Shark_Week

just got my GTS smogged and it looks to have barely passed. the NOX was high, but barely in there. from what i see it looks like the O2 sensor(hopefully not the cats) is not functioning very well causing it to run lean?
any thoughts or experience?

%CO2 %O2 HC (PPM) CO (%)
test RPM meas meas max ave meas max ave meas
15 mph 1420 13.1 2.7 81 21 18 0.47 0.06 0.01
25 mph 1686 13.0 2.7 47 13 15 0.44 0.05 0.01

NO (PPM)
MAX AVE MEAS
685 150 678
696 136 377

Shark_Week

sorry, not the way i typed it in there. came out weird. hope its still easy to figure out

Glenn Evans

Your NOX is high and your CO is low. This suggests that the engine is running lean. Perhaps your MAF is failing.

Shark_Week

failing maf. not good

GregBBRD

The O2 sensor should be controlling the mixture when these tests are run. While it is certainly possible that the sensor is failing, it is not uncommon to see mixtures this lean even with new O2 sensor. It is also possible that the MAF is wacky and the O2 sensor is correcting as much as it can, in order to make the car run richer. I'd put a volt meter on the O2 sensor and watch the values. A normal output (hooked up to the brain) will fluctuate fairly quickly between .2 and .8 volts. If it seems to be stuck in one position, install another MAF and recheck. If it still doesn't respond, install another O2 sensor and see what happens.

There are a multitude of things that can cause this to happen. Dirty injectors, bad fuel pressure regulator/dampers, air leaks, wrong spark plugs, bad sensors, etc., and of course, the cat could be bad...although very rare.

The GTS models also build up carbon at an alarming rate...which significantly will increase the compression ratio. Throw in a bit of oil going past the rings mixing with fuel and the effective octane drops. These two will drive up the NOX.

How many miles on this car? Does it ping?

Shark_Week

greg
total miles on car are 91,420. i have put roughly 400 miles since rebuilding after timing belt failure. the pistons have the oil holes completely drilled thru and there is no pinging. i opted not to install the new O2 sensor before i went to smog thinking it could be taken out by all the oils/lubricants and any fod that could get stuck to the O2 sensor. maybe it is time to install the new one

mickster

Was the car cold when tested or had you warmed up the cats considerably? That certainly will affect the cats performance as well.

But Greg & Glenn know far more than I do about the rest of the readings.

Michael

Shark_Week

i'm thinking they were warmed up. drove aprox. 25 miles varying the speed between 65 and 100. left it running till the test which was maybe 5 min.

Shark_Week

checked for vacuum leaks and could not find any. the injectors are fresh from the cleaners so i'm hopeful they are good. pulled the spark plugs and none looked fouled. their look confirms the lean running. need to order a fuel pressure gauge. i believe the pressure should be 48 psi at idle? also was curious to check the o2 sensor in the car, i'm guessing i would have to backprobe the wires? this correct? all other sensors are new.

Shark_Week

when cleaning the maf, what is everyone using? just carb cleaner?

Tom in Austin

There is actually a MAF cleaner, maybe carb cleaner, don't know. If you have the time, consider just sending your MAF up to Kevin at Injection Labs in CO. My car runs way better after he tested and recalibrated and it only cost $175. Oh, and with my gas mileage up by 1 MPG, I'll make back that investment easily ...

Rob Edwards

CRC MAF cleaner, comes in a gray can. Available at some of the local car part places.

http://www.amazon.com/CRC-05110-Mass...9820737&sr=8-1

Shark_Week

thanks tom for the lead on kevin at injection labs. will try some cleaning, just cuz