supercharger emission testing

[Medman]

I just returned from an emission testing center very disappointed after my VX failed the emissions testing miserably. The following diagnostic trouble codes were given:

-Low voltage O2 sensor (Bank 1 and Bank 2)
-Fuel and Air Metering Code: System too Lean (Bank 1 and Bank 2)

The mechanic says that supercharged vehicles with aftermarket exhaust systems usually don't pass emissions testing, especially if the O2 sensors and the Mass Airflow Sensors are removed. I did not install my SC personally, but is it customary to remove these things? I really don't want to have to
RE-modify my VX back to stock, just so I can pass the $20 emisisons test.

Any suggestions?

[Cyrk]

Weird I just had my testing done with not one issue... I am also Supercharged. I doubt that a place that did the install would remove the O2 sensor or the Mass.

[mbeach]

How custom is your exhaust system? There should be O2 sensors fore and aft of each catalytic convertor, are they there?

The MAF should not have been messed with during your SC install, but the system lean code (can be a side effect of a bad/missing O2 sensor) is what really makes me worry. Lean running engines have one foot in the grave.

[Raque Thomas]

I would think that a missing O2 sensor and/or a missing MAF sensor would have your check engine lit up - no, I know that those things missing would throw a code, unless the wiring has been chaged (ie, you can add resistance and fool the system into thinking the MAF is present and working). I'm with Cyrk - I doubt the installer would have removed these items; to do so would open them up to pretty large fines. Did you try another testing location?

[nater]

Intake Gaskets! Intake Gaskets! Intake Gaskets!

They are likely leaking, letting air in that is unmetered. The O2 sensor code is probably a side affect.

It could also be the fuel pressure regulator isn't high enough, but this engine is notorious for Intake Gaskets leaking. If you reused the old ones for the S/C install, there is your likely culprit.

Nate

[Hotsauce]

I did the installation.

I agree, intake or more likely EGR leak.

John C.

[Triathlete]

When my non-SC'd VX was reading lean in bank 1 I had a clogged fuel rail. Tapped on it to loosen it up and ran some injector cleaner through the system and it has been fine ever since.

[Medman]

Thanks for getting back to me. Tell me more about these intake gaskets. Now that I think about it, about three months ago I needed to have a gasket replaced by my local Isuzu dealer. What happened was that my truck would putter and nearly stall unless I nearly pushed the gas pedal to the floor, and the surge of gas would get the truck moving again. If I came to a stop, the car would stall. I had it towed to a dealer, they replaced some sort of gasket . . . . problem solved. Lately, the same symptoms have been happening. The engine would putter and nearly stall unless I give it a fair amount of gas, then the truck would start moving normally. The dealer said something about the fuel line being clogged and the gasket having something to do with it, and by flooring the pedal I was forcing gas to clear any obstruction and the truck would go.

Do you think this could have anything to do with this "EGR gasket"? Could a blown EGR gasket cause all these emission error codes? If I get the gasket replaced like last time, do you think the truck would pass emissions? Tell me what you all think. Thanks in advance for any suggestions.

[SGT.BATGUANO]

Did you bring it in with the check engine light lit? Is this an active or a stored code. I'm pretty sure all your sensors are in place, but may not be working properly. You may have an intake or egr leak . Search those topics for more info

[Corey872]

What were your numbers on the emissions test? If your O2 sensors and MAF are really gone (or non functional) the computer is probably in open loop mode (not getting any feedback from the sensors) and dumping in a little extra fuel as a failsafe. In this instance, your HC and possibly CO would probably be high, NOX would probably be low.

If you have an intake gasket issue, this would allow unmetered air into the engine and result in a lean condition. NOX would probably be high with low HC and CO. Likewise with the ERG, if it is failed or plugged it will show up as high NOX, too.

HTH - Post the actual #'s and limits if you can.

Good Luck
Corey

[Hotsauce]

The new inspection(at least for AWD) is not with the tail snifter, they just plug into the OBD2 port and look for codes. Any code and you fail, no matter what tailpipe is doing.

John C.

[Tone]

They have passed in CA with aftermarket exhausts many times and for intial certification. Might want to clear codes before taking it in...or fix the problem - it is not the supercharger or the exhaust. Intial CARB testing and certification was done with stock airbox in place.

[Hotsauce]

That particular series of codes usually sets only during high vacuum decelleration, you probably can clear the code just before testing and test clear. Then you will be able to solve the reason without being under the gun.

You can borrow my scantool.

John C.

[nater]

Personally, I would start with new intake gaskets, check to make sure the fuel pressure regulator modification was done properly, and try again. (Yes, the S/C has to come off again for this). This seems to be the more likely culprit than sensors, injectors, etc.

Anyone else have better insight? (Agree/ Disagree?)

Nate

[MachineVX]

What you're experiencing sounds similiar to the problems I had before I replaced my intake gaskets.