Failed Emissions

[MoreIBNR]

I just failed NJ Emissions testing. HC = 158, CO% = 4.21.

I ran the diagnostics and got codes 33 (Vehicle Speed Sensor 2), 37 LH O2 Sensor, and 51 (Neutral Switch).

I don't think the latter would affect emissions.

My question is: Should I take the car to an expert, or what are my chances that I will fix the problem by just replacing the Vehicle Speed Sensor ($142) and the O2 sensors ($91 each)? I would hate to take th ecar in, have the mechanic replace these (charging full retail price which would be +$100) and hit me with a labor charge of $100-200.

I should mention that I have 160.000 miles on the car and it is a 1992. Gas mileage has been pretty poor lately also.

Thanks.

Without a doubt replace the O2 sensor. A faulty O2 will throw off your emissions and mileage. A good throttle body cleaning wouldn't hurt either.




Dave

[n00b on demand]

New O2 sensors will improve emissions and will do wonders for your gas mileage as well. I need to do the same to my car but havent gotten that trust check engine light yet

[gsodonis]

By all means, replace the sensors. When an O2 sensor fails, the ECU will default to a rich condition. Rich = unburned gas = unburned Hydrocarbons = high %HC on an emissions test.

ECU's default to rich because lean conditions can cause engine failure. Rich conditions, although rough on gas mileage, normally don't damage an engine. Overly rich can cause the washing of lubricant from cylinder walls eventually leading to premature ring and cylinder wear and failure from loss of compression, but that's outside of the normal failsafe programmed into a stock ECU. You'll see that more often on improperly tuned forced induction engines, not NA engines. Forgive the topic digression.

You can get brand new Walker direct fit O2 sensors for around $65 each from www.oxygensensors.com
Bosch and Densos are more expensive, but IMHO, functionally, they're all the same.
I replaced mine (along with some exhaust work) and my mileage increased from 21 MPG combined 80% hwy/20% city to around 24 MPG. I have a 5 speed with 4.11 gearing too. In pure highway driving averaging 80 MPH, I get a solid 27 MPG.

Replace your O2 sensors (and any other failed sensor) and retry the emissions test. You'll more than likely pass (unless your catalytic converter is shot, but that's another topic) and your mileage will increase as a result.

[wawazat??]

Give it a good run before the test too Gary. Getting cars up to full operating temperature ensures that the cat is fully lit and functional.

Todd

[MoreIBNR]

Thanks. I did run the car about 6 or 7 miles at up to 60 MPH before having it tested. Engine was at operating temperature. I don't think it was cold cats that caused it as my gas mileage has dropped a good bit in the last several thousand miles.

Originally posted by wawazat??
Give it a good run before the test too Gary. Getting cars up to full operating temperature ensures that the cat is fully lit and functional.

Todd

[sperry]

You know... my mileage has been pretty sketchy. My car's new to me, but the previous owner probably put all 190k miles on the original sensors... perhaps it's time to replace those little buggers!

There are 2 sensors total in the exhaust, right, one off each header?

[gsodonis]

The 92 - 95 OBDI SVX'i have only two O2 sensors, one on each exhaust pipe just past each header collector, just before the pre-cats.
The 96 - 97 OBDII SVX'i have a third sensor atop the main cat.

[sperry]

Originally posted by gsodonis
The 92 - 95 OBDI SVX'i have only two O2 sensors, one on each exhaust pipe just past each header collector, just before the pre-cats.
The 96 - 97 OBDII SVX'i have a third sensor atop the main cat.

Ah yes... OBD-II means the ECU has to be able to monitor catalytic efficiency... but I've got a '94 so just the 2 pre-cat for me!

I just ordered up a pair from www.oxygensensors.com... free shipping, no tax, and since I'm just a state over from CA, I'll probably have them Thursday... in time to help the fuel mileage situation before I have to drive to L.A. for the JGTC race.

[Ron Mummert]

For what it's worth, Gary, I recently posted my emission test ordeal with my other SVX, the Nissan 240S*X on another thread.
Shortened version - I failed 4 times, gradually replacing all the usual suspects a piece at a time (O2 sensor included). The final solution was a new CAT. Viola!! Car breathes cleaner than Ralph Nader's gas mask. Good luck.

Ron.

[MoreIBNR]

Sorry to hear about all that you had to replace - must have cost a small fortune. I sure hope I don't have to replace more than the O2s and the speed sensor #2. My wife is already questioning whether it is worth it.

Originally posted by Ron Mummert
For what it's worth, Gary, I recently posted my emission test ordeal with my other SVX, the Nissan 240S*X on another thread.
Shortened version - I failed 4 times, gradually replacing all the usual suspects a piece at a time (O2 sensor included). The final solution was a new CAT. Viola!! Car breathes cleaner than Ralph Nader's gas mask. Good luck.

Ron.

[Ron Mummert]

[QUOTE]Originally posted by MoreIBNR
[B]Sorry to hear about all that you had to replace - must have cost a small fortune. I sure hope I don't have to replace more than the O2s and the speed sensor #2. My wife is already questioning whether it is worth it.


1. A wife can be replaced.
2. No - I didn't spend all that much, up until the CAT which was about $240.00 installed.

Does Joisey have a limit on what you gotta' spend to cure your ills? Merryland lets you off the hook for a two year pardon if you spend at least $450.00, which I did. So I could have failed for the fifth time & still be allowed to spew forth fumes in the interim.

Ron ( Thanks for the three CATS, Subaru!).

[sperry]

[QUOTE]Originally posted by Ron Mummert
[B]

Originally posted by MoreIBNR
Sorry to hear about all that you had to replace - must have cost a small fortune. I sure hope I don't have to replace more than the O2s and the speed sensor #2. My wife is already questioning whether it is worth it.


1. A wife can be replaced.
2. No - I didn't spend all that much, up until the CAT which was about $240.00 installed.

Does Joisey have a limit on what you gotta' spend to cure your ills? Merryland lets you off the hook for a two year pardon if you spend at least $450.00, which I did. So I could have failed for the fifth time & still be allowed to spew forth fumes in the interim.

Ron ( Thanks for the three CATS, Subaru!).

It's been my experience that due to CA emmissions rules, Subaru has to over-do it when it comes to cats. My WRX came with one in the up-pipe, one in the down-pipe and one in the mid-pipe.

I've now got only a single hi-flow cat in the mid-pipe, and even at the high altitude (makes the car run rich) I still pass smog w/ flying colors. 'Course they only do a simple plug-n-play OBD-II test here.

I'll bet two new hi-flow cats before the Y-junction in the SVX's exhaust will work better than the 3 old ones by a lot, and free up a little power. At least that's what I'm planning for my SVX... in addition to a true 1.25" dual exhaust and twin mufflers.