85 4 wd CA smog problem

[MM2car]

We moved to Ca (Davis) recently and are trying to register our 85 Tercel 4WD wagon (3 AC) automatic. Flunked the first test- needed a new EGR. Now it's borderline for NOx (~1000 ppm) so there is something else wrong. Our regular mechanic doesn't do Smog (who can blame him??) so I have another guy working on it but he seems a bit lost. Any gifted Smog techs in the Davis area? Anyone with experience on this? I can post more details tomorrow when I talk to the mechanic. Thanks- Brian

[4wdchico]

I went thru the CA smog license program in '02. Let my license lapse in '06 as I only wanted the info for self education, I don't work on vehicles for others anymore.

I should tell you that only the owner of the car or a licensed smog tech working at an official test and repair station can legally work on a car that has failed an official smog test here in CA. The better test and repair smog shops are usually Gold Shield stations. In this situation, paying someone who has not had the full formal smog training and holds a current license and does this full time at a test and repair smog station is often a giant waste of money and time.

Do you ever work on your car yourself? Are you willing to tackle some of this yourself?

Are you certain that the EGR system is really fully functional now? Lots more than just the valve going on in the EGR system. Did you get the car smog tested again after the EGR valve was changed? If so, did it pass all the other parameters in the test besides NOx?

[teranfirbt]

Back off the base timing to stock if it's not... If it is, put it at 3°... It'll run like shit, but advanced timing is another cause of nOX.

[takza]

a quote or two:

I do emissions testing where I work. If it failed on HC and CO, an oxygen sensor is a very good place to start. If CO is very high it will make NOX go down, because CO eats NOX. I wouldn't reccomend paying someone off, if your car failed emissions then there is something wrong with it, and if you fix it you're doing yourself a favor. Besides, an Ox sensor is like $40, much cheaper than paying someone off. Now if you replace the sensor and some plugs and it fails yet again, but on NOX, check your EGR system and charcoal cannister, and if they are functioning then you may need the catylitic converter. Make sure the EGR is opening when you rev the engine. Just stick your finger on the diaphram and see if it moves. I hope this helps, and have a nice day...lol


I am a emissions inspector....so this is what you need to do....
Nox is caused by tempatures in the cylndars being to high....this can be caused by several thing....higher combustion due to carbon build up on the pistons. Failer of the EGR valve to work correctly. hot spark plugs( platinum) ....so here is your cheap back yard fix....go buy 4 cans of 2+2 gum cutter (carb. cleaner).. open up the air box and start the engine....stick a peice of cardboard in the throttal stop and hold the engine at about 2000 rpm. spray the carb cleaner into the intake ...the engine will bogg down, pray ON and OFF not letting the engine stall....use all cans untill empty...this will break up the shit on the pistons and blow it out the tail pipe...more then likely youll have lots of white smoke commin out the exhaust...If you want to do it the right way...go to a repair shop and ask them for a RUN-RIGHT searvice....its a simliar prosses that does a little better of a job but it will cost around $100. it uses a system that slowly drips a special chemical into the intake...anyway...do that....change your spark plugs to a normal plug if needed...now...check that the egr works....start the car, stick your fingers under the egr valve and push up on the diaphram...the engine should bogg down and stall or come very close to stalling...if this happens then your EGR passages are clear...now vacuum check the diaphram and make sure it hold vacuum...the last thing to do is Set your ignition timming.. retard it a good amount. this will help. if you do this....the car will pass. good luck

..........

Sounds like the EGR..canister or carbon buildup? I wouldn't dump anything in it unless it has a bit of top lube in it....

[splatterdog]

EGR passages do like to clog on these big time. On my 84, the egr port thru the intake had volvanic like crust that required a drill to repoen the hole.

[MM2car]

Hey thanks- good to hear from so many people so fast. The first failure (official test) all parameters (HC, CO) were very low except NOx (high ~1500ppm vs 1000 pass) which I think says EGR. There is now a new EGR on it. Something else was replaced too- I can't remember (not O sensor) but I will find out today. The last car I worked on was a 71 Datsun PL521 so I don't know anything about Smog. I haven't seen the numbers yet but the tech said the offline shop test after working on it showed HC and CO coming up (good) but NOx running around 1000. He said it might pass (or not) but I want it fixed (yes there is something wrong) and it should run more like 4-500 ppm NOx. It seems like a vacuum leak would keep the EGR from working perfectly...??
I am disinclined to do my own work- I have too much to do with my regular job. As I mentioned, I did a lot of work on the Datsun, but that is not very helpful experience here. I will discuss all the above advice with my mechanic(s).
I can put up a much more informative post tonight. Thanks again- Brian

[MM2car]

Talked to the tech today- he dug into it a bit more and found the vacuum advance diaphragm was shot. He plugged a vacuum line (?) and got the NOx down to about 700 (1000 ppm passes). Ordering a new vacuum advance (I really don't know anything about this stuff).
Average NOx for my class of cars (according to State of CA) is about 4-500 ppm.

I think he is used to dealing with impoverished students who can't see spending money. I told him:
a) I like this car and
b) fixing it is cheaper than buying another car (at least a later model).

