Busted Catalytic Converter?

[rachwalj]

I swear I searched heavily on this and have an inkling of what the problem is/may be, but I want to check with the experts here before I toss more $$$ at the car.

When I first start the car, (after letting her warm a bit)I start driving and before I reach full temperature, there is this noise that comes from under the car. It does not have a pattern. Kind of sounds like broken glass in a coffee can. Eventually, it almost completely subsides (except hard acceleration). It is aweful until the car warms up.

I have read several posts from many different types of cars that this could be the element inside the cat is broken. I don't know if it was ever replaced.

Does anyone have any experience with this? I am going to bang on it tonight when I get home to listen for broken stuff.

Thanks in advance.

[SoCal Driver]

Sounds like the ceramic in the CAT is busted.

[will944]

Yup....got some loose stuff in the cat area. Mine had the same problem....so I just emptied it all out....whoops....

I found a replacement on Ebay for $85. Used but with low mileage....worked great.

And no...there is no advantage to removing the cat in an NA car....no 20HP like some idiots claim. It did NOTHING for my performance.

[mambodave]

Not sure if your stat requires emisions testing..

But I have a cat bypass pipe Ill let you make me an offer on.

[s928s]

off subect onto you signature line, you noted that the heat was always on". i may have solution for you, just ran across the same thing on my 87n/a. did the new t-stat, low temp fan switch, checked heater valve and vac lines, checked blend door opperation, all ok....found the air temp sensor clogged with a lint ball. seams that when it registers no heat on the temp sensor it open the blend door even if you have it set on cold unplugged the unit and removed to clean it out, while unplugged the heater went to full heat, with it cleaned and working again the system went back to normal temp...just a though for something to try !!

[gearhead290]

If you don't have to have your emissions checked then take the cat. off of the car and ram a metal rod into the cat to break up all of the junk inside. Then dump it all out and put it back on the car. BUT then the car will no longer meet emissions so if your state checks emissions then you have to have a working catalytic converter.

[Brian J]

Originally posted by will944

And no...there is no advantage to removing the cat in an NA car....no 20HP like some idiots claim. It did NOTHING for my performance.

My '84 944NA failed epa test becasue the PO removed the cat and put in a $20 glass pack. When it was replaced with OEM cat the performance actually went up. My assumption is that engines are designed with a specific back pressure in mind. When any of that is disrupted it creates a real "distubance in the force".

[rachwalj]

Originally posted by s928s
off subect onto you signature line, you noted that the heat was always on". i may have solution for you, just ran across the same thing on my 87n/a. did the new t-stat, low temp fan switch, checked heater valve and vac lines, checked blend door opperation, all ok....found the air temp sensor clogged with a lint ball. seams that when it registers no heat on the temp sensor it open the blend door even if you have it set on cold unplugged the unit and removed to clean it out, while unplugged the heater went to full heat, with it cleaned and working again the system went back to normal temp...just a though for something to try !!

The problem that I had was this little plastic clip that holds the heater valve shut. It very commonly breaks and the valve gets stuck open. Very easy fix... Thanks for the tip, it might help someone else.

[rachwalj]

Any notion of removing the cat or "bypassing" it, will get you rejected in seconds flat. The bast@rds here white glove you like mad. They put the car on a dyno and run it at 30 MPH for like 45 seconds. They do this three times. It has to pass all three.

Whats worse, is I personally know the guy that does it and he said my emmissions were "so unbelievably" bad, he couldn't let me go. His point was that something was seriously wrong and it was/is probably affecting performance.

So I have a new O2 sensor, and I guess I am looking for a cat now.

Thanks

[338WIN]

My 84 Buick Park Ave passed emissions without the cat(109,000 miles on it). It still has a carb, no injection system. (I bought it in a county that does not require emissions testing. I live in a county that does.)
It would seem to me that if Wilk's chip eliminates the O2 sensor then adding the chip and eliminating the cat shouldn't affect performance at all. Eliminating the cat while the DME is looking for it sure seems like it would confuse the fuel delivery.
BTW, the rolling sofa with six people capacity, electric moonroof, unparalled air conditioning, self adjusting rear ride height, cavernous trunk and relatively anemic V8 is a great stablemate to the 944. $1,000 bucks and worth every penny. Even better would be a mid '90's Cadillac Fleetwood with the LT1 drivetrain. $5-7K for a good one.

[rachwalj]

OK This is a good one. Check this out. I had numerous opinions on this and almost everyone was convinced that the cat was toast. I even broke down and brought it to a mechanic and with a test ride, he agreed.

So I decided to change the belts (power steering and alternator). The previous owner "hacked" this car so poorly. The P/S pump was held on with a bolt that was the wrong size (and loose) and the bracket on the bottom is some random piece of metal with holes drilled in it. I consequently had to drill more as the wrong belt was on the P/S pump.

THE NOISE IS GONE. She is quiet as can be. I did a double take. I tried for like an hour to make sense of this. It must have been so loose, that is was rattling around especially upon accelleration.

The hacks on this car are so numerous. I have fixed at least 7 so far. Some really interesting stuff.

[Tishabet]

Hey rachwalj, where in the bay state are you located?

[nige944]

Originally posted by rachwalj
Any notion of removing the cat or "bypassing" it, will get you rejected in seconds flat. The bast@rds here white glove you like mad. They put the car on a dyno and run it at 30 MPH for like 45 seconds. They do this three times. It has to pass all three.

Whats worse, is I personally know the guy that does it and he said my emmissions were "so unbelievably" bad, he couldn't let me go. His point was that something was seriously wrong and it was/is probably affecting performance.

So I have a new O2 sensor, and I guess I am looking for a cat now.

Thanks

My experience in Taxachusetts wasn't too bad they failed me first time, but i was so close the second time they came back in the waiting room and asked me what i had fixed, I gave him a small list (AFM, O2, & tune-up), he left the waiting room and came back 5 minutes later with a pass.

You only have to spend about $250 or so with a "named" emissions garage in repair costs and they let you off with the emissions test anyway. (which kind of screws the home mechanic)

No idea what they did to let me pass though :>

[rachwalj]

Originally posted by Tshabet
Hey rachwalj, where in the bay state are you located?

I am in Uxbridge, but I work in Waltham. I am hoping to take her to work once a week, but I have to get to the bottom of the high temp reading.

I still have to put in the O2 Sensor, I have done the tune up already.

[Eli K]

Below are my readings before and after swaping the CAT and O2 sensor. I found a universal high flow catalytic converter for under $50 on e-bay (make sure you e-mail the person before buying and tell them you have a 944, p-cars take a smaller version with 2" openings), and had a local muffler shop put it on for $100.

Before replacing CAT and O2 sensor

AT 15 MPH
________LIMIT _____READING
HC ppm __130________ 146
CO % ____.73________ 1.39
NO ppm __1010 _______1313

AT 25 MPH

_________LIMIT_______ READING
HC ppm___ 126 __________157
CO %_____ .77 __________1.37
NO ppm ___0919________ 1399

AFTER REPLACING CAT AND O2 SENSOR

AT 15 MPH
__________LIMIT_____READING
HC ppm_____130______19
CO % _____.73______.04
NO ppm____1010______74

AT 25 MPH

___________LIMIT_____READING
HC ppm _____126________23
CO %_______.77________.04
NO ppm_____ 0919______ 36