Topic: Confusing Smog Numbers

[Plekto]

So I went in to get my truck smogged today and here's the numbers:

2nd gear, 15mph, 1641 rpm
3rd gear, 25mph 1752 rpm

Raw numbers 15/25mph:
CO2 14.9/14.7 (pass)
O2 0.1/0.0 (2 year old cat converter) (pass by a mile)
HC 101/99 (pass)
CO 0.32/0.54(expected to be slightly worse with more speed) (pass by a mile here)
NO 1840/737

WTH is going on?  Even my mechanic is stumped as the only thing different is 2nd vs 3rd gear, and all of the other numbers are 50-60% of max except for this one rogue value.   I don't understand why the numbers are so close and this one value is miles off.   All I can think of is that the tech shifted wrong between 1st and 2nd gear?    Yes, I did all of the other things I needed to do - oil change, air filter, checked distributor and plugs and all of that.

EDIT - specs on the truck are: 1987 4Runner.  4 Cylinder, EFI.  Pretty much a bog-standard setup. 

[emsvitil]

Needs some backpressure for the EGR valve to work.

NOX seems to be a common problem with 22Rs..


I solved the NOX problem by adding a sheet metal gasket after the cat with only about 1 sqin of holes in it for the test.    I post a link or the picture when I find it...........


(86 22RE)

[BUDDERS]

I am having that issue too with my '87 22re.  Here in Cali, the max NO limit on my Federal rig is like 732 PPM.  My truck was over 1200.  I got some RXP gas kicker to run through the gas tank, retarded the timing to 2 degrees and re-routed the vacuum to the EGR valve to open as soon as the throttle opens.  All of these steps help keep the combustion chambers cooler which is supposed to lower the NO value.  I will see for sure when I go to smog it again.

[Rocksurfer]

Big tires can really screw with the #'s, my Samurai did the same thing. We just tossed it into low range and it passed.

[Plekto [OP]]

But that's the odd thing.  Back-pressure is fine and should be identical if the engine is running at the same rpms. but merely a different gear(manual transmission, not automatic). Passes all tests by a large margin except for this.  The last few years worth of tests never turned up an anomaly like this, either.  The readings were always lock-step with each other, as you would expect.  

max at 15mph - 1085.  measured: 1840 RPM 1641  (2.5x 25mph?)
max at 25mph - 1120.  measured: 717.  RPM 1752 (passes fairly well)

If anything, NOx should go *up* as RPMs and temps increase?  The only thing that I can possibly think of is the technician started it in 1st and then shifted to 2nd in the middle of the test(more like lurched badly - whole vehicle wobbled and bounced on the dyno).   Would this cause such a problem?  If anything I'd expect it to also show higher on the other parts as well, but it's almost exactly the same.

Q: if it is the EGR, is there a way to force it to be 2x more sensitive?

[emsvitil]

The 2 speeds (15 & 25) may be at the same rpm, but they're at different loads.

(forget which speed has the higher load)


With different loads, the nox will vary.


The restriction will make it more sensitive.


See:

http://board.marlincrawler.com/index.php?topic=71916.0

[yotarunner85]

If the cat is not hot enough NOX can be high at low RPMs, then warm up enough to be lower NOX at higher RPMs. Try again and make sure the cat is nice and hot. The cat is more efficient at high temps. Lowering the timing 2 or 3 degrees can help too.

[Plekto [OP]]

I like the restriction plate idea.  I suspect that even dropping it to lower timing plus 2 inches(vs 2.25) with the plate would be enough.  I never lug the engine at 1600rpm in 2nd or 3rd gear, so the issue seems to be not that I'm polluting so much as the test is at a useless rpm/mph range for my gearing/tire combo.  Evidently this is a common issue as well with Porches - no back-pressure if you're lugging it, but the thing's undriveable (literally) if you ARE doing that.  So nobody does and they don't pollute excessively in normal driving.  Except when taking the screwed up test.  Is there anything that I can do to make the EGR more sensitive/react quicker?  I'd like to solve that part of the equation with one $30 part, but the question is EGR(if they make a more sensitive one), the temp sensor(no idea on age - probably ~10 years old(age of current engine), or a new O2 sensor?(2 years old currently)  

Probably just drop a bottle of kicker in it and set the timing to 3 degrees.  I usually put some Lucas injector cleaner in the tank and I forgot this time, so it's probably burning a little lower octane than normal.   If this was any other state, I'd be fine, of course.  Yes, I ran the thing around town for 30 minutes before the test.  Proper temp there.  New air filer, oil change, and spark plugs.(normally replace plugs every smog check).   

