Has it been two years already--Failed Smog this time

[2mbb]

Well I was on a pretty good roll and I thought this time I was setting myself up for success. In another thread I cover some acitivities I'm doing to spruce up the old girl. But when I went down to my local test-only smog check place, I did not leave smiling .

Below are my test results, the most current at the bottom. I'm showing all the records I have because I have some questions about the AI system. I went in on May 2, 2024 and failed both speeds (Dyno test) for HC and CO. I had just rebuilt my carburetor, so I pulled the top plate off and discovered that I had installed the 1st and 2nd slow jets in the wrong location. With that corrected I took a second test on May 10, 2024. HC is not passing but my CO is still high. Also my O2 levels are <1 for both speeds, so I am suspecting the AI system.

I failed tail pipe emissions before in 2002. I did a bunch of stuff, but it wasn't until I replaced the AI pump and the Catalytic Convertor, that I passed. In 2009, that rebuilt pump installed in 2002 siezed, and I installed my original pump (to me) which I had rebuilt. My AI pump is not making any noises and my power steering pump is not leaking onto the AI pump.

 

[2mbb]

...continuing...

After my second failure, I started focusing on the AI system. I'm going through the tests and I am having a few problems with some...

"Check ABV Test": When I do this test from the emissions manual I do not get any air being discharged from the ABV. However, when I do the next test, "Check OC Thermo Sensor", I do get air discharged from the air bypass hose. I can also apply vacuum to the ABV upper port and see that the ABV port strokes, so I think that is OK.

The other tests (sections 4 through 8) test OK. With the first round of tests it is only test 5 that doesn't work.

I made a "replica" of the SST 09258-14010 to test the AI pump discharge. My "oriface" was 7/32", so just a little larger than the 5.5mm specified. I found another referece that indicates the "green" zone on the SST gauges is 2.1psi minimum. The discharge pressure of my installed pump was just about at that minimum (I was hoping for something a little higher). I have another pump on the shelf so I installed that one but the results are about the same. So I would say this test is border line, unless someone can confirm what a reasonable output pressure is at 1200 rpm.

I'll have to come back to this later tonight or tormorrow. But I'm interested in any comments or suggestions so far. Thanks.

 

[OSS]

@Spike Strip

I never needed to mess with air pump troubleshooting because (admittedly) I would remove it between tests and install an idler pulley, so it was essentially a brand new pump during every test.

My O2 numbers (with essentially a new pump) were always above 2.0 and my CO was always zero or 0.01

 

[Spike Strip]

FWIW, I struggled for years with low to zero O2 numbers and failed smog even with a freshly rebuilt pump that barely put out the minimum, and I have the SST shown above to measure. It wasn't until I had another pump rebuilt by BZ (that I installed in frustration) that made the O2 number rise dramatically. There was a noticeable difference even with the 'hand feel' of the amount of air discharge between the two pumps.

Those above parameters were written for 1985 gas and emissions testing, so who knows how modern RFG and stricter testing have affected it.

It's been a while since I've studied this crap, but IIRC, the VSV-2, when you burp the engine causes a momentary low-vac for the decel switch which triggers the VSV2 to 'break' vacuum to the top chamber of the ABV, allowing the plunger to fall and divert pump air to the Exhaust pipe to aid the CAT in digesting unburned HC.

When this isn't working , higher HC and CO and sometimes backfire.

I check for this working by watching my A/F meter go momentarily very lean when I burp the engine.

Looking at your above chart (that's a great way to keep track!) you can see your O2 numbers have gradually deteriorated to the point it's now causing you trouble. Oxygenated gasoline greatly effects those numbers, too.

Computer working properly? Check valves ok? Vacuum switch working?

 

[2mbb]

FWIW, I struggled for years with low to zero O2 numbers and failed smog even with a freshly rebuilt pump that barely put out the minimum, and I have the SST shown above to measure. It wasn't until I had another pump rebuilt by BZ (that I installed in frustration) that made the O2 number rise dramatically. There was a noticeable difference even with the 'hand feel' of the amount of air discharge between the two pumps.

Those above parameters were written for 1985 gas and emissions testing, so who knows how modern RFG and stricter testing have affected it.

It's been a while since I've studied this crap, but IIRC, the VSV-2, when you burp the engine causes a momentary low-vac for the decel switch which triggers the VSV2 to 'break' vacuum to the top chamber of the ABV, allowing the plunger to fall and divert pump air to the Exhaust pipe to aid the CAT in digesting unburned HC.

When this isn't working , higher HC and CO and sometimes backfire.

I check for this working by watching my A/F meter go momentarily very lean when I burp the engine.

