Alexlepro

I just bought a 1984 944 in very good condition. The car looks and runs great and has no mechanical problems but I just took it to smog and it failed miserably (in CO at least). Well here are the results:

15mph:
RPM: 1757
CO2: 10.5
O2: 0.0
HC: 264 (Max 135)
CO: 6.65 (Max .83)
NO: 202 (Max 1136)

25mph:
RPM: 2801
CO2: 11.5
O2: 0.0
HC: 247 (Max 110)
CO: 5.00 (Max 0.63)
NO: 659 (Max: 966)

The car is stock and in California. When I got it 2 weeks ago it obviously had a crack in the exhaust. As it had happened to previous 944's I have owned there was a nice crack right before the catalytic converter. In my last 944 I welded the crack and everything was fine so I did the same to this one before the test. Could it be the cat that needs replacing? Other than that, the car runs great. What could be causing these high numbers?

SoCal Driver

Running rich. Check the vacuum lines to the fpr and damper. The rubber fittings harden and leak. The plastic tubing also imbrittles and cracks. Check the fuel pressure after fixing the vacuum lines.

High HC and low NOx is rich. Reversed and it's too lean. Could have ruined the CAT running too rich. A bad O2 sensor will throw the DME into a rich mode too.

ibkevin

Alex, where in SD are you?

Alexlepro

ibkevin, I'm in North County, in Vista.
Thanks for the help so far, i'll look into a vacuum leak.

nickg

change the oil, put fresh plugs in and look for vacum leaks. Get the car really hot and measure Voltage at the o2 senser...it should vary from .00-.9 volts with rapid(about 3 times a second or better) cycling. if not replace the o2.

ibkevin

I had to replace my O2 sensor when I first brought the 951 from Wisconnsin to pass smog.

If you think you need to swap the cat, I have one pending sale, just let me know.

Alexlepro

I have a few questions. First, how to I go about checking for vacuum leaks. I was told to spray starter fluid on the lines when the engine is cold but it seems there must be a better way. Also is there any way to tell if a catalytic converter is bad? Visual inspection? If so, what are some giveaways?

mavfan

i would say your car is in desperate need of a new cat. my 944 was horrible like that, and with a new(used) cat it passed perfectly

ibkevin

How did the O2 sensor test go?

unsigned

I just passed IL emissions with flying colors today. Well, the gas cap failed, but the sniffer test was a joke.

mavfan

i dont understand that part, where they hook that think up to your gas cap? can anyone explain?

KuHL 951

They check the cap for a tight seal on a machine to make sure gas vapors go back through the charcoal canister and not vent to atmosphere.

unsigned

yep, the rubber part on my cap was all cracked. I guess I wan't too suprised, though it passed last year.

Alexlepro

Alright, just checked the O2 sensor, it always reads .45 volts without changing so I guess it's shot. I'm happy it was something simple. We will see at the smog tomorrow.

nickg

that it is...make sure the car was HOT...