So let's make this simple. My 1980 GS can't pass emissions. I bought after it had sat in a field for 16 years hoping to get it back on the road. I've got the car running good, doesn't smoke except a little at start up, but it's way off the charts on HC and CO. To be exact; passing here in Oregon is HC lower than 220, and CO less than 1, I'm reading 2300 and 9 respectively. I've gone through as much of the emissions systems as I know how and I only got the HC down from 2600. I've rebuilt the carb, new plugs, distributor cap, wires, coils, etc... but it's not even close to passing. Any tips of something I may have forgotten or done wrong? I'm not very familiar on the Nikki carbs, does turning the mixture screw clockwise richen or lean the A/F mixture. Any help would be awesome (only 8 days left on the trip permit). BTW it's not dynamometer testing, just idle.

Thanks in advance,
Ben

 

Whats the exhuast on it? Still the thermal reactor? Is the air pump working correctly?

 

It's the original exhaust, thermal reactor included and the air pump moves air but at the moment I have no way to test it's pressure. I haven't confirmed if the secondary air control valve is working or not yet. Other than that, all the emissions solenoids are working and I've adjusted the idle sensor within spec.

 

DEQ as in disqualified? Also Oregon has testing on an 80? well then. Get the car registered in washington?

 

DEQ is the department of environmental quality (basically just smog testing). The cut off year for emissions is 75 but there's been some debate of whether or not it might get pushed further up. As for Washington... Not sure about that, some of my friends have suggested registering it in a different part of Oregon where DEQ is not required, but I'd rather not get into that and instead try to get the car running like it's supposed to.

 

The exhaust system has to be in perfect working order. The thermal reactor and heat exchanger have to be in tip top shape. The thermal reactors are known to fail. You may want to try and lean the mixture out a bit before taking the test. Do you have any exhaust leaks? Is the air control valve still in place?

 

Benjamin, I commend you on the "get it right" . I have an 80 that I am working on, and while I do not need to do smog testing as my car is past the testing years and my county doesn't do it anyways, I would like to be able to pass the sniffer test also. Legislations change and it would not surprise me if WA did start testing in the future. Good luck.

 

As far as I can tell there are no exhaust leaks and unless Nikki carbs are far different, it's already as lean as it can get. I did the tuning procedure detailed by Sterling located here: https://www.rx7club.com/1st-generati...e-carb-310927/
Unfortunately the one in the haynes manual requires a gas analyzer. Timing is dead on and I still have no clue how emissions can be so terribly high. Just to clarify, on the Nikki carbs there are 3 main idle adjustments:. Idle speed (large grey strait head screw on the drivers side), Idle mixture (small blackish Philips screw just below the idle speed), and the throttle stop adjustment that is a pain to get to and adjusts where the primary butterflys sit at idle. Please correct me if I'm wrong and thanks for the help so far.

 

You shouldn't mess with the throttle stop screw. Having a 5 gas analyzer in hand while tuning the carb would make matters much easier. But who has one of those laying around? The idle speed and mixture coincide in a way. I tune them both together and set my base idle at 800 rpm. You don't have to run the mixture super lean. The air pump, air control valve, and thermal reactor will take care of the rest. Are your air pump and air control valve in working order? Have you checked to make sure the air control valve isn't frozen with corrosion?

 

Today I'll go through everything with a fine tooth comb. I'll check to make sure the air control valve isn't stuck and try retuning the carb afterwards. A couple days ago I figured out the richer/power solenoid was stuck in the rich position. I've since disconnected it's power lead so that it can't get stuck anymore, hopefully that will help. The reason I'm asking about the throttle stop screw is because when I rebuilt the carb I found it way open (which explained why it idled uncorrectably high). I turned it down but I could find any specs to say where it should sit. Something else I've noticed is that air is always coming out the air vent tube near the exhaust, perhaps that's a sign that the air control valve is stuck? Thanks again for the pointers.

 

I finally removed the the air control valve and it seems to be fine, although air still comes out the cooling vent tube at idle. I'm guessing that something is not right since that would mean that the TR is being cooled instead of having fresh air put in it. With any luck a friend of mine might be able to borrow a gas anylizer from a local shop. I'll keep this thread updated best I can.

 

wishing you luck...

 

So I've come to a point where I've a few questions:
1. What controls where air from the air pump goes? I thought I was controlled by the solenoid at the front right of the carb but apparently that's the AAV solenoid.
2. Should unplugging the vacuum line that goes from the air control valve to the AAV solenoid kill the engine? By kill I mean instantly, no hunting, just dead. Before when I unplugged it the car would rev to the sky. Is this an indicator of an improper A/F mixture or TAS adjustment?
3. Is air supposed to be coming out of the cooling vent tube located at the rear of the car at idle? If not, what could cause that? Could it be a clogged TR and could that be cleaned?

Hoping to know if thing is gonna be able to pass smog soon, cause if not I don't have enough money lying around for a car that can't drive. As always, thanks so far.

 

So here's the latest. I was going through the Haynes manual testing stuff and only one thing seems to be not working correctly. According to the manual, when the engine is around 1300rpm, air is supposed to come out of the tube going from the air cleaner to the ACV. Rather than putting air out, it starts sucking it in.... Any ideas? The cooling vent pipe is still bugging me too.

 

A couple new discoveries:
1. Just confirmed the car is equipped with a California wiring harness and ECU, and yet there are no California specific parts installed on the car so... The cali only connectors are just hanging free and there is no evidence that this engine is cali spec.
2. All fuses are good including the ECU fuse. Current is passing across all terminals.
3. I forgot to mention that the 1300 rpm ACV thing (in previous post) used to work properly. I did the test two plus months ago and air came out like it's supposed to. Aka something changed since then (no clue what it was though besides tuning).

So the cali ECU has a lot more plugs that the normal one. Since none of this stuff is actually hooked up, is the ecu just running everything like normal except that the cali stuff isn't affecting anything? Could this be causing a problem of any sorts or was this just something from Mazda to save making multiple parts? I know there is a non-cali ECU so perhaps the previous owner did a swap....? Wow this is confusing. I've also since tested the ignition coil resistance and they're within spec.

The consensus it that it's not ignition for sure. I checked for the ACV leaking air. It seems fine so I guess the air is going where it's supposed to since the air pump is most definitely moving air. At this point I can really only blame tuning, the 38 year old thermal reactor, or whatever is causing the 1300 rpm issue.

Any help is greatly appreciated

 

No clue if anyone is still reading this but here's my idea...
I've got an exhaust system from my parts car (an '82 to be exact). It doesn't have the TR and all that problematic stuff and instead has a high flow cat. I'm thinking of putting the other system in, putting a block off plate over the ACV, and running a line from the air pump to the line that goes to the cat. It should just bolt right up and it would take out the tuning bit where the TR has to have enough fuel to complete combustion (aka not too rich but not too lean). In other words, leaning it out would actually reduce emissions instead of potentially making them worse (plus the TR didn't work amazing anyways). I'm thinking this should work just fine, but if not, please let me know quickly because I'm gonna be doing this tomorrow.

Other things:
Today I fixed the misfiring issue. It ended up that the connector on one of the plug wires at the coils had slid up into the boot and wasn't making good connection to the contacts.