Looking at your above chart (that's a great way to keep track!) you can see your O2 numbers have gradually deteriorated to the point it's now causing you trouble. Oxygenated gasoline greatly effects those numbers, too.

Computer working properly? Check valves ok? Vacuum switch working?

Thanks, Spike. Unfortunately, I don't remember the status of my "spare pump". I know I got one rebuilt in 2002 by a complany in SoCal called Moto-Parts. I don't think they are in business anymore. At least by 2009 Moto-Parts was no longer rebuilding the toyota air pumps. I installed that moto-parts air pump in 2009 and have been running it since. Since then I've only put about 25K miles on the thing, I don't remember the origin of the "spare" pump I had in a box on the shelf. It looks like it was newly rebuilt but I probably purchased one at a parts store from Cardone or similar.

I did notice that my residual O2 levels have been on the decline, too. I guess I will take the one previously rebuilt by Moto-parts and send it to B-Z. I'll call them today to get a quote.

 

[2mbb]

To continue my story:

I have gone through most of the other tests of the AI systems components with no failures:

• Air Pump: pressure is borderline OK, as noted above
• ACV: Tests for ABV and ASV are OK. I can't develop the pressure with my AI pump to confirm opening of the relief valve. I have removed it and will try to get it to open with my compressed air.
• VTV: I need to check this today
• Check Valves: these seem to be OK, but there is a bit of pressure required to open them (by mouth). If I can figure out a way to test the relief valve opening pressure, then I will use it on the check valves too.
• VSV1 & VSV2: These are OK
• Thermosensor: I did pass the first round test to confirm air is bypassed when the thermosensor is shorted out. And air is not normally discharged from the ABV. but I will check the resistance across the sensor today.

I don't know if my computer is working correctly. I'm think how I might test the various conditions of the table below. One of my stumbling blocks is the vehicle speed input--my speed sensor seems to be working based on the first round test. but I don't have a signal generator to simulate that. I may have to take my testing on the road at least for the one condition that requires Above 50mph.

Yesterday I did crack the housing of my ACV valve assembly trying to get the thing apart . So I am in the process of sourcing another one and seeing if I can fix what I have. I broke off a piece along the crack and I think I may have some success with JB weld.

I'm not sure what other folks have experienced, but I was unable to remove the vacuum operators from the valve assembly. I guess I can squirt brake cleaner in all the air passages, but I do have an ultrasonic cleaner that I like to use when I can (I was happy with the result when I cleaned my carburetor). Should I try putting my ACV into the ultrasonic cleaner? With the orientation of the ASV and ABV vacuum operators, I think one or both would have to be submerged.

 

[Spike Strip]

** What size Ultra-Sonic cleaner do you use for Carb? I've been thinking of getting one since the available carb dip in Kalif is now crap and $40 / gal. Are you able to completely submerge the large pieces? **

The ABV/ACV assemblies seem pretty robust, probably be ok in the Ultra S cleaner, using a mild water-based solvent. AFAIK, the main thing that happens with those assemblies is chunks of stuff get trapped and block movement of the plunger/valves. If they fully open/close with vacuum, you should be good with a simple cleaning.

The Thermosensor won't affect smog numbers, I only have mine for visual inspection though no tech has ever even looked or asked about it. Even when the original CAT was there and TS was missing. Particularly if you now have an aftermarket CAT like a Magnaflow which has much less precious metals and are far less restrictive.

 

[2mbb]

I have a rather small ultrasonic cleaner—2 liters. I had to rotate the carb body pieces to clean all surfaces. Will have to do the same with the air valve assembly if I go that route. I did take off the two removable nozzles and put them through a cycle.

The ultrasonic cleaner works pretty good. Besides using cleaner or degreaser solutions I have also used Evaporust on appropriate parts. That works great for derusting!

 

[2mbb]

Since my air pump was producing what I think is close to the minimum out put (2.1 psi at 1200 RPM), I sent it to B-Z Rebuilders. And a few days later, I did get it back. It looks great and feels good when I turn it over by hand and it is installed back in my truck. I haven't run it with the engine yet because I'm still sorting out my ACV valve assembly. I was a little concerned when I saw the insert from B-Z. It says they bench test the pressure to be minimum 2.1psi @ 1950 rpm . I'm keeping my fingers crossed the rebuild will help.

