2 normal spark plugs and 2 carbon fouled

[john]

Will appreciate any help I can get. 85 tercel. approx 140,000 miles on this engine. Passed smog 2 years ago (Calif), with very low emission readings. I had tuned the car , replaced plugs, wires cap and rotor and cat.

Now, 2 years and only 9000 miles later I failed smog. HC and carbon monoxide way off the charts (at east 5 times over). I figured with the low miles I was good to go.

So, today I replaced wires, plugs, cap, rotor, air filter, changed oil. Discovered that #1 plug was badly carbon fouled. I hoped that perhaps that #1 cylinder was not firing very well. Well, after replacing all the mentioned parts I had another smog check. Readings were twice as bad as before I tuned it.

Pulled the plugs, #1 was already carbon fouled after less than 20 miles. #2 was slightly fouled. #3 and 4 looked normal.

Did compression check. #1 170lbs, #2 150 lbs, #3 175 lbs, #4 170 lbs

I suspect carburator problem. The current carb. came from the junk yard in 2005. Is it possible for the toyota carb to deliver too rich a fuel mixture to cylinders #1 and #2 and the proper mixture to cylinders #3 and #4? If so, is there something to adjust? I quit trying to rebuild carbs years ago and have had good luck at the pull it yourself junkyard. They are getting harder to find. Maybe time for a new carb? Other ideas?

Thank you! john

[tercel4wdrules]

Hello and welcome to the forums! We have had members on here that have had trouble passing the CA smog check before (myself included). Do you reside in an enhanced testing area? Also, I hope you weren't getting it through the actual smog test and just having a pre-test done. If you fail the smog check twice as a gross polluter I think at that point you have to get certified at a Gold Shield station or State Referee. That's why on these older cars I prefer just to do a diagnostic and have them run it under manual reading mode.

I would make sure all of the vacuum hoses are properly routed, especially the ones for the vacuum switch 'A' & 'B' as well as the connections for the EBCV (electronic bleed control valve). The EBCV has two hoses that run to the carburetor to adjust the A/F mix during different conditions and under a certain RPM range. It would also be a good idea to replace the O2 sensor if it hasn't already been replaced at some point. I would also inspect and make sure the AAP diaphragm isn't ruptured, which could potentially cause a rich running condition. Have you checked to make sure that the intake/exhaust manifold bolts are torqued properly? These have a tendency of working themselves loose as well. I believe if the engine is running too rich at some point it can cause a rich misfire condition in which the HC levels begin to rise along with the high CO%. You can post your smog test results along with the CO2% & O2% readings and perhaps another member (4wdchico) could give you some advice. Hope this helps some.

[john]

Am in Fresno, an enhanced area. Yesterdays results went to dmv. Todays did not. Have been labeled gross polluter before, hope that doesn't finish off my car. In the past, it has always taken 2 or 3 attempts to pass. Will post the readings tomorrow (they are on my desk at work). Will check the vacuum routing tomorrow. AAP is fine. Will check the bolts and stuff also. thanks for your help. john

[ARCHINSTL]

This is OT, I realize, but what happens if your car is a "gross polluter?"
Many states now have emissions testing only in certain areas - in MO it is only the STL Metro area - but now for '96 and newer vehicles only, as happens in other states as well.
Of course, CA with its climate has a gazillion more old crocks running around and preserved compared to the Midwest and East.
Tom M.

[john]

Smog readings:
10-19-11 (on dyno)
rpm / %co2 / %02 / HC(ppm) / CO % / NO(ppm)
1897 / 9.5 / 2.7 / 5139 / 5.50 / 993
1969 / 9.2 / 2.7 / 5318 / 5.97 / 861

my columns did not line up well. Iwill do this instead:
10-19-11 (on dyno)
at 1969rpm HC was 5139 / CO was 5.97 / NO was 861

10-20-11 after tuneup (not on dyno)
HC was 16742 / CO was 6.1 / NO was 859

test results from 2 years ago:
at 1974rpm HC was 5 / CO was .22 / NO was 17

I checked the manifold bolts that I could reach and they were fine. do not want to pull carb to check under it yet. (checked vacuum and it held steady at 30)

car is idling rough. #1 plug has probably fouled already.

Checked spark - spark jumps 3/4 inch very strong all 4 wires.

