SMOG FAIL...High HydroCarbons...any help?

[Mylesofsmyles]

The victim is a 95 960...2.9L automatic.

It failed SMOG in CA today for high Hydrocarbons...

Maximum: 57ppm
Average: 31ppm
Measured: 72ppm

The SMOG inspector indicated it could be spark plugs...

Any other guesses....this is a SMOG inspection to get the car sold, so I just want it to pass.

[BryantTF242]

check the gap and make sure all is well, make sure no leaky injectors, was the O2 high? might be a vacuum leak causing lean misfires

[Mylesofsmyles]

Everything else was nominal...

Oh, and it only happened on the 15mph test, not the 25mph test.

[ziddey]

Can you post the smog sheet?

Definitely check/replace the spark plugs.

How old is the o2 sensor?

As long as your NOx is under control, it should be easy to get down to level.


The 15mph is the first test. How long/hard was the car driven before smogging? It sounds like if you got the cat a bit hotter, it may pass. Did NOx drop between 15mph and 25mph as well?

[Mylesofsmyles]

Maybe drove for 15 minutes and 12 or so miles before...

Can't scan but I can post specs....

Anything in particular you're interested in?

[BryantTF242]

post all the readings.

[Mylesofsmyles]

15mph test...

RPM 1820
% CO2 Meas 15.2
% O2 Meas 0.0

HC (PPM)
Max 57
Ave 31
Meas 72

CO (%)
Max 0.33
Ave 0.04
Meas 0.16

NO (PPM)
Max 479
Ave 87
Meas 113

RESULTS...FAIL


25mph test...

RPM 1771
% CO2 Meas 15.2
% O2 Meas 0.0

HC (PPM)
Max 33
Ave 18
Meas 33

CO (%)
Max 0.31
Ave 0.04
Meas 0.13

NO (PPM)
Max 487
Ave 71
Meas 18

RESULTS.. PASS

[745 TurboGreasel]

insufficient warmup

[Mylesofsmyles]

Originally Posted by 745 TurboGreasel

insufficient warmup

Really??

You think that's it???

[BryantTF242]

yeah your running rich, little to no oxygen in talipipe, so no misfires, CO(not as much as HC bviously) and HC high so excessive fuel being incompletely and partially burned.

[Mylesofsmyles]

Rich, because it's still warming up?

[745 TurboGreasel]

The cat has to be HOT to work right, and that takes longer to achieve as it gets older.
Smogger is required to do 3 min of no load high rev or so, but that may easily not build enough heat in the system, adn they can then sell you a brand new cat install or whatever, knowing all they have to do is run the car for 10 min instead of 3, and it will pass regardless. I see it a lot.
Basically, go drive circles while you wait, and be damn sure they don't let the car cool down for a half hour.

[BryantTF242]

possibly, when my car warms up it runs so rich it pops and crackles out the tailpipe on decel, but after its warm it runs perfect. the best possible test will be at operating temp so get to the smog place with noone there so the car stays nice and hot, hot catalytic converter = more HC and CO being mixed with O2 to make lots of CO2 and H2O. the cat is like a furnace for unused fuel, it burns it all up if the engine cant and uses the oxygen to fuel it, all things that come out of the exhaust ports every revolution.

good luck bud i hate smog stuff, tricky to figure out whats doing it. hope you can figure it out!

[Mylesofsmyles]

So, strong enough chance I'll pass if I get the cat hotter??

I'd like to avoid as much under hood work as possible.

[945ti]

Hc is unburied fuel or really really rich in some cases. Spark miss, dirty oil, very rich or messed up fuel tank vent are common..

Cruddy coil pack or wiring to it is ever common on 960s, running rich with gassy oil, rotted vac hoses on the volvos common, fuel fill hoses and caps can set the thing off on 7/9 cars, as can an egged out filler neck. You are pretty close. Tighten up and check everything. Maybe run it on some *caugh* alcohol...runs a little rough but oh so fresh and so clean clean.

You are pretty close...I'd guess a minor miss or little fuel vapor escaping or in the oil or some such and it would pass. Sometimes just an oil change and running it a little longer does it. Not much oxygen so unlikely miss...fuel tank vent or maybe oil change or a little cool. Maybe crack the gas cap before hand? Do they vacuum test the fuel tank in kalifornia?

[Mylesofsmyles]

Thanks James:

Yeah, the oil is pretty fresh...

There seems to be no misfire that I can feel.

Evap and all that was good, so I don't think it's fuel vapor escaping.

[falunbrick]

on a friends 76 hilux it failed for high hc's at idle, we left the smog shop, next day we warmed up the car and beat the crap out of it till the cat was glowing, brought it in and bingo bango passed on the first try. You may also try splashing a little e85 in the tank if its available near you.

[Cheezmo]

Originally Posted by falunbrick

You may also try splashing a little e85 in the tank if its available near you.

Why not just a bottle or two of octane boost?

[RESURRECTED]

Originally Posted by 745 TurboGreasel

insufficient warmup

this. you have high HC's, but appears almost no O2. just recheck plug gap, and get it nice and hot before going in.

[volvorod85]

Double check the spark plugs and keep it hot....bet it will go through as is if it was hotter

Mark

[MasterBlaster]

Whatever you do, don't drill a tiny hole (1/16"-1/8" or so) in the pipe just before the cat, allowing a bit of extra air to be sucked in during the driving test. Despite supplying more oxygen to help burn any excess fuel, and ignoring the many difficult cars our shop got to pass smog this way, don't do it, as it would be cheating, and you wouldn't want to to that!

[745 TurboGreasel]

Don't, you fail the test if the computer suspects sample dilution.
If you need to heat the cat, and can't get enough by driving, cripple one plug wire, and rev till you have heat. burning one cyl's worth of gas will heat a cat up pretty quick.
OBDII would narc you off for that kind of shens.

[MasterBlaster]

Originally Posted by 745 TurboGreasel

Don't, you fail the test if the computer suspects sample dilution.

That's why you're drilling before the cat, and not just dumping a ton in later, simulating a rusted-out muffler, which would screw up the smog computer's expected tailpipe mixtures. The tiny hole just helps the chemical reaction in the cat... no different than other cars with pumps that inject air into the exhaust manifold on the way to the cat (Volvo 850, for example). We're "injecting" a whole lot less, just enough to nudge the numbers down a bit.

[thelostartof]

Last time I took cars for smog with small exhaust leaks before the cat they all failed. Fixed pre cat leaks and the cars passed with zero issues.

That is just my experience . . . Some leaks were as small as pin hole leaks in welds on the header.

[Lando]

Originally Posted by MasterBlaster

That's why you're drilling before the cat, and not just dumping a ton in later, simulating a rusted-out muffler, which would screw up the smog computer's expected tailpipe mixtures. The tiny hole just helps the chemical reaction in the cat... no different than other cars with pumps that inject air into the exhaust manifold on the way to the cat (Volvo 850, for example). We're "injecting" a whole lot less, just enough to nudge the numbers down a bit.

Those air injection systems either use a pump or solenoid valves to make sure that no air is getting out.