I did figure out how to separate the ABV vacuum diaphragm from the ACV body. The ABV valve seat is a loose disc that is sandwiched between two ACV body parts. I think now I can put both pieces into my ultrasonic cleaner without having to submerge either vacuum diaphragm. In the picture below the seat is misaligned which should allow me to clean on either side and on the contact areas between the body parts and the seat. There are paper gaskets on either side (you can see the one on the ABV side. Hopefully this will survive the ultrasonic cleaning. I'll try this first on my cracked valve body before I attempt it on the replacement one I got.

I did test my original relief valve and found that the break open pressure is a little too low. it is supposed to open between 5.7 and 8.5 psi, but mine is starting to leak by at around 3psi. The replacement one I got with the ACV assembly I sourced is OK, so that will be used going forward.

 

[jeremyg]

"Check ABV Test": When I do this test from the emissions manual I do not get any air being discharged from the ABV. However, when I do the next test, "Check OC Thermo Sensor", I do get air discharged from the air bypass hose. I can also apply vacuum to the ABV upper port and see that the ABV port strokes, so I think that is OK.

View attachment 3635696

The other tests (sections 4 through 8) test OK. With the first round of tests it is only test 5 that doesn't work.

I had the same experience with this Check ABV test after installing my BZ rebuilt smog pump. The pump is definitely working, and the ABV operates when you create a full vacuum, but I didn’t get “air discharged momentarily” after revving the engine (up to about 2500RPM for me, then quickly letting off the pedal). I’m measuring this by hand feel rather than a sensor, which is good enough for all the other tests I tried, don’t know why it would be different here.

I moved forward assuming this is fine, at least for smog purposes. I think the smog tests are essentially at steady state (low and high RPM) so I don’t think this momentary discharge after the throttle closes will affect the smog test? I’m assuming it’s discharging additional air into the exhaust to compensate for the momentarily too-rich fuel mixture for the split second when you transition from high RPM to no throttle?

Do you think failing this test points to a bigger issue @2mbb ? Sounds like you think it might be your computer failure but I don’t think we could pass all the other tests and the VSV checks without a functioning computer…

 

[2mbb]

I had the same experience with this Check ABV test after installing my BZ rebuilt smog pump. The pump is definitely working, and the ABV operates when you create a full vacuum, but I didn’t get “air discharged momentarily” after revving the engine (up to about 2500RPM for me, then quickly letting off the pedal). I’m measuring this by hand feel rather than a sensor, which is good enough for all the other tests I tried, don’t know why it would be different here.

I moved forward assuming this is fine, at least for smog purposes. I think the smog tests are essentially at steady state (low and high RPM) so I don’t think this momentary discharge after the throttle closes will affect the smog test? I’m assuming it’s discharging additional air into the exhaust to compensate for the momentarily too-rich fuel mixture for the split second when you transition from high RPM to no throttle?

Do you think failing this test points to a bigger issue @2mbb ? Sounds like you think it might be your computer failure but I don’t think we could pass all the other tests and the VSV checks without a functioning computer…

I removed the ACV assembly checked the components individually as best I can (ABV, ASV & Relief valve). I think my ABV and ASV are OK, but my relief valve seems to be opening too soon. In the process of taking it apart, I cracked the housing, so now I have sourced a used one (with a better relief valve) and will clean it up, install it back in the truck and test it. I'm going to simulate the four conditions shown in the emissions manual. I think I can simulate much of the tests either manually or when the truck is parked. Hopefully I can also try and determine whether the computer is working properly. I've got some family stuff to do the next week or so, but when I can get something done this topic I will post up.

Failing that ABV test in the emissions manual may not be important for me. When I am passing smog and have tried that test, I still couldn't get it to work. Also, with the test I can't get the ABV into "bypass to air cleaner" mode. I think my symptoms of low residual O2 would correlate better with being stuck in bypass mode.

Since your original pump was gutted, the new pump will make a substantial difference!

 

[OSS]

Yes I’ve read of guys diverting all the air pump air directly to the exhaust pipe, as if in high speed mode, just by swapping a vacuum hose on the ABV assembly- and then their O2 numbers got really good and their CO numbers then passed.
All that extra oxygen fed to the cat let’s it do it’s job of converting CO to CO2.

 

[Spike Strip]

The above does work, provided the tech is unfamiliar with these trucks.

 

[2mbb]

I went in for my 3rd smog test and failed again!!!

Since the test on 5/10 I have:

• sent my AI pump to BZ Rebuilders and had it rebuilt
• replaced my original ACV assembly with a used one. The used one has been cleaned up and on the bench seems to be operating properly. My old AI relief valve seemed to be leaking through at any pressure and the replacement seems to hold pressure to somewhere around the desired break open pressure
• I disassembled and reassembled my carburetor. Everything seems to be correct. (see below for more carburetor fun).
• I did the lean drop mixture adjustment. The engine seems to be running great, but the tailpipe test says otherwise...
• I did the most current smog test today (6/22) and got the results shown on the last line of the table above.

