Help with failed emissions

goser · #1 12-11-2007, 06:51 PM

Well, the good news is the car was cheap...

Emissions test failed (and just) on the NO test. There are no codes. The only thing I can offer at the moment is there is a fuel smell from the back of the car. Just wondering if there's any common failure with these vehicles where I might start looking.

goser · #2 12-12-2007, 06:40 PM

What should ignition advance be on these engines? I'm looking at about 20* at the moment. Is there any way to adjust?

muff34 · #3 12-13-2007, 03:20 AM

bet everone is wondering what car you are referring too.Is it your 99 sunfire? what are the details?

goser · #4 12-13-2007, 10:35 AM

Hmm...that would've been a good thing to add...thanks. Yes, it's a 1999 Sunfire GT 2.4L.

The B1S2 Oxygen sensor output voltage is pretty much flatlined, so I'm going to start with replacing that.

goser · #5 12-13-2007, 12:46 PM

K, checked the oxygen sensor output against the one on my truck and the pattern is similar, so I guess they're okay.

Where the frick is the EGR valve on these things? The Chilton's manual arrow seems to actually point to the starter... Grrr!

Don't know if this matters at all, but I pulled the intake off to clean the throttle body, and when I started her up to spray the cleaner in, there was a pop and blue smoke came out from the throttle body. I'm hoping it was just unhappy to start without the intake hose, but could this be a sign of worse things?

Finally, the MAP sensor hose was corroded, would an incorrect MAP sensor reading cause high Oxides of Nitrogen?

wrightz28 · #6 12-13-2007, 12:50 PM

Only a EGR problem will cause a unacceptable NOx reading.

edit - "normally"

goser · #7 12-13-2007, 01:17 PM

Alright, thanks. Would you be able to point me to where the EGR is? I can't for the life of me find it.

wrightz28 · #8 12-13-2007, 01:25 PM

Sorry bud, Cavy's aren't my cup of tea, but, it has to vent back into the intake mainfold along witht eh PCV valve so trace to the tubes to find wich is wich.

goser · #9 12-13-2007, 01:40 PM

So I just read that the '99's may or may not have an EGR valve, so I'm guessing I'm one of the lucky ones without. So, how would I clean the EGR system on this vehicle?

wrightz28 · #10 12-13-2007, 03:52 PM

"The linear EGR valve, used on the 1996-00 2.2L and 2.4L engines, is designed to accurately apply EGR to an engine, independent of intake manifold vacuum. The valve controls EGR flow from the exhaust to the intake manifold through an orifice with a PCM controlled pintle. During operation, the PCM controls pintle position by monitoring the pintle position feedback signal. The PCM uses information from the Engine Coolant Temperature (ECT) sensor, Throttle Position (TP) sensor and the Mass Air Flow (MAF) sensor to determine the appropriate rate of flow for a particular engine operating condition. "

Hope that clears things up a bit.

goser · #11 12-13-2007, 06:09 PM

Thanks for the reply. According to the wiki article on the Quad-4 LD9 Engine: "This engine received a minor update halfway through the 1999 model year that eliminated the EGR, increased the compression ratio from 9.5:1 to 9.7:1, and switched from low impedance fuel injectors to high impedance." No wonder I can't find the EGR valve.

Now, the good news is I got a second opinion with the emissions test and passed! However, it was very close, so since I now qualify for four more tests at half price I'd still like to figure out why my NOx readings are so high. So, any further advice would be welcome!

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