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Been doing a lot of reading on the site regarding failed emissions and thought it would be better just to start a new thread to ask for help rather than bump an old one. Getting close to my wits end with this smog business so I'm hoping that someone may have had a similar situation and can point me in the right direction. Here is the background:
I've only had this FD for about the last 6 months. It is 100% bone stock (even the precat). It has not been driven much over the last 10 years so I did the following before I dared get it tested:
1) Compression test (~105 Front, ~75 Rear).
2) Changed oil and coolant twice.
3) Drained gas to be safe.
4) Changed fuel filter
5) Changed all silicon hoses and tested all the solenoids. Had to replace a couple.
6) Cleaned/Tested EGR, ACV. Did a quick test on the airpump.
7) Had a look inside the cat. Screen looked clear.
8) Changed wires and plugs.
9) Full tank of 91 gas
Took it for the smog test after a good 30 minute drive on the highway and crossed my fingers. here were the results:
Not too bad right?
So I figured I needed to make a couple small adjustments to take it over the finish line so I did the following.
1) Changed the O2 sensor. This made a huge difference on how the car ran. Much smoother. 3K hesitation was much improved but not fixed
2) Found out I had high oil consumption. Lots of oil in the intake so I switched the turbo assembly with a know good system. So far oil consumption seems normal now. This could have affected HC.
3) Ran seafoam through the system to hopefully clean the injectors a bit.
4) Changed the plugs again. Old ones with 200 miles on them were black. Slightly worse on the rear rotor. I think this was from oil but could be running way too rich from the compression....
5) Ran the tank down and put about a 1/3 of 91 in and added another can of seafoam (was told this could help with HC).
Went to retest and got even worse results:
Now the exhaust does stink like rotten eggs a bit. If my memory serves my old FD was the same except it passed with no issues. I'm leaning towards changing the cat with the Bonez high flow and try again, however the NOX is ok so I'm not sure. . .
What I am worried about that it would be impossible to pass smog with low compression on the rear. For now I do not want to rebuild the engine as it runs fine. No starting issues at all and never comes close to stalling. Quite frankly if I had not done a compression test I would have not known it was that low. The only thing noticeable would be the idle sometimes dips but then recovers really quick.
My plan was just get it to pass now and then over the next year or so rebuild the engine. So I'm looking for some input whether this is a lost cause and just do the rebuild now. It just seems like such an extreme action just to pass the test. I was hoping to enjoy the FD for a while before taking it down for the rebuild.
A good stock cat is what you need for smog. The Bonez might make it worse.
I'd try again without seafoam.
I don't think the compression will make that much of a difference
I am going to assume by the pictures you posted that this is a test on the rollers. We don’t have rollers like that here in Maryland any longer so it’s been some years since I had to deal with that. Chances are it’s nothing you’re doing wrong. A lot of times it’s the person administering the test rolling into boost causing it to jump up like that. Have you verified the air pump is working and factory ecm? I would run the tank down put a couple gallons of the highest grade fuel available with some octane booster and loosen the clamps on the y pipe so you’ll have zero boost when they drive it.
That test is steady state, not an IM240 test where it measures acceleration.
This really looks like an air pump/ACV issue to me. You already changed the o2 sensor. You're consistently low on NOX (low relative to "average" of passing vehicles, per the chart) and high on HC and CO. That means there's not enough oxidation reactions, which is likely not enough fresh air being pumped into the exhaust ports or the cat.
My plan was just get it to pass now and then over the next year or so rebuild the engine. So I'm looking for some input whether this is a lost cause and just do the rebuild now. It just seems like such an extreme action just to pass the test. I was hoping to enjoy the FD for a while before taking it down for the rebuild.
Thanks for reading this far!
ive seen worse pass, there is something else going on besides the engine. it might be worth checking for codes, i wonder about the coolant temp sensor, but i have to say i would have suggested the O2 sensor...
Of course I could be wrong, but I'm guessing you're to the left of the window in the chart below, based on what your test results indicate. The root causes of that are typically O2 Sensor, and air pump, assuming there isn't some other major mechanical issue with the vehicle. Your car is stock and should have CEL illuminate if there are some dead sensors (unplugged etc). However OBD 1 is not very smart, and it mostly only knows whether stuff is unplugged, rather than if the sensors are "working" but inaccurate.
