Short of shoving it off a cliff for a movie stunt, I need some serious advice.

Car is a great running (99 mph 1/4 mile, first time at the track with a stick) 95 LT1 obd1 105k miles, with I assume no performance mods. Purchased in Nov over in Reno, Nevada, finally getting around to trying to license it in CA.

First time, it only failed the idle test, it got 123 co's and the max is 100. Smog shop said to run a bottle of "Guranteed to Pass" through it. Check. Shop also said the cat might be getting old.

Second time, it only failed on the idle test, it got ~125 co's, max 100. Smog shop (different one) said to change the O2 sensors and the PCV valve. Check. Also changed oil and put in Bosch Platinum 2 plugs all around (~3 hours, 2 sore arms, a crinked neck, etc etc.)

3rd time, it failed all over the board, both idle and 2500 rpm, idle got ~150 co's. I can get the actual results if it would help diagnose. Shop said it's running too rich, and "furthe diangosis is needed." At $78 a hour, of course.

How can I lean it up? Is the cat possibly bad? If new cat is recommended, what's the size of piping? (I think it's 2.5", not positive though.)

Is there any easy way to lean it out for the test?

Thanks!

 

ok, ummm which care are you talkin about, and are there ANY mods on the 3rd gen.

As Long as the motor is running good, a brand new cat, and 2 bottles of rubbin alcohol, 180 temp thermo and driving it on the roller will do the trick.

 

I'm pretty sure that it's 3" piping, but not possitive. How were the HC levels? Also, when my cat went bad it rattled a lot and I was told that that is a sure sign of an empty cat. Sure enough the guy was right about the rattle.

 

2 Bottles of rubbing alcohol down the gas tank?

3rd gen has LT headers, !maf screen, that's it.

 

try changing the Egr, cause i was having the same problem as you

 

Run some fuel system cleaner, change cat, check EGR

 

What are the values for HC and NOx? That might indicate whether its the cat, or its running rich.

 

Because it was failing so bad AFTER the plugs and O2's were changed, i would think its something to do with the install of the new plugs or bad O2's since it shouldn't have gotten worse after those two are swapped out... Do you have anyone who can scan it for you?

 

I cheat to get around the sniffer.....AIR pump, 8 feet of rubber line....and a little nipple welded into my exhaust right before the muffler...its enough to dilute it down so I can pass ...

355ci Lt!
hotcam
p600b
no cat
PCM4less tune

 

Test 3 Idle -
HC = 147, allowed 100.
CO = 1.16, allowed 1.00

2370 RPM -
HC = 18, allowed 130
CO = 1.35, allowed 1.00

Test 2 - 6 days ealier, with old plugs and crudded up o2 sensors

Idle -
HC - 123 / 100
CO- .71 / 1.00
2500 rpm -
HC - 30 / 100
CO .40 / 1.00

Is it possible the car is running in open loop? How can I check if it's going into closed loop?

It's obd 1, with no check engine light, should I still get it scanned?

I'll definitly get an EGR valve for it.

I've conisdered the smog pump idea, I've got a "spare" one from my L98 kicking around... Just not sure how I'd mount it up to the block.

Another detail - the drivers bank O2 sensor was black from soot, the riders side was clean, but I replaced both anyway.

 

Sounds like its running excessivley rich on the drivers side. Might be the O2 sensor, but it might also be a problem with exhaust leaks before the O2 sensor, or misfires on that bank.