sounds like the codes are unrelated to the issue anyway. Maybe I can leave the codes, replace the PCV hose and valve, drive the car for 20 minutes so the PCM can readjust and then take it to SMOG. Then I can clear the codes after SMOG is done.

Cooter272

Ok. I think I will leave the codes then, since they seem unrelated to the emissions issue anyway. I can clear them once I pass SMOG.

Ill put the new hose and valve on, drive it for a bit to let idle and LTFTs adjust, then give it another go.

Bill Curlee

Oh,,,,, I agree 100%
If your going back to the emissions right away,,, DO NOT clear the DTCs. As long as they are not CURRENT and not P series DTCs,, You will be good to go.

If you go to Autozone, they use the ACTRON Scanner. It will display the status of the EMISSIONS READY AND OR NOT READY FLAGS.

If you have any emissions NOT ready flags it may not pass. Some states will allow one NOT ready flag.

Bill

Bill

Caveboy

I had a clogged air pump that caused the high nox issue

VGLNTE1

Ugh....California...gross

rodsvet

At least obumer isn't from here and the weather is fantastic!! But then, we have Jerry Moombeam Brown and he thinks an imaginary bullet train is more important than water. Go figure! Rod

Cooter272

Disappointing Update:

Installed new PCV hose and valve, still failed the SMOG test due to high NOx. HC and CO numbers are still low but again failed the NOx at 15MPH. In fact it actually went up 8 points since the first test, although the NOx at 25MPH went down.

Attached and highlighted is the latest test with the failed result. As a comparison, I have also attached the results from a passed test taken last year. Notice in the passed test last year the HC and CO numbers are much higher than the recent tests, although still within passing range. Not sure what that means though.

Im at a loss on what to do. Maybe the car wasnt driven long enough after replacing the PCV hose and valve. I think Im going to take it to a SMOG repair shop and see what they say.

SVT_Z06

Change your oil, change your spark plugs and air filter. Then, put some e85 1 gallon or 1 cup of rubbing alcohol in the tank 1/2 full. Make sure you get it nice and hot and drive it to the smog shop and leave it running while waiting.

SVT_Z06

Denatured alcohol works too.

Passed several times using this method. I live in San Diego.

Don't worry about damaging anything. One use will not hurt anything.

Good luck.

Cooter272

Thanks for the tip on rubbing alcohol. I may try that on the next test.

Ive been reading a lot about a dirty MAF sensor causing high NOx. The dirty sensor reads the incoming air incorrectly and causes a lean condition, which equal mores heat and more NOx. Does anyone have any thought or experience with this?

I removed the MAF and cleaned the sensor with the proper MAF cleaner. The sensor was definitely dirty and Im assuming it was due to the oiled K&N air filter. Along with cleaning the MAF, I also installed a new regular paper air filter.

Im also wondering if I didn't drive the car around long enough after replacing the PCV hose and valve in order to give the PCM enough time to readjust. I figured a few minutes would readjust it but I drove it about 30 miles anyway. That is when I still failed though.

Now that the PCV system is fixed, MAF is clean and new air filter is installed, Im going to drive it to work tomorrow and then try smogging again Tuesday. Maybe Ill throw a cup of rubbing alcohol in the tank too. Hopefully this gives enough time to reset and takes care of the problem.

Trios

If it were me, I'd disconnect the battery and leave it disconnected for 20 minutes or so to completely reset the computer. The computer has learned bad values for idle and fuel trims, so you need to reset those back to default, which should be much closer to optimal than what it's been learning.

Then I'd go for a drive, some on the highway, some on some back roads, and then hit a parts store to check the emissions status and only once it shows ready would I go in for a re-test.

SVT_Z06

Alternatively, pulling fuses 16 and 23 will reset fuel trims.

Just an fyi, most, if not all cars will pass with two incomplete drive cycle monitors.

Cooter272

Ive been leery of doing this because I wasn't sure how long it would take for the PCM to be "emissions ready" again.

SVT...are you thinking that a couple of drive cycles (cold start to operating temp), such as going to work in the morning and coming home in the evening, maybe for two days, might be enough to be emissions ready again after pulling the fuses?

Bubbletop409

The rat bastard also thinks illegals are more important than citizens.