Of course I could be wrong, but I'm guessing you're to the left of the window in the chart below, based on what your test results indicate. The root causes of that are typically O2 Sensor, and air pump, assuming there isn't some other major mechanical issue with the vehicle. Your car is stock and should have CEL illuminate if there are some dead sensors (unplugged etc). However OBD 1 is not very smart, and it mostly only knows whether stuff is unplugged, rather than if the sensors are "working" but inaccurate.
agreed, it can be there for a bunch of reasons, but if the air pump is good that is usually enough if the O2 is good.
my miata has high NOX's and after a really long time i found that it was the PCV valve...
That test is steady state, not an IM240 test where it measures acceleration.
I noticed the 15 mph and 25 mph on the left side.
I agree it’s likely not enough air getting to the exhaust ports. The acv round screen that’s sandwiched under the acv itself I’ve seen clogged with junk not allowing air to get by. The ecu wouldn’t know any better. It’s pain to get at tho.
I agree it’s likely not enough air getting to the exhaust ports. The acv round screen that’s sandwiched under the acv itself I’ve seen clogged with junk not allowing air to get by. The ecu wouldn’t know any better. It’s pain to get at tho.
~ GW
Thanks for all the input. When I changed the vacuum lines I did clean up the ACV. I can't actually remember if I tested it at the same time. Looking at the FSM I can do more thorough testing on the airpump as well to ensure it is pumping enough air.
I'll remove the UIM and take another look. Once this is resolved I will definitely post the solution so we have a record of it on the site.
ive seen worse pass, there is something else going on besides the engine. it might be worth checking for codes, i wonder about the coolant temp sensor, but i have to say i would have suggested the O2 sensor...
That's good to know. I was really beginning to think I would have no choice but to build the engine now. At least now I can focus on the air injection. Hopefully something will turn up there, otherwise I think that only leaves me with the cat. For CA there is only a magnaflow cat that is CARB legal. Only issue is that it would have to be welded in...
That's good to know. I was really beginning to think I would have no choice but to build the engine now. At least now I can focus on the air injection. Hopefully something will turn up there, otherwise I think that only leaves me with the cat. For CA there is only a magnaflow cat that is CARB legal. Only issue is that it would have to be welded in...
the stock cat is basically bulletproof, and the air injection makes it so the cat is less important than it would be on most cars.
I've only had this FD for about the last 6 months. It is 100% bone stock (even the precat). It has not been driven much over the last 10 years so I did the following before I dared get it tested:
2) Found out I had high oil consumption. Lots of oil in the intake so I switched the turbo assembly with a know good system. So far oil consumption seems normal now. This could have affected HC.
I was wondering what happened to that car...can't believe it got away
For the smog, double check the AC fuse in the engine bay and check the voltage at the connector
I checked the air pump wiring and operation and found it was working fine. All checks in the FSM passed and it pumping out plenty of air.
Next on to the ACV. Found the air relief valve was completely carboned up and not moving. The switching valve was moving but had a lot of carbon as well. Disassembled both and cleaned. I thought I had checked this before when I did the vacuum lines but I guess I skipped the ACV...
Car is running much smoothly and the spotty idle I mentioned before seems to have been cleared (Will confirm after a few more drives). The smell of the exhaust is much better as I don't detect the rotten egg smell anymore. Not sure when I will have time to get it smogged but when I do I will post the results here. Thanks for all your help in pointing me in the right direction. This community is the best!
The results are in and it passed! Here are the numbers:
So cleaning the ACV was critical to get it to pass the test. Also no seafoam in the gas...
Just to summarize for future searches. Low compression cars can pass emissions in California. In my case the rear rotor was a bit low and front rotor was fine (~75/~105). As long as all the emissions equipment is in place/working and the car fully tuned up you should be fine. The only part I could not really test was the cat. Just did a visual inside to make sure the screen is clear. The combination of a tired cat and lower compression might make it impossible to pass.
Another point to consider. The tech did mention that some of these Bosch replacement O2 sensors might not work very well compared to OEM. Not sure if there is any truth to that but my CO2 numbers are much higher than my previous FD.
The results are in and it passed! Here are the numbers:
So cleaning the ACV was critical to get it to pass the test. Also no seafoam in the gas...
Just to summarize for future searches. Low compression cars can pass emissions in California. In my case the rear rotor was a bit low and front rotor was fine (~75/~105). As long as all the emissions equipment is in place/working and the car fully tuned up you should be fine. The only part I could not really test was the cat. Just did a visual inside to make sure the screen is clear. The combination of a tired cat and lower compression might make it impossible to pass.
Another point to consider. The tech did mention that some of these Bosch replacement O2 sensors might not work very well compared to OEM. Not sure if there is any truth to that but my CO2 numbers are much higher than my previous FD.