Any suggestions?

I guess I'll go through the AI tests again just to make sure everything is still "ok". I have another carburetor. I may try to put that on, but I would like to find someone who would measure my tail pipe emissions without actually running the official smog check. Right now I'm going to a test only station. Anyone have any recommendation around Walnut Creek, CA (94598)?

When I was taking my carburetor apart this last time, the retainer broke that holds the accelerator pump check ball in place. Apparently this is one carburetor part of few that is still available. I purchased 3!

 

[OSS]

At least compared to my 2F smog tests, your O2 is still very low compared to mine.
At 15mph, my O2 was 3.3%
At 25mph my O2 was 2.8%

Only way to get more O2 into the tailpipe is with the air injection system. If there’s not enough oxygen, the catalytic converter can’t do its job very well.

After saying all that … I can’t say that a more robust air injection system will allow the engine to pass, it’s just that your O2 numbers stood out from mine and caught my attention. I’m far from being a pro smog technician.

 

[garfieldthecat]

I have not delved into my smog system yet to contribute anything regarding the emissions system components, but could it be that there is a carbon build up somewhere that is contributing to the high HC & CO values?

Although the forum linked here is with regard to fuel-injected vehicles, I wonder if the chart in the discussion is of any value:

What could cause high HC and CO, but low NO and CO2 in a smog test

Despite my confidence in having a (relatively) new catalytic converter and a new O2 sensor, my lovely 1994 BMW 325i Convertible got flagged as a "Gross Polluter." The test results are summarized be...

mechanics.stackexchange.com

 

[Spike Strip]

Gotta get the O2 number up. Or, go in with a few gallons of E-85 next test.

Pump the tires up to 45 psi for the Dyno test.

You verified the AI check valves are functional?

I know you've got the new Air Rail, but verified no leaks?

Verified the metal spaghetti vac tubes are not clogged? (I spray carb cleaner through them and look for squirt out the other side).

 

[2mbb]

At least compared to my 2F smog tests, your O2 is still very low compared to mine.
At 15mph, my O2 was 3.3%
At 25mph my O2 was 2.8%

Only way to get more O2 into the tailpipe is with the air injection system. If there’s not enough oxygen, the catalytic converter can’t do its job very well.

After saying all that … I can’t say that a more robust air injection system will allow the engine to pass, it’s just that your O2 numbers stood out from mine and caught my attention. I’m far from being a pro smog technician.

Gotta get the O2 number up. Or, go in with a few gallons of E-85 next test.

Pump the tires up to 45 psi for the Dyno test.

You verified the AI check valves are functional?

I know you've got the new Air Rail, but verified no leaks?

Verified the metal spaghetti vac tubes are not clogged? (I spray carb cleaner through them and look for squirt out the other side).

I'll go back through and check again for operational issues:

• newly rebuilt AI pump. I have a DIY capacity tool simulating the SST. at the stated RPM (1200) it barely puts out 2 psi pressure. This does seem low. The instructions that came with the pump said that break in period is 500 miles. Would this mean I have to put 500 miles (~10 hours) on it before it will pump to its full capacity? @Spike Strip you mentioned you have the toyota SST to test the AI pump capacity. Can you post a picture of the gauge?
• The check valves do open when I blow through them. But there is some resistance.
• I did put on a different relief valve because my original one seemed to be leaking through at too low a pressure. I will try to figure out how to tell if air is leaking past the ASV (routed back to the air cleaning). Besides potential relief and ASV leaks any air coming out of the AI pump should make it into the exhaust.
• I do have a second AI pump which is also newly rebuilt. But this has a similar capacity as the one currently installed on the truck.

At what point do I turn my attention to the Cat? Is there a way to tell it's working? Can I measure the temperature after running on the freeway for a while?

I'll keep at it. Thanks.

 

[MarkMarine]

I don’t have great domain knowledge to add to this, but I’ve been in a similar situation with other problems and what I hear from this whole thread is:
You had problems with the air pump before. A good pump rebuilt by a good shop fixed it.

You basically looked at this part and it’s connected parts the entire time troubleshooting this new problem. The smog system has a bunch of interconnected components, I think you went deep on this one component because it tripped you up last time, to the detriment of solving the whole problem. Look at the rest of the system. Pretend you never learned about the air pump issue and start from ground truth. It’s an old vehicle and I would really doubt it if the last thing you fixed was the thing broken this time.

 

[Spike Strip]