FAILED EMISSION TEST

[rover3l]

I had to get my MA inspection today as I have now registered the Q in MA. It failed the emission test. The inspection station think it might be the catalytic convertor as the failure was on CO. The grams per mile were 35 whereas the limit is 20. I have 60 days before I have to get a retest.

As posted yesterday the auto shop who are doing other work for me discovered a split vacuum hose an elbow shaped under the Plenum. The shop told me not to drive it muh as it would be dumping too much fuel into the cats. It has probably been like this for a while so I don't know if I am facing having to replace the cats $$$$$ or whether the hose replacement will effect a fix. Could their also be other causes?

[metaverse3]

Clean the EGR circuitry completely and the IACV/Throttle unit. Check the PCV valve and replace . Basic Tuneup is probably in order. The only instances of fuel dumping in the cats that I can think of is

* where the O2 sensor is faulty throwing off the fuel mixture* Where one of the ignition coil or coils is/are dead dumping unburnt fuel into the cats* Fuel injector leaking dribbling down the cylinder walls leading to flooding and unburnt fuel..

Post back and probably more folks will contribute with their experience..

[Q45tech]

Obviously IF the vacuum hose that feeds the fuel pressure regulator is bad the idle and cruise fuel pressure will rise to 44 psi vs the design of 34 psi

44/34=1.2941176 take square root = 1.1375928 or almost 14% too rich.

The ecu tries to correct by adding more air at cruise but may be unable to do so at idle because it doesn't know something is wrong because the O2 are not monitored sucessfully at idle after they cool [IFFY SOMETIMES YES SOMETIMES NO!]

Why one always checks fuel pressure at idle, at cruise, and at WOT max rpm and monitors it, to see the ramp up rise and fall as the accelerator is opened and closed.

Common fault and confusing because the added air from the vacuum leak might over come the extra fuel created by the pressure increase.......depends on the leak size in the hose and where it is along the hose.

[DAEDALUS]

If it's running rich it would show up. How was the HC reading?

[rover3l]

hydrocarbons were within spec, it was only the CO that failed

[Rex]

Do they give you the exact readings, acceptable range and can you tell us what the procedure is for testing?

[rover3l]

The MA test is described below:

Light-duty gasoline vehicles model year 1984-1995 will receive a tailpipe test, with most tested on the dynamometer, a treadmill-like device that simulates real-world driving conditions. Vehicles capable of both two-wheel and four-wheel drive are tested on a dynamometer in two-wheel mode. All-wheel drive vehicles will be given an alternative test that includes a visual check of emissions components and a two-speed idle test.

My results were

HC reading 0.44 grams per mile, limit is 1.2 PASSCO reading 35.99 g/mile, limit is 20 FAILNOX reading 0.06 g/mile, limit is 2.5 PASSCO2 reading 586.04 g/mile, limit Not Applicable FAIL

[DAEDALUS]

Why would combustion create CO and not CO2? Combustion would prefer CO2. Happens when there's not enough oxygen in the mix. Fix the vacuum leak and then retest.

Edit: Was the engine fully warmed up when you did the test?.

[IvoryJ30t]

just from the oxides of nitrogen reading, i would think that the cats are good, or the car was not fully warm.

if it was running rich, why arent the unburnt hydrocarbons higher?

[rover3l]

I didn't think about the car being fully warm. I drove the car 2.5 miles from home from a cold start straight to the testing station.

Vacuum leak will be fixed on Tuesday

[DAEDALUS]

That could do it. I imagine it's fairly cold where you're at. Cats need to be at about 900*F or higher to be really effective and don't do anything when cold.

[dareo]

When i tested my Q, i thought they cheated the results. All numbers were almost zero.