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Rebuilt top half of the motor. Valve job, new gaskets, New injectors. everything.
Tested and was a gross polluter.
Then got New Cat, new EGR Modulator, New O2 sensor, New air filter.
Second and 3rd test, everything passes EXCEPT NO reading.
Smog guy believes the low (.01) CO% means it's not getting enough gas, and as gas goes up NO will come down.
What do you all think?
What would you check?
I have a new fuel filter coming as I don't know the last time it was changed, but I can't believe that would restrict flow so much as to cause this issue.
Better to take it to a good test AND repair guy. Throwing money at parts and hoping for a lucky guess not the best idea IMO. That's what I did last fall on my '89 22RE. I was expecting to have to replace the converter, big bucks. Nope. He cleaned up the intake tract and adjusted the tuneup specs including timing and good to go. 13-Aug-2021 Fresno smog system service/re-check $148.00 Adjust timing, clean intake tract, general cleanup of engine/passed OK @Smog X This was not the original test place, so I paid the full test fee on recheck.
Better to take it to a good test AND repair guy. Throwing money at parts and hoping for a lucky guess not the best idea IMO. That's what I did last fall on my '89 22RE. I was expecting to have to replace the converter, big bucks. Nope. He cleaned up the intake tract and adjusted the tuneup specs including timing and good to go. 13-Aug-2021 Fresno smog system service/re-check $148.00 Adjust timing, clean intake tract, general cleanup of engine/passed OK @Smog X This was not the original test place, so I paid the full test fee on recheck.
EDIT: I meant to say took it to the mechanic first. I'll be 77 shortly, and trouble-shooting cars and wrenching has lost its attraction lately...
Do you still have the smog report that was done before the top end rebuild? I'm wondering if there was a big jump in the numbers, and pondering the possibility something got connected wrong during the rebuild. Especially vacuum lines get swapped to the wrong ports. The visual inspection done by most test-only stations is pretty quick and rudimentary. They may spot something disconnected, but I seriously doubt they'd spot something plugged into the wrong port.
No codes... Pretty sure everything is correct with all the vacuum lines.
I don't have numbers from before, I purchased it with a blown head gasket so the first run as a gross polluter is the starting point. New Cat and O2 sensor helped drastically, but still dealing with the NI.
One shopped suggested maybe some EGR lines are clogged? Not sure that would lead to a lean mix though?
No Codes logged.
Last edited by Wouldjaball; Dec 23, 2021 at 08:26 AM.
I'm gonna say this is a case of "a little knowledge is a dangerous thing." To a certain extent, CO combines with NOx in the catalytic converter. So increases in CO emissions can actually reduce NOx emissions, and mask an NOx problem. It is not uncommon to repair a CO emissions problem, and, as a result of a different (EGR?) problem, have NOx increase enough to fail SMOG. http://www.cygnusx1.net/Media/Supra/...taTech/h56.pdf So if you could figure out a way to push up your CO emissions (getting the truck to run rich?), it could knock down your NOx a little. But certainly not enough for you to pass.
Your CO numbers are fine; there really isn't a CO number that is too low. But the EGR system is there to reduce NOx; that's all it does! Your numbers are so high I'm 99% sure your EGR system isn't working. Since you're in California, I'm guessing your have a California truck. It should have an EGR gas temp sensor, which should help your diagnosis by throwing code 71. Is yours a California vehicle? Either way, you'll need to diagnose the EGR system, and the manual is where you start: http://web.archive.org/web/201204061...77exhaustg.pdf
Thanks Scope103 for outlining that. I had doubts about whether or not the CO could be too low, and your view is encouraging.
I don't want to mask the problem, I want to solve it and have the engine running right.
I took the EGR valve off today and let it soak in some valve cleaner.
(It was missing a nut on the back side of the valve, which I'm sure isn't good, but the seal was still pretty tight.)
I also ran an old guitar string thru the metal tubes that run across the front from the EGR valve across the front of the engine as I had heard those can get blocked some times.
The EGR modulator is new, so I'm hoping the valve was dirty and cleaning it solves it.
I have no idea if it's a Cali car or not, is there an easy way to tell? I'm guessing it is, I believe its been in Socal since first sold.
I'd love to hear opinions about whether or not I need to drive the truck a certain amount before testing...
It doesn't have plates, so it hasn't been driven much at all since the head gasket repair.
I know the Cat needs to be hot when going in for the test, but does it need extended highway time just to get everything back to normal?
Having to periodically clean the egr valve of carbon was pretty common, especially for smogging. The vacuum test is pretty easy to do and should give you a very good idea if the egr valve itself is a issue.
You tell if you have a California or Federal vehicle from the under-hood sticker. That sticker is how you manage the vacuum routing, so it's pretty important.
The EGR gas temp sensor is a pencil-sized sensor on the side of the EGR valve. http://web.archive.org/web/201003261...00egrgaste.pdf There's a 2-conductor wire about 5" long to a connector. In a "Federal" vehicle, the valve has the cast boss but it isn't threaded, and there is no sensor. What does it do? The ECM knows when exhaust gas should be going into the intake manifold, so it checks to see if the passage is "warm but not hot." I've never done it myself, but I'm told you can put your hand on the tube and make that same test.
You might consider pulling the EGR tube out of the intake manifold (It's about 12" long). The PCV system puts a lot of "schmutz" into the intake, right at the EGR tube. It's possible you have so much oily carbon in your intake manifold that it's actually blocking the EGR. (If that's the case, it's also blocking some vacuum ports.)
Soaking and guitar strings are all fine, but I gave you the FSM page, so do all the tests Toyota thinks you should do.
Doing burn-outs in the parking lot to get the Catalytic Converter hot, or pouring malt liquor into the gas tank, etc., are all old-wive's tales. Maybe if you have an absolute POS it might nudge the numbers just far enough to barely pass, But notice the difference between AVE and MAX. You can have 5 times the average emissions and still pass. You've got a lot of room; if you're so close to MAX that heating the converter makes any difference, you need to go back to square one.
I had a similar problem with emissions testing documented in this thread. My diagnostic steps are in the replies up to Post #25. You can see my engine setup in my signature so not quite stock but nothing extreme. The solution for me was to unplug the EGR VSV relay, which will cause the EGR to operate all the time. For some reason the ECU was turning off the EGR during the low speed part of the emissions test causing higher NOx readings, leading to a failure. My comment in Post #16 relates where the senior tech at the provincial test center actually told me about disconnecting the EGR VSV relay to pass the test!
According to the FSM, the VSV is actuated by the ECM solely based on coolant temperature (and the manual gives tests to confirm that). The EGR is supposed to be 'off' with a cold engine (otherwise it would run poorly). Your smog test is run with a warm (enough) engine to run the EGR.
jgrant721 could have had a bad ECT sensor, a bad VSV, bad wiring, or (very unlikely) a "confused" ECM. Each of those could have been tested for, but since that wasn't done, we'll never know. There is something attractive about just carefully unplugging a connector (you won't pass if the inspector catches that) and hope for the best; it only costs $75 and an afternoon. You'll need to plug the connector back in (or poor running with a cold engine), and then you'll be back to poisoning all of us. At least run the tests; you'll probably find the problem and know that it has been fixed.
hey so did ya unplug the vsv or go down the rabbit hole of diagnosing possible egr issues? No judgement just curious and cause I'm having the same issue, my last test results HC-.98 CO-13.15 NOX-3.3 and PHX/AZ standards are HC-1.60 CO-20.00 NOX-3.0
Dec 22, 2021 | 05:01 PM
