IronsmanMedic

Yes, I'm going through the various - and numerous - threads here about smog related troubles...but as pretty much every thread contains at least one person saying "show us the numbers," I figured it was best to start a new thread and include my numbers right off the bat.

For the record:

1993 4runner 3VZE 6.0 w/ 180k miles

First time (about 2 months ago) I took her to get smogged, the guy wouldn't even run it (audible misfire, so he knew it wouldn't pass). Have put some work into the ol' girl since then (including all new injectors - Flamthrower's - new TPS, new FPR VSV, plugs, wires, dist cap and rotor, etc.).

Finally went in for second attempt at test. Everything checked out, so the truck was run. All inspection components checked out except for timing (16 degrees BTDC). *Didn't notice I didn't have the EGR temp sensor...whatever.

FAILED! CO% is within range. HC (PPM) and NO (PPM) are both too high.

I've gone through this engine and done everything I can find, checked everything (including EGR) I can get to, and she's running really well (well, not according to CA's BS rules) - passing all FSM checks, minus my needing to replace the EGR temp sensor.

I'm attaching a pic of the smog report. I'm going to go back through and check everything exhaust/emissions related, per the FSM...but in the meantime, can any of you smog/emissions geniuses take a look at the numbers and tell me if anything jumps out at you as a "for sure it will be (blank)."?

For whatever it's worth, the tech said my timing being at 16 degrees should have actually helped me (but it didn't). If my numbers had been within range, he would have just entered 10 degrees and passed me, but since the numbers were so far off, he just recorded the actual timing. Based on his statement, putting timing back to 10 degrees will actually make my numbers worse? Will it make my CO increase too?

Also, I have the silicone from the VAFM cover already out (from a recent fix)...the "clicker" is where it was when I took the top off...if adjusting the VAFM a click or two either way will help me pass, I can do that with relative ease (but I'll need to silicone it back together before the retest, since the guy said he wouldn't make a big deal about it today but wants to see it sealed up next time he sees me).

Additionally, could the misfire condition (due to a faulty #5 injector, which has been fixed) that had been going on for who knows how long before I bought the 'runner have caused the CAT to clog, thus ruining what appears (cosmetically) to be a relatively new CAT?

Finally...since the FSM doesn't say anything about checking the CAT (just how to replace it), is there any truth/validity to doing a heat and/or pressure test (comparing pre and post cat numbers), running lacquer thinner through the tank, and/or physically cleaning the cat using liquid laundry detergent?

IronsmanMedic

Just in case it has anything to do with anything, here's a fairly complete list of everything I've done to the 'runner so far...

scope103

not me.
Your HC is high, but your NOx is over the moon! I assume you have the temp sensor replaced with a resistor or something to suppress the CEL. Which means you're now flying blind.

The purpose of the EGR is to limit NOx. That's what it does. That's all it does. The temp sensor checks that the EGR is working. Without the temp sensor, you didn't know that your EGR is NOT working. If it were me, I'd run the FSM diagnostics on the EGR. I'd add checking that the the passage into the plenum is not substantially blocked by "crud." Last, I'd fix the temp sensor so that I'd get the full benefit of the ECU's brilliance, and not have to wait for a smog tech to tell me what I should have already known.

IronsmanMedic

The EGR has passed FSM checks (twice before, and will be tested again tomorrow morning). Although the EGR temp sensor is bad, the EGR itself is less than a year old and, again, passed all FSM steps, as did the EGR vacuum modulator (last checked about a month ago). When I had the plenum off last, to install injectors, I cleaned the plenum and the EGR tube (the one that runs from the EGR valve to the plenum...made it nice and shiney (but it wasn't clogged to begin with, just had some soot and crap on it, but flow was unobstructed.

I don't need the currently out-of-order EGR temp sensor to tell me that the EGR is or isn't working, unless the FSM steps are lying to me and it's not actually working even though it passes all tests. That said, the EGR temp sensor IS on the short list of things to replace, but it was low priority compared to injectors, VAFM, etc. Now with the truck operational (and running relatively well), I can bump the temp sensor back towards the top of the list...

rworegon

With everything you've done, it seems you are down to:
Correct the timing
Missing EGR part
CAT
O2 Sensor

Have long are you running the rig before you take it in? Keeping it running while waiting?

IronsmanMedic

I was afraid of that...