Nice job!! I’m sure you feel relieved. My stock FD didn’t pass CA emission last year, either. Luckily for me, it was just a bad O2 sensor.
The results are in and it passed! Here are the numbers:
So cleaning the ACV was critical to get it to pass the test. Also no seafoam in the gas...
Just to summarize for future searches. Low compression cars can pass emissions in California. In my case the rear rotor was a bit low and front rotor was fine (~75/~105). As long as all the emissions equipment is in place/working and the car fully tuned up you should be fine. The only part I could not really test was the cat. Just did a visual inside to make sure the screen is clear. The combination of a tired cat and lower compression might make it impossible to pass.
Another point to consider. The tech did mention that some of these Bosch replacement O2 sensors might not work very well compared to OEM. Not sure if there is any truth to that but my CO2 numbers are much higher than my previous FD.
The fact that your 15 and 25mph CO concentration is higher than average, and your NOX is lower than average (again, average of passing vehicles), tells me that it's still running a bit rich. That could be caused by the O2 sensor. It's also possible the cat is losing a bit of efficiency. You passed though, and could probably pass for a few more years hopefully with the existing equipment.
The tech did mention that some of these Bosch replacement O2 sensors might not work very well compared to OEM. Not sure if there is any truth to that but my CO2 numbers are much higher than my previous FD.
i've seen this as well. the Bosch stuff just doesn't do very well on these cars. next time
The results are in and it passed! Here are the numbers:
So cleaning the ACV was critical to get it to pass the test. Also no seafoam in the gas...
Just to summarize for future searches. Low compression cars can pass emissions in California. In my case the rear rotor was a bit low and front rotor was fine (~75/~105). As long as all the emissions equipment is in place/working and the car fully tuned up you should be fine. The only part I could not really test was the cat. Just did a visual inside to make sure the screen is clear. The combination of a tired cat and lower compression might make it impossible to pass.
Another point to consider. The tech did mention that some of these Bosch replacement O2 sensors might not work very well compared to OEM. Not sure if there is any truth to that but my CO2 numbers are much higher than my previous FD.
Glad to hear it. The discussion on FB was rather gloomy.
Glad to hear it. The discussion on FB was rather gloomy.
It's a huge relief that it passed. Since I don't drive it much I should be good in 2 years as well. I am also getting organized to build the engine so that should put any emissions issues to bed. On FB I was looking for where to bring it for testing as opposed to technical advice and ended up being a bit of both. The technical expertise on this forum is incredible. I don't think there is a single issue with our cars that can't be hashed out here.
The shop I've been going to for the last 5 years does not like rotaries and even went so far to tell me to sell it and move on as it would never pass. He also said the same thing 2 years ago with my previous FD with 39K miles and was shocked when it passed with flying colors... So I switched shops as the tech was more positive on getting it to pass as opposed to being negative from the start.
I am also getting organized to build the engine so
you might take the car on a long drive, where it can run nicely and be up to temp for a while and compression test it. its weird but how well the car runs can effect the compression test.
It's a huge relief that it passed. Since I don't drive it much I should be good in 2 years as well. I am also getting organized to build the engine so that should put any emissions issues to bed. On FB I was looking for where to bring it for testing as opposed to technical advice and ended up being a bit of both. The technical expertise on this forum is incredible. I don't think there is a single issue with our cars that can't be hashed out here.
The shop I've been going to for the last 5 years does not like rotaries and even went so far to tell me to sell it and move on as it would never pass. He also said the same thing 2 years ago with my previous FD with 39K miles and was shocked when it passed with flying colors... So I switched shops as the tech was more positive on getting it to pass as opposed to being negative from the start.
Well FB is FB, you know how it is. FB Groups have become a lot more popular than old school forums like this, but the format of an FB group is not conducive to technical discussion. It's designed for the user experience and discussion to meet FB's business objectives, as we all know. We don't have to have a discussion about it, but I'm not surprised you had that experience.
In our case here on this forum, you have a group of owners with a lot of accumulated experience who have learned a lot of stuff by trying different things. And specifically here with passing emissions, I am literally an OEM emissions engineer who does tailpipe emission testing and development for a living. I've also written detailed articles on this forum about how the FD emission control and turbo control systems work. So I know what the results mean in the specific context of an FD, and have been able to help multiple users pass emissions by looking at the actual technical details of the test results.
You'll find similar examples where life and career experiences have enhanced the contributions of forum members. Maybe someone has a background in fabrication, or sourcing parts, or worked for Mazda at one point, or whatever else. You gotta stick together to keep the community strong.
12-20-21, 01:01 PM
CA smog help