Dang I hate this state.  Btw, did you hear about the insanity where now that there are diesels are out that pollute 30% LESS than gasoline engines, CARB wants to ban diesels based upon classifying it as a carcinogen?   

[yotarunner85]

  Q: if it is the EGR, is there a way to force it to be 2x more sensitive? yes
                                                                                                                                                                                                                                                                                                                                                                                                                                                          Have the same problem with my 85 22RE (cam, big valves, higher compression, & header) every smog. My NOX were at 1200. So what I did is tee into the vacuum line that goes to the EGR valve then tee in to the ported vacuum line off the throttle body & hide the vacuum line under the intake plenum. What this does is at part throttle the ported vacuum source applies more vacuum to the EGR valve than normal causing the EGR vavle to open more & that = less NOX. After the smog I take the vacuum line off and throw it in my glove box for next time. Been doing this for the last 8 years. Also what helps is making sure that the cat is real hot. I sit outside the smog shop & run the engine at 2000 RPMs untill he is ready to smog it. Good luck.

Copied from my post from another smog topic.

http://board.marlincrawler.com/index.php?topic=71916.0;highlight=smog

[yotarunner85]

Also have my results posted in that thread.

[Plekto [OP]]

got a pic/diagram?  Somehow my old brain isn't figuring out what to do from the description.  I'd love a $5 fix(don't think it'll make much difference in how it runs, since the EGR is on most of the time driving around anyways - just isn't apparently reacting quick enough)

[emsvitil]

What temp sensor?   (the one with vacuum lines?)  




http://www.autoshop101.com/forms/h61.pdf

tells you how the toyota EGR system works......

(and you can see why more back pressure increases the sensitivity at the modulator)

[Plekto [OP]]

I've been reading that(thanks) and I think the problem (due to other symptoms such as 1-2 shift bogs down) is that the Vacuum modulator assembly needs to be replaced as it looks like the original part.(def clean out the screen first, though.)

If this fails, it's off to the exhaust shop to unhook the cat, o2 sensor(have plate for that hole), and exhaust and run some seafoam or similar to blow out the carbon and gunk.(don't want that crud in the cat, sensor, or muffler, naturally).  Because the only thing that will fix it at that point is getting rid of the crud in the cylinders.  With 200K on the engine(runs perfectly fine as 75% of that is highway commuting) and no other symptoms, if it's not the EGR, then it's just full of gunk that I need to blow out.

Though, I hear that Toyota sells a similar product (engine pre-tune IIRC) that supposedly does the same thing for cleaning the throttle-body.  Any experience with either of these on old engines?

EDIT - I found some before and after pics.  The stuff seems to work to get out maybe 30-40% of carbon at most on a dirty engine(far from a miracle cure), but def needs to be run with the exhaust parts you want to save OFF of the thing.  Apparently using it and clogging your cat is a fairly common "oops".   The stuff itself won't cause any damage, but the junk it spews out certainly will cause all sorts of ills.

[yotarunner85]

I've been reading that(thanks) and I think the problem (due to other symptoms such as 1-2 shift bogs down) is that the Vacuum modulator assembly needs to be replaced as it looks like the original part.(def clean out the screen first, though.)

If this fails, it's off to the exhaust shop to unhook the cat, o2 sensor(have plate for that hole), and exhaust and run some seafoam or similar to blow out the carbon and gunk.(don't want that crud in the cat, sensor, or muffler, naturally).  Because the only thing that will fix it at that point is getting rid of the crud in the cylinders.  With 200K on the engine(runs perfectly fine as 75% of that is highway commuting) and no other symptoms, if it's not the EGR, then it's just full of gunk that I need to blow out.

Though, I hear that Toyota sells a similar product (engine pre-tune IIRC) that supposedly does the same thing for cleaning the throttle-body.  Any experience with either of these on old engines?

EDIT - I found some before and after pics.  The stuff seems to work to get out maybe 30-40% of carbon at most on a dirty engine(far from a miracle cure), but def needs to be run with the exhaust parts you want to save OFF of the thing.  Apparently using it and clogging your cat is a fairly common "oops".   The stuff itself won't cause any damage, but the junk it spews out certainly will cause all sorts of ills.