I warmed her up this morning (about 15 mins), THEN left my house and hit the freeway to the smog place (about a 15 minute drive at 50-70mph)...then left it running when I got to the place and proceeded to shoot the sheeeIT with the tech for another 10mins or so about his new Jeep Wrangler before he even began looking at my 'runner. I can't imagine my cat could have been any hotter w/o employing an oxy-acetylene torch.

andykrow

Your tech is a little off I think. Timing too advanced causes high NOx but NOT high HC. My thinking is you're too advanced AND you're running lean.

Lean could cause high NOx and high HC with CO and CO2 fairly normal.

Not sure how Cali works but here in CO we get a free attempt after a fail. I'd get that timing correct and replace the O2 since you're probably due for it (Denso ONLY plus it's cheaper like 50 bucks or so) then run her through.

As for the cat I know my 22re can easily pass emissions with a gutted one as long as it's running right. not sure about that 3.0 in that respect... Just saying in a 22re it wouldn't be the CAUSE of a fail - something else would be malfunctioning as well as the cat.

EDIT... Just remembering as well that my old FJ60 was SUPER sensitive with timing to get all those emissions numbers right. I must have run it through 10 times, and the one that passed was moving the timing only 2 degrees or so. Might be worth trying a run with timing correct to see where you're at before you spend more money.

scope103

This site http://www.autoshop101.com/forms/h56.pdf has a good tutorial on emissions analysis. Based on that article and your low O2 percentages, I don't think you're too lean (too lean will cause high NOx, but not the high HC ... at least until you're so lean that you're misfiring).

Good luck!

andykrow

My understanding (and I surely could be wrong, haha) is that a lean mixture burns slowly, and hence can result in an incomplete combustion giving you higher HC. But good call on the o2 being likely too low to indicate lean.

osv

the path carrying exhaust gas to the egr also has to be clear... i had it blocked off with an aftermarket exhaust gasket, and it failed smog big time.

simple test, you should be able to feel heat from the exhaust, where the egr tube hits the intake plenum.

maybe don't need that tho, because the most basic 22re egr test basically kills the motor at idle; v6 test should be similar.

when you go back in for the re-test, they can do it without hooking up to sacramento, which avoids getting the vehicle labeled as a gross polluter if it fails... unfortunately most of these smog jockeys won't give you much of a price break for doing two tests in a row, assuming the pre-test passes.

i've read that you can use a heat gun to check for the cat being plugged, fwiw.

blake.nemitz

had a similar problem with my 3.0 high nox and stuff. i retarded the timing to zero and it passed with room to spare. ran like crap but passed

Sturmcrow

When I got my truck it would throw the CEL code saying that the EGR temperature sensor was bad. After much troubleshooting, and finally going so far as to start blowing through the vacuum hoses, I found out that the hard line in between the EGR valve and the EGR regulator was plugged up. Cleaned it out with a drill bit, and it has been good to go ever since.

I just passed my first smog test a few weeks ago and barely squeeked by on the HC. I think it may be super rich (based on soot at the tailpipe) so will use that smog analysis link posted above. Thank you to the person that posted it.

IronsmanMedic

All FSM tests (pertaining to actual operation of the EGR valve and vacuum modulator) pass, including the touch test (the tube leading from EGR to the plenum is warm after driving)...except I found something.

I was going through ensuring that all passages were clear, from VSV to EGR, VSV to vacuum modulator, VSV to FPR, etc. The HARDLINE that connects the EGR related VSV to PORT Q of the Vacuum Modulator doesn't allow for any air movement (in either direction). All hardlines look clear, except for the one just mentioned...there's a beige/yellow crusty substance visible at both ends (inside the tube), which I must assume runs the length of that line. For those who are more sensory based, imagine trying to suck down a milkshake through a coffee stirrer.

Compressed air didn't do a damn thing. Any ideas on what I can run the length of the tube (hoping to do this w/o having to pull the plenum off to pull that entire hard line piece off) to unclog it? Only thing I can think of is wire, but I am not wire savvy enough to know what gauge wire I can thread through the line that won't break off within the line itself (obviously stranded wire won't work LOL).

Thoughts anyone?

Also, think this could be the reason why the NO is so high?

P.S. Although the EGR to plenum tube is warm, it's by no means hot, which I assume it should be, considering super-heated exhaust gasses are supposed to be passing through it. I'm guessing it's just being warmed by the radiant heat coming off of the engine during operation.

