Failed smog: Gross Polluter in CO, passes by 50% on hydrocar

[Guest Anonymous]

I own a 76 datsun 280z, completely stock. It was transferred to me in january under a failed smog inspection. It had pretty much bombed the hydrocarbon catagory. I had it steamcleaned which made the air sensor gasket go(but i replaced) and fixed a leaky fuel pump line. Then i had it re-tested. The report went like this: Hydrocarbons: pass by 50% margin @15/25 mph. Carbon Monoxide: fail by 2x the max. (gross polluter). Someone told me this could be because it was running lean. I know a little about datsuns but i don't know of a specific problem that could cause a car to do so well in 2 categories (the other category max was like 1200 ppm and it only had 300 ppm) and miserably fail Carbon Monoxide. Could it be that the catalyzer is shot? or maybe the airflox max sensor?

[fl327]

the afm goes bad in a lot of those cars, i would check that first, and failing that bad i would replace most of the smog system except the cats, then test again, if cats fail, then replace, and watch out, i think your car has to super pass by a large margin to lose gross poluter status, and you have to go to a smog station with a tester with a higher liscence, and chevron doesnt usually have one of them cats on the premisis.

[randy 77zt]

once car is a gross pollutor in california it has to be inspected every year at a test only station.the vin on the car is branded for life in ca.you are running lean.check o-rings around injectors by squirting them with carb spray.make sure there are NO vacuem leaks or air intake boot leaks.the air flow meter has an adjustment in it but that is used only if all other parts are to new specs.i put new injectors in my 77 and it ran like a new car.remember that when 280z"s came out the gas had no injector cleaner in it.back in early 80's there were a rash of 280 exhaust manifolds cracking.it was caused by heat from a lean cylinder from clogged injectors.if car is running properly they will sometimes pass with a hollow convertor because all of the fuel is burnt in engine .convertors are a mop up for poor combustion and any mechanic that says throw a new cat on it doesnt know how totune an engine.

[Guest Anonymous]

thanks a lot for the info on leaks. I will do that and i had originally planned to scrap the a/f/m anyway. thanks again.

[Guest the_dj]

I replaced the O2 sensor on my ZX (don't know if you have one) and I dropped to 3ppm hydrocarbons and like 0.0005% CO. Not for sure about that second number, but the inspector turned to me and said "Dang, most new cars can't do this!"

 

DJSS

[DavyZ]

Randy is right in saying that the car is "branded for life" once it becomes a gross polluter--that's why it is so very important that a smog mechanic check the car FIRST if there are any doubts, otherwise you have to bow to the smog gods every year and take your $40 lumps. Stupid IMO that it must be done every year...three years in a row, cool, but for life??? They are trying to do what they can to "tax" the car into oblivion; in other words, they are hoping the owner think it too much of a pain to keep it, and they hope it goes to a junkyard or something.

 

Still, if the car is a decent runner and you get it to pass the emissions testing, it may be worth hanging on to.

 

BTW, I'm a Davis graduate GO AGGIES!!!!

 

Davy

[Guest Anonymous]

hey, so if i failed as GP i have to retest every year 4ever? That is bullshit. Another reason to buy a 240. By the way i think it is the air flow meter i will buy a new one. i need the car to last me untill next winter so ill put up with the smog crap for now. But when i get a project 240z, out comes the plasma cutter.... want 280z parts? The engine&tranny can go for real cheap, so can body. you can have whatever i dont need.

[Guest Anonymous]

K. I am going to contine posting how i'm fixing the car, so it can help people with problems that are the same as mine.

So far, I have done this: Coolant flush. Oil flush. Systematic Electronic Fuel Injection test(resistance, conductivity, voltage). Checked timing. Steamcleaned engine. Replaced fuel filter.

The above has helped enourmously, especially the fuel filter swap. It starts much faster in the mornings, and starts up instantly after the car has been turned off for a little while.

It has developed some strange driveline noises which are going to have to wait until they get louder.

Also, i wrote motorsport about the problem and they have reccomended a air flow meter replacement...

I will continue posts as i complete the fix.

[JBSRace1]

As a genaral rule if you Failed on Co it is running rich not lean. Hc is efected mostly by ignition Cap,rotor,plugs,wires. Nox is from to high combustion temps, EGR, Cat are the number 1 problems. If you where lean your Co would be low and Nox would also go up slightly becouse of the extra combustion heat from being lean. A air flow sensor can cause a rich condition but it should also make it run ruff as well. As stated above the O2 sensor will drasticly effect Co and need to be changed every couple of years and most never get changed until there is a drastic problem. Also a Vacume leak on a Fuel injected car will make a lean condition and the computer will try to correct it by making a rich condition.

If you have a good mechanic at a shop you trust they should be able to find your problem fairly easy.