Before you go pullin' your truck apart lets check afews things first.
1. Have you checked to see if your EGR valve is working?(some times they get stuck & you have pull it off and clean them out)
2. Check for proper vucuum line routing and check for any damaged(cracked or blocked)vacuum lines also check the vacuum switch.
3. Use a vacuum gauge to see if you have vacuum at the EGR while driving.
4. Check the vacuum modulator operation.(see shop manual if you have one)
5. Check for any damage to the cat.

Some other things that can cause high NOX are higher than normal compression from carbon build up in the cylinders.
In that case a cylinder de-carb may help.

A high flow exhaust (header, high flow cat, larger exhaust tubing) will lower the back pressure,
which may have an effect on EGR operation. (check for enough vacuum at the EGR valve line)

Also larger tires without having the truck regeared to close to stock overall gearing will put an extra load on the motor
and increase emissions.

By the looks of those numbers it looks like the EGR wasn't working at low speed or the cat wasn't hot enough.
I know you said you drove it before the smog but how long did it sit before the test was started?
If it sat long enough the cat may have cooled down to much.
After checking that the EGR system is ok you might want to have a pre-test smog check run and make sure the cat is hot.
I sit outside the smog shop and run the engine at about 2,000 rpms untill he is ready to run the test.
I know it sounds silly but I have gone through alot to get my truck to pass due to all my not smog legal engine mods.
The state of california wants older trucks like ours to fail and get taken off the road.
I agree with trying to make our air cleaner and would love to convert my truck to cleaner burning propane,
but thats not legal in california.(go figure? sounds stupid to me). Anyway good luck with getting your truck smogged.

[Plekto [OP]]

Cat was properly hot.  Last time I tested the truck, two years ago, it wasn't and it got scores of 1000(squeeked by).  750 is a great score for this setup.

Yeah, the rest of the system is fine.  It appears as if the EGR is just too lazy/slow due to the exhaust I have on it.  It's a CA legal header and exhaust, even.  Go figure.  So I have three options:
1 - fix/replace the modulator and hope it fixes it.  Is there a trick to getting the modulator apart to clean the screen inside?  Or should I just order a new one for $35 online?
2 - do the hose trick and trick the thing into being more sensitive.
3 - put an artificial restricter plate in the exhaust.  I suspect 2.0 vs 2.25 inch would be enough in my case.

[yotarunner85]

Backing the timing down a few degrees may be enough.(up to 5 degrees, I wouldn't go any futher)

Or try the exhaust thing or vacuum line thing.

[yotarunner85]

got a pic/diagram?  Somehow my old brain isn't figuring out what to do from the description.  I'd love a $5 fix(don't think it'll make much difference in how it runs, since the EGR is on most of the time driving around anyways - just isn't apparently reacting quick enough)

You tee into the vacuum line from the P port on the throttlebody and then tee into the vacuum line that goes to the EGR valve.
Hide the vacuum line that goes between the two under the intake manifold.
What this does is add about 5 inches of vacuum to the EGR causing it to open sooner and open more.

Dont have time to take a pic or draw a diagram leaving for the weekend. If you need more help I'll draw one or do a pic next week.

[emsvitil]

The top of the modulator pops off so you can get to the filter inside.

If you want to see your backpressure, plug an old fuel pressure gauge (0-10psi) into the hose that's connected dead center at the bottom of the modulator.

Without the restrictor in the exhaust, you could hardly see an pressure at all and occasionally some vacuum (stock header, free-flow cat, turbo muffler).    With the restrictor, you'll see some backpressure.

With headers, your backpressure probably doesn't exist, and you may actually see some vacuum here as the headers suck out the exhaust.......


Goto bottom page 3 here:  http://www.autoshop101.com/forms/h61.pdf

Port R doesn't do anything at smog test speeds.    The vacuum from port E won't make it to the EGR valve without backpressure (chamber A) pushing the modulator closed...........

[Plekto [OP]]

Well, I backed off the timing to stock(runs like crap now) and dumped a whole bottle of octane boost in it.  And somehow managed to pass.  1050 or so at 15mph and 350 or so at 25mph.  Basically EGR not engaging at all, but I managed to get a bit lucky.(the fuel additive did drop 300-400 off the NO reading, so without it I'd have been out of luck.

But the other issue is of course that HCs are right at the limit.  I guess it's to be expected given that this is La-La Land and the idiots in charge here make it impossible for any engine with over 150K miles to pass.(anyplace else the numbers would be more than acceptable - the engine runs very well normally.(have to set the timing back to 10 degrees tomorrow)

Probably the last time I ever smog it, though.