Vacuum hoses appear routed fine (they are in the same positions as when I passed smog 2 years ago.

noticed my chilton manuel tells how to check for short in ebcv. will try that.

also shows how to check oxy sensor with volt meter. will do that.

I'm still suspecting carb. Car is definitly to rich at #1 and #2 cylinders

Not sure if I get to do the repairs, or if the State will make me go to a shop. I have always done my own repairs and been retested until I pass. currently I am tested at a test only center.

Forgot to mention: Car is smoking badly for about 1 mile after startup. blue/gray smoke. Is this because #1 and 2 plugs get carbon fouled or do I need new valve guides? Compression is good.

I do appreciate your replies. Wish I found this site years ago.
john

[Petros]

Welcome to the list!

There is no adjustment on the carb that will alter mixture in only 2 of 4 cylinders, the problem is likely somewhere else. I once bought a Tercel that ran like crap cheap. I had two cylinders not making any power (based on pulling spark plug wires one at a time), I was about the pull the head but considered everything that could cause 2 out of 4 to be different. I found the brake booster hose was off (at the brake booster end) and it was making that side of the manifold too lean. I also found 8 other vacuum leaks, ran great after that was fixed.

There is vac operated diaphragm on the carb that if it leaks it will fill the vac lines with fuel. I would guess you have something like that going on, sucking too much fuel into the front half of the manifold.

Good luck

[tercel4wdrules]

After reading the numbers that you posted it looks like a head-scratcher. You're probably dealing with more than one problem. What's really interesting is that despite the fact that it's running rich, NOx output values are also high as well. Usually high amounts of HC is due to a misfire (can be a rich misfire in this case) and both high HC & CO usually point to a faulty carburetor as you have noted. A faulty carb that's running too rich can eventually render the catalytic converter useless as can excessive oil burning as well. Everything works as a system and if there's a fault somewhere, it can bring everything else down with it unfortunately. You don't have another carb you can swap over? Good luck and keep us posted.

[john]

Thank you once again to all.

I tried to see if the EGR system is functioning. The way I do that is to to hold a small screw driver under the valve and rest the tip on the valves membrane. Then I rev the engine and check for movement of the screwdriver. I could not see or feel any movement, but with the rough idle, it is hard to tell. Is there any better way to check EGR?

After the end of the month, I will probably order a carb online. Rebuilt ones seem to be available for around $180. The junk yard ones used to be about $30, but you never no what you will get. Not sure what else to do.

As mentioned earlier, I have a lot of blue smoke on start-up. Smoke is not visible after about a mile of driving. This started gradually about a year ago. I do not know if it is burning oil or could it be from the too rich of a mixture?

Will have to replace the cat, but not until emissions are close to perfect. The one I had put on 2 years ago has a 5 year warranty, but I do not expect that to be honored.
john

[tercel4wdrules]

Perhaps with the engine running that rich and the oil burning, your EGR system might be plugged up. Usually, you can check to see if the EGR is working by applying vacuum to the top vac port and the engine should run very rough or stall. If you don't have a vacuum source to apply, I think you could run a hose from a port on the gas filter (on the intake manifold) and then run a hose to the EGR top vac port and it should be evident whether the valve is working or not. A cursory inspection of the EGR valve orifice and the passages would also be propitious.

A few forum members have bought remanufactured carburetors with good results. I have not purchased a remanufactured one yet, but instead I have had some of mine rebuilt locally, but with mixed results. Do you have any idea what's causing that rough idle?

Blue smoke is definitely oil burning. Perhaps you might have bad valve stem seals? How much oil is it consuming, do you know? You're going to have to solve this oil burning problem before you replace the catalytic converter. You're on the right track with the catalytic converter, that would be the last thing to replace once everything else is squared away. I would also doubt they would honor that warranty, usually the warranty disclaimers state that converter failure due to "overfueling" is not covered.

Please keep us posted...

[dlb]

board member CMB just posted that he is willing to rebuild carbs for $150, plus shipping. i would go with that before i bought another one.

https://tercel4wd.com/forums/viewtopic.php?f=4&t=7013

[john]

Thank you. will consider that. I just pulled the carb and ERG valve. Will probably replace both after the end of this month.

While removing vacuum hoses I noticed that a couple of them had gas in them. One hose attaches to the passenger side bottom front corner of the carb and attaches to the bottom of the TVSV.

