951 trouble passing emissions!

europsh · 07-11-2010, 02:42 PM

Just got back from a smog test here in CA, and my 87' 944 turbo failed fairly miserably. A few details on the car: 90k miles, 8k miles on a freshly rebuilt engine from Lindsey Racing, cored cat, just ran some seafoam through the tank and vac lines.

Test results
@15MPH
HC 115 (81 max)
CO 0.81 (0.52 max)
NO 2269 (689 max)
02 0.78%

@20MPH
HC 103 (63 max)
CO 0.61 (0.43 max)
NO 2078 (730 max)
02 0.63%

I realize the cored cat is likely a big contributor to the problem, but I've heard these cars can pass w/o cats. Anyone know if these numbers are indicative of a particular problem (plugs/ 02 sensor / etc), or any advice on e-test tips and tricks?

Thanks-

bw993 · 07-11-2010, 02:48 PM

You cannot pass Calif. emissions without a CAT. You need the CAT to pass NO, since the limits were lowered in 2010.

nynor · 07-12-2010, 06:55 PM

cat and a bad O2 sensor, perhaps, vacuum leaks.

89-944NA · 89-944NA's Garage

Replace your cat, your HC numbers are unburned HydroCarbons, NO is carbon monoxide, and the NOX numbers are Oxides of Nitrogen, all are what the cat is supposed to neutralize. May as well replace the O2 sensor while your at it, as the "somewhat" established industry figure for their life is about 60,000.

Rogue_Ant · 01:10 AM

We've been able to pass Colorado emissions without a cat...
Your HC are not too far off, CO2 is just a function of HC. But your NOx definitely needs some work.

To pass, you are going to need to pull timing and fuel... Not sure what your using to tune.
And even then - I had to make a emissions-only chip to get a reasonably stock car (without cat) to pass.

-Rogue

europsh · 07-16-2010, 07:39 AM

Thanks for the advice, all. I'm actually having a new cat (magnaflow 36106) installed as we speak. Hopefully that will be the magic ticket, although I'm slightly skeptical that we'll get all three metrics under the CA standards with just a cat. I'll do a quick check over for vac leaks as well -- all the hoses are brand new, are there any components that tend to leak that are attached to the vac lines that I should check particularly thoroughly?

I'll post results when I head in for a re-test...

kdjones2000 · kdjones2000's Garage

The Idle Control Valve (ICV) has been known to leak. It is located underneath the intake manifold.

Good luck, Keith

nynor · 07-16-2010, 07:19 PM

huh. that's cool. are they going to be installing the magnaflow cat on a stock exhaust? cost?

Quote:

Originally Posted by europsh

Thanks for the advice, all. I'm actually having a new cat (magnaflow 36106) installed as we speak. Hopefully that will be the magic ticket, although I'm slightly skeptical that we'll get all three metrics under the CA standards with just a cat. I'll do a quick check over for vac leaks as well -- all the hoses are brand new, are there any components that tend to leak that are attached to the vac lines that I should check particularly thoroughly?

I'll post results when I head in for a re-test...

europsh · 08-04-2010, 07:36 AM

Finally got around to re-testing the car! Good news: the HCs and COs are extremely low, but the NOx are still high. I passed the 15mph rolling test on all metrics, but the 25mph exceeded the NO limit (1010ppm / 730ppm MAX).

I'm thinking my next best bet is a new O2 sensor? From the numbers, it appears as though the engine is running a little hot (lean). Thoughts?

Thanks!

europsh · 08-04-2010, 07:38 AM

Quote:

Originally Posted by nynor

huh. that's cool. are they going to be installing the magnaflow cat on a stock exhaust? cost?

Yep, they just hacked out the old one and welded in the new magnaflow unit. Cost was an hour of labor, whatever that tax may be at your local exhaust shop

Litesonic · Litesonic's Garage

I had great success with running just a gallon of E85 at the refill light (so you still have about 2 gallons left) to get the NO low.

Now if I could just get mine to go the other way (lean).... I am still over on HC and now CO. I had a new Walker cat put in. But that failed worse than the stock cat (surprise). I have an actual mechanic (not me) looking it over now and seeing if it is an injector/compression thing that is causing it to not make it.

Best of luck to you.

DannoXYZ · 04:29 PM

Quote:

Originally Posted by europsh

Finally got around to re-testing the car! Good news: the HCs and COs are extremely low, but the NOx are still high. I passed the 15mph rolling test on all metrics, but the 25mph exceeded the NO limit (1010ppm / 730ppm MAX).

I'm thinking my next best bet is a new O2 sensor? From the numbers, it appears as though the engine is running a little hot (lean). Thoughts?

Was it a 3-way cat you got? Was it CARB approved with ID#? There's a lot of them that are 2-way cats that only work on HC/CO but not NOx (there's a lot of states that don't have NOx requirements).

What are your numbers compared to the previous test? I've been able to reduce NOx a lot by dialing back the ignition a little. Although I'm still leary of the new cat because the last time I swapped in a cat for a straight-pipe, all three numbers were reduced significantly.