: clogged Cat?

10-02-04, 11:41 PM
My gas Mileage has been bad of late (11-13 mpg city) It has been dropping ever since I had a coil pack and fpr go bad on me (at the same time) Anthony Cipriano would probably remember that, anyway my cat overheated a couple of times and I was wondering, what are the symptoms of a bad/blocked cat. I'm not sure what else it could be.
oh, and no codes

Night Wolf
10-02-04, 11:51 PM
the CAT overheated?!?

My cat was bad.... on the 4.9

my gas millage sucked... I was getting about 12 around town and 19 on the highway.... the same millage I get with the '79 :rolleyes2

acceleration wasn't as good, on the highway she felt sulggish

it would idle rough... the 4.9 normally idles rough, but I mean this was shaking the whole car

over about a month it stalled out on me 7-8 times... it would be when I would come to a stop at a light... I would noticve it becuase the dash lights would come on, I would hit the gas and nothing happened, or if I pumped the brake pedal, it would get firm....

... in my case, the cat was actually broken inside, not clogged.... so when idling you would hear a loud annoying rattling sound... when we finally took the cat off, you could look thru it... then shake it up, and not see thru it.... who knows what that was doing for backpressure on the exhaust...

few other symptoms... but that is what I was getting.... ever since we changed the cat, all those problems are now solved.....

10-03-04, 07:53 PM
My cat always turn flamin red i mean it would burn a piece of paper if i stick it to it.
Somthing wrong with my fuel injector, every time i replace the fuse it would burn out and causing my cat to overheat.
i also have a horrible gas mileage at about 5-6 mpg. she also doesnt take off untill about 5 second even if i step the pedal to the metal. Could it be the spark plug or somthin?
someone please help me.

10-03-04, 10:01 PM
try checking the coil packs that was my problem a coulpe of times.

10-03-04, 10:28 PM
What is coil pack?


10-04-04, 12:09 AM
I shoulda asked first what model/year is your car

10-04-04, 11:01 AM
The coil pack is the 4 coils sitting on the rear cam cover (passenger side). Spark plug wires are conneted to them.

10-05-04, 03:31 PM
anyone else have any ideas about my problem

10-05-04, 04:11 PM
CadiJeff -

If the cat is overheating, it sounds like fuel is burning in there. If unburned fuel gets into the exhaust, it can burn up when it hits the hot catalyst and heat up the cat even more. Assuming that's the case, why is the unburned fuel getting to the cat? It could be a bad or clogged injector, bad fuel pressure regulator, bad oxygen sensors, bad mass air sensor, etc. Does the exhaust smell at all like unburned gasoline when the engine is at full temperature (10-15 minutes)? Overheating will eventually destroy the catalyst, so if the cat is already hosed, that could be part of the problem.

94CaddyConcours -

Search the forums for "pcm codes," go through the process of retrieving the codes, look them up using the first link in the Northstar forum (OBD codes), and post the results here. It may say exactly what systems are failing, or it may point to further troubleshooting steps. One way or another, that's the place to start. Post those results and someone will be able to help you further.

May the Schwartz be with you... :D


Anthony Cipriano
10-05-04, 04:14 PM
anyone else have any ideas about my problem

It certainly could be the cat melted from your earlier problems. You can take the oxygen sensor out and fashion a fitting to screw into the hole to use a pressure gauge to measure the exhaust backpressure. 1-3psi is probably fine at a slightly fast idle - anything higher indicates a plugged/melted cat.

Is the car really sluggish at full throttle? Usually if a cat is plugged/melted then it really starts to hurt the full throttle performance as the engine revs up towards a shift. If it is plugged badly the engine will feel like it can't make it to the shift point at full throttle.

10-05-04, 10:54 PM
not too terribly bad but it is noticable, I have niticed it being a slight bit more sluggish than it used too be especilally when I accelerate from 4th gear it dosn't downshift to third as quickly as it used to this has created a couple of nervous moments on the highway. I also have noticed recently (since it became cooler and the A/C is off) a slight exhaust smell in the car when stopped. I checked the way the exhaust exits the mufflers and it dosn't seem to be as smooth as before.

If it is the cat would straight piping it as a temporary solution throw any codes?

Anthony Cipriano
10-05-04, 11:24 PM
No codes should be caused on a 94 if you replace the cat with a straight pipe.

10-05-04, 11:39 PM
ok are there any other concerns that would be caused by removing the CAT

also all this could be the result of a 182k mi engine

Anthony Cipriano
10-05-04, 11:45 PM
No. I wouldn't hesitate to try it on an engine with that many miles. It wont hurt anything.

10-05-04, 11:52 PM
would it help?