He thinks the O2 sensor is a bit slow but wants to see what happens when he deals with the vacuum advance. Progress. Thanks again- Brian

[4wdchico]

If you can get him to order Standard Motor Products P/N vc360 it is is the same Nippon Denso vac advance as you will get from Toyota at less than half the cost.

If you do decide to go for a new O2 sensor, I'd strongly suggest getting the NGK unit and not a Bosch. The NGK sensor tip sticks out into the ex gas stream better because it's a bit longer. So the NGK sensor stays hotter and cleaner allowing it to perform better and last longer. The Bosch is pretty much just a generic design with a 'yota connector on it and it does not take into account the extra thickness of the ex manifold where the sensor mounts.

ND also makes O2 sensors and sells them OEM to 'yota just like NGK. So my guess is that they have the longer tip as well. But I have never had one in my hands so I cannot say for sure.

[MM2car]

Thanks, 4wdchico-
A bit late on the vac diaphragm but I will keep in mind the advice about o2 sensor. Updates will appear as appropriate.

Mostly I am glad not to be trying to figure out what to do with a non-compliant car. We aren't so much into old cars, we just don't like the new ones much. When we get it legal etc, there a few other less urgent issues that we can ask about (leaks, rust etc).

It's great to find a Tercel forum. I gave my PL521 Datsun pickup away to someone on the Ratsun forum and I check it every day now to watch the rebirth of my old truck.

[MM2car]

Picked up the car from the garage Thursday. Garage replaced EGR, vacuum advance diaphragm and TVS (?). Reworked the distributor. The NOx as they measured it was ok- a little close to the margin on 15 mph but decided to go for it.
Passed this morning. NOx was a LOT lower than the garage measured it, but HC was just barely under (159/162). This is new. I am legal but I wonder if my catalytic converter is dying? Thanks for all the advice.

[MM2car]

Got the plates yesterday. Actually the DMV people were pretty nice, but that seems to be the general case here in Davis.
Kind of blew my mind when the lady behind the counter plopped two screwdrivers and a pair of pliers on the counter and said "I need your out of state plates." In Washington they mail them.
I think the high HC and low NOx were because it wasn't hot. I drove it a bit before going in and it was plenty hot but there was a line (and CA Smog takes a long time), so I left the key with the tech. First time (two weeks ago when I flunked) I did the same thing and he said he would warm it up, which he did. I guess this time he didn't. Live and learn. Thanks to you all and we will be back.

[4wdchico]

My guess on the high HC is a lazy O2 sensor like the tech suspected. You may have just gotten lucky and it passed the inspection w/o having to go that far.

The one wire, non-heated O2 sensors in older cars like ours don't stay accurate nearly as long as the heated units which are standard now. If your car gets good fuel economy, say 29 mpg highway or better, I would not worry about the O2 sensor. But if the mileage is lower than that, and you plan on putting a fair number of miles on the car, I'd suggest that you consider a new O2 sensor as it can really bump a car's fuel economy back up.

[Petros]

You might also advance your ignition timing up to 10 to 12 deg. now that you passes. That will improve economy and power, but it will blow the NOx test, so you have to set it back before your next test. The advanced timing lowers the exhaust temps, and will make your exhaust valves last longer. The 5 deg factory setting can actually cause sever heat damage to the exhaust valves, I have even seen a fully stock engine get trashed when an exhaust valve failed and embedded itself in the piston top. More of the fuel burns before the exhaust valve opens, so the exhaust gases are cooler. But it also make more heat and pressure during the power stroke, which is why it improves power and economy, but raises the NOx output.

[gatemaster]

I just passed today with my weber, federal (NM) not ca. high speed HC limit 220 I got 40, low speed HC limit I got 83. high speed CO limit 1.20 I got 0.00, Low speed CO limit 1.20 I got 0.00

[MM2car]

My guess on the high HC is a lazy O2 sensor like the tech suspected. You may have just gotten lucky and it passed the inspection w/o having to go that far.
The one wire, non-heated O2 sensors in older cars like ours don't stay accurate nearly as long as the heated units which are standard now. If your car gets good fuel economy, say 29 mpg highway or better, I would not worry about the O2 sensor. But if the mileage is lower than that, and you plan on putting a fair number of miles on the car, I'd suggest that you consider a new O2 sensor as it can really bump a car's fuel economy back up.

Probably right that the O2 sensor is marginal, and I wouldn't mind getting a bit more performance. Nevertheless the HC values on all previous tests, flunk and in the shop, were low (35-45).
I got 28-30 mpg last time I checked but that was before all the work. We do plan on keeping it forever.

You might also advance your ignition timing up to 10 to 12 deg. now that you passes. That will improve economy and power, but it will blow the NOx test, so you have to set it back before your next test. The advanced timing lowers the exhaust temps, and will make your exhaust valves last longer. The 5 deg factory setting can actually cause sever heat damage to the exhaust valves, I have even seen a fully stock engine get trashed when an exhaust valve failed and embedded itself in the piston top. More of the fuel burns before the exhaust valve opens, so the exhaust gases are cooler. But it also make more heat and pressure during the power stroke, which is why it improves power and economy, but raises the NOx output.

My regular mechanic guy definitely said setting the timing back would hurt power and economy. Anyway it looks like I need to do some more work. It is pretty sluggish at the moment. One day at a time...