IronsmanMedic

Unfortunately, here in CA, they only allow +/- 3 degrees from the manufacturer's recommendation, so I have to at least be close to the 10 degrees BTDC. I'll be adjusting the timing to the stock setting and hoping it makes the truck run better, not worse.

blake.nemitz

that might work nox is related to cylinder pressure and advanced timing would do it. if all else fails get a bottle of guaranteed to pass and dump it in

RJR

The ECU possibly knows more about this problem than you are finding out from it so far. You need to make some measurements on the diagnostic port with your multimeter. Do the following and report back with results.
1) First, warm up the engine as you did before your test.
2) Put a multimeter from pin VF1 to E1. Measure the voltage at idle and at 2500 rpm. It should be between 1 and 4 volts. If it's stuck at 0 or stuck at 5V your emission control loop stuck to one side.
3) Shut off the engine, short TE1 to E1, restart the engine, and make the same measurments. (VF1 to E1). If your control loop is working properly and the O2 sensor is healthy, that voltage should cycle between 0 and 5 volts slightly slower than once/second. This will be a bit hard to see on a digital meter, but again, you should be able to tell if it's moving or if the voltage is stuck at 0V or 5V. This voltage is the conditioned O2 sensor output.

If both of these tests check out, and you're sure your EGR system is healthy, then it's likely that your cat converter is bad.

Just to repeat some quick theory on this:
- The cat converter only works effectively to minimize HC, CO, and NO when the air-fuel mixture is stochiometric (~14:1)
- The O2 sensor gives a binary output that tells the ECU whether the mixture is rich or lean, but doesn't tell it by how much.
- The ECU adjusts mixture until it gets an equal number of "lean" and "rich" outputs from the O2 sensor. That tells it the mixture is balanced between rich and lean.
- The cat then does it's job and cleans up the remainder of the emissions.
- As a side operation, the EGR system reduces exhaust gas temperatures enough to eliminate most of the NO production, so that the cat can handle the rest.

scope103

The tests Ron (RJR) describes are good to do, because they are EASY. But I don't think your problem lies there. Having 0 or 5v are the limits of learned fuel trim, but both are valid and your truck should pass smog with either one. If 0 or 5v is not enough to stabilize the O2 sensor, that should throw a code (25 or 26). Similarly, if the O2 sensor is not flipping "about" 8 times in 10 seconds, that too should throw a code. And you don't have codes.

But, because your EGR temp sensor has been disabled, your ECU has been "fooled" into thinking the EGR is working Which you have confirmed is probably not true!

The good news is that according to this page http://personal.utulsa.edu/~nathan-b...77exhaustg.pdf , the VSV works (turning off the EGR) only when the coolant temperature is below 48°C. When the truck is warmed up, vacuum should be passed through the Q-to-EGR valve connection and start the EGR working. So if that hard pipe is blocked, your EGR isn't working, and it's no surprise your NOx is over the moon.

Of course, I would fix it. Some 18 gauge steel wire (any hay baling in your neighbor hood?) would be where I would start.

But, you can just hook the Q port directly to the EGR valve. Since the EGR will be "working" all the time, the engine will probably run poorly until warmed up. But once it's warmed up, I would guess you'll be good to go.

IronsmanMedic

Snaked out that hard line. Haven't run the multimeter tests yet though.

IronsmanMedic

Can someone (anyone) confirm that I should NOT be able to pass air in either direction via the larger tube coming from the bottom of the EGR Vacuum Modulator? I believe it's been referred to in threads as the "backpressure tube" and allegedly there's a diaphragm in this thing that is supposed to prevent any air from actually moving through the modulator itself (any vacuum or air pressure is simply to move the diaphragm), and thus if air does pass all the way through said tube that means the diaphragm is blown out and thus the modulator is bad/needs replacing.

Do I have this all correct?

*If I am correct, I assume this "bad" EGR Vacuum Modulator would be a cause for my "over the moon" NO numbers during the smog test. Yes?

scope103

I can't "confirm" anything, but here's http://www.autoshop101.com/forms/h61.pdf a better drawing of an EGR Modulator. It looks to me like you are correct; if you can blow air through the exhaust port on the bottom of the modulator, the diaphragm is toast and the modulator will be stuck at "I see very low exhaust pressure" all the time.

Since the purpose of the modulator is to provide more EGR during higher load, I would expect you are NOT getting enough EGR, and I would expect that to lead to high NOx numbers.

The good news is that a replacement part is only about $50 http://www.toyotapartsoverstock.com/...ssembly=487700 (RockAuto also has them, but oddly their price is only a little lower than this dealer). I can't say whether this will finally solve your problems, but everything points to a problem in the EGR system, and if you've confirmed a part is bad then I would definitely work in that direction.