[jimbo74]

Well, I backed off the timing to stock(runs like crap now) and dumped a whole bottle of octane boost in it.  And somehow managed to pass.  1050 or so at 15mph and 350 or so at 25mph.  Basically EGR not engaging at all, but I managed to get a bit lucky.(the fuel additive did drop 300-400 off the NO reading, so without it I'd have been out of luck.

But the other issue is of course that HCs are right at the limit.  I guess it's to be expected given that this is La-La Land and the idiots in charge here make it impossible for any engine with over 150K miles to pass.(anyplace else the numbers would be more than acceptable - the engine runs very well normally.(have to set the timing back to 10 degrees tomorrow)

Probably the last time I ever smog it, though.

honestly, i don't see everyone's gripe about smog. if your truck ran properly, it would pass.....

you say no engine with 150k passes, i just smogged my ranger, with no issues, and nothing done to it, drove it for maybe 5 miles from parked, to the smog place.... yeah, they dynoed it, had low numbers...... i use the crappiest gas possible, and i have 171k on it.... i haven't changed the spark plugs in 5 years, haha

[Plekto [OP]]

The issue with older engine designs like this is that the HC levels creep up over time and there's nothing that you can do about it short of a rebuild.  Other than the EGR not activating at under 2000 rpm in 1st or 2nd due to the cat-back and headers (I never drive it at less than 2500rpm if I can help it anyways), the rest of the truck passed quite easily.

Other than the fact that the HC has been creeping up over time towards the limit here(which seems to be going *down*)
Yep - check this out - from my actual tests:

Los Angeles CARB Limits 2008 1987 4Runner:
HC 131/101
CO 0.87/1.10
NO 1085/1120

Los Angeles CARB Limits 2010 1987 4Runner:
HC 131/101
CO 0.61/0.77 (29.9% less/30% less)
NO 1085/1120

So, yes, they are messing with us behind the scenes in order to get us off the roads.  In the past the limits stayed the same or went up slightly to compensate with age.  Now they are dropping them.  They expect my truck to pollute 30% LESS in two years time?  

Also, I found out that the governmnent doesn't have actual data in their computers for original limits/specs for pollution farther back than 1988.(and no 0 mile say, 1980 cars to test)  So they're basically making up numbers for vehicles from 1976-1987.  Ie - it's impossible pretty much for a 22R with carbs to pass in Los Angeles any more without a new engine/swap.  

[yotarunner85]

Glad you passed smog. Backing the timing down helps alot with NOX levels, keeps the cylinder temps down because the combustion starts later in the cycle.
Has less time to build up pressure, so you lose power, runs crappy, but pollutes less. Thats why you are allowed to retard the timing and not advance it.

Yes older engines designs aren't as clean burning as newer ones. Do they want you to pollute 30% less, no. They want us to pollute 100% less.
Is that possible? I don't know.

As far as smog data, they have alot. Everytime an old Toyota gets a smog done they see the good & bad, and if they see that a larger percent are passing
at a certain level they can lower it to just above that level. When I first started taking smog classes I was told they start high and slowly lower the max levels down.
They will eventually get to where they will level off and stay the same.

I agree with jimbo74  "if your truck ran properly, it would pass....."
My friends 84 Toyota with 250,000+ miles passes no problem, well within the limits, but it is all stock and well mantained.
My 2002 Ford Explorer with 175,000 miles passed last month with all 0's. Both the 15 & 25 mph tests. 0 HC, 0 CO, 0 NOX.
My Toyota doesnt pass because of all the mods I have done to the engine. If I put it back to stock it would most likely pass.

Yea they want older vehicle off the road because they pollute more just need to find a way to clean them up to keep our classic Toys on the road.
There is an organization that is fighting to keep classic cars on the road. Just cant think of the name right now.

[Rocksurfer]

I'm sorry I must be one of those people messing up the numbers since I just smogged the 4Runner and it flew through with flying colors with 211,000 miles on the od. Maybe we should stop keeping our trucks tuned and running properly to bring those numbers back down. 


Good to hear you finally passed too, keeping another Toyota on the road.

[Plekto [OP]]

Yeah.  So Cal smog is far stricter than even the rest of California.  Every time it's a nail-biter for anything over ten years old.

[Rocksurfer]

I wasn't worried, as long as the maintenance is taken care of I've never had an issue even my 80 used to pass 1st time through.

[Plekto [OP]]

Yeah, it was that way up to and including two years ago.  Then they dropped the CO limits by a flat 30% on all used vehicles from what I can tell.  So NEXT time it has to be smogged, it's going to be a major headache if you are in So Cal.