There is also a sensor attached to the top of the intake manifold. A vacuum hose leads from this sensor to the TVSV. Another hose leads to the array of metal vacuum lines in front of the TVSV. Both of these hoses had fuel in them along with the sensor. The sensor sits on the intake manifold near the # 1 cylinder intake. Is this part of my "too rich of a mixture" problem at the #1 cylinder? This is the plug that fouls with carbon.

thanks again for responses. john

[ARCHINSTL]

john -
Before buying an EGR valve, whether from a dealer (BIGGA bucks) or a salvage yard, read this:
https://tercel4wd.com/forums/viewtopic.php?f=7&t=1496
Tom M.

[tercel4wdrules]

Thank you. will consider that. I just pulled the carb and ERG valve. Will probably replace both after the end of this month.

While removing vacuum hoses I noticed that a couple of them had gas in them. One hose attaches to the passenger side bottom front corner of the carb and attaches to the bottom of the TVSV.

There is also a sensor attached to the top of the intake manifold. A vacuum hose leads from this sensor to the TVSV. Another hose leads to the array of metal vacuum lines in front of the TVSV. Both of these hoses had fuel in them along with the sensor. The sensor sits on the intake manifold near the # 1 cylinder intake. Is this part of my "too rich of a mixture" problem at the #1 cylinder? This is the plug that fouls with carbon.

thanks again for responses. john

Sounds like you're describing a ruptured AAP (auxiliary acceleration pump) diaphragm. A hose runs from the TVSV "N" port (the very bottom port) to the AAP. I would plug the bottom port on the TVSV and cap off the vac port on the AAP for now until you fix it (but you already removed the carb in this case). The AAP is supposed to aid in providing the additional fuel when the engine is cold to aid driveability, but the TVSV only provides vacuum to this port when the engine coolant is within a certain range, and once the engine is at full operating temp, there's no longer any vacuum provided to the AAP. The sensor on the top of the manifold that you're describing is what Toyota refers to as the "gas filter", which is a doodad that provides manifold vacuum to the EGR system amongst others as well. This means that you will have to buy a carb rebuild kit to source a new AAP diaphragm or buy the diaphragm from Toyota, but the price for this diaphragm if I'm not mistaken is more than what an aftermarket rebuild kit goes for. I have seen several AE82 Toyota Corolla's at the junkyards with fuel coming out of the vacuum lines when I yank them off, so it seems to be that it happens eventually.

Also, is your vacuum advance diaphragm working as well? A bad one will cause a slight vacuum leak and might raise NOx output. When you get the carb worked out I would change the oil as well. You're on the right track to finding a solution to your emissions troubles.

[4wdchico]

I took the California smog tech course. You can do your own repairs. Only a licensed smog tech at licensed station may work on a car that has failed smog.

Petros was very much on the right track.

Check your AAP diaphragm, It is the dome shaped item that is on the passenger side of the carb body, near the right front corner. Pull the vac line off of the nipple on the AAP dome. If it is wet with gas you have found your problem. The auxiliary accelerator pump (AAP) diaphragm fails fairly often and will dump fuel into the vac system and will end up passing thru the "gas filter" that is located on the intake manifold runner to the #1 cylinder. Last I checked 'yota still sold the AAP diaphragm separately. You should also blow out the liquid fuel from the vac system, DO NOT USE COMPRESSED AIR.

You should also check the fuel level in the sight glass on the front of the carb. My guess is that it is OK as your car runs better after it warms up. This would be consistent with a AAP diaphragm failure as the AAP system only has vac applied when the car is warming up, vac is shut off after that. It seems that when the AAP system is flooded with fuel and the car is warmed up extra will still find its way into the intake and make it run rich, just not as bad.

You are off track on your testing the EGR system. Search my posts, I have written plenty on the subject. Most likely EGR problem, and inevitable with high enough mileage, is a vac leak into the intake via the pintle shaft/EGR body clearance becoming worn.

[john]

Thank you for excellent advice. I did not realize what the AAP was. I had checked and tested the wrong valve. There was gas coming out of the vacuum line when I removed it from the AAP.

As mentioned, my current motor produces an awful lot of blue smoke for the first mile.

Is it possible that the extra fuel from the AAP is causing all the smoke, or more likely the valve stem seals?

My engine doesn't warm up past about 1/3. Maybe the low engine temp is also making the rich condition worse.