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Discussion Starter · #1 · (Edited)
Long story short. My car(96 cougar) stopped running the other day and I'm not to sure about the cause. I've replaced all the plugs(was throwing misfire codes) because some were broken, but this doesn't seem to be related. It tries to start and will run for a few seconds if the pedal is floored. Tt is getting spark and fuel.

I've had two mechanics tell me that it sounds like a collapsed muffler which just seems a little far fetched because it has dual exaust. So I took a hammer and gave the catalytic converter a smack. I was bewildered when the car now runs for almost a minute with it floored.

I can hear some tinking sounds, like twigs or loose metal in the exaust would make, coming from the front end but the car hasn't been sitting and it just lost power on the road. There were/are no other noises to indicate what the problem might be.

My questions are:
Is it possible for the catalytic converter or mufflers to become plugged by rust/internal breakage enough to hinder the exaust enough to cause the engine to choke itself?

Has anyone else ever experienced similar problems?

I've read that lots of people just cut them out and replace with strait pipe. Are the sensors on it just to monitor emissions? Can they just be cut out off the picture completely(wires snipped and tossed)?
 

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Yes, it is very possible for a catalytic converter to get plugged up. In fact I had one get plugged in a Firebird Formula and strand me on the highway.

Your car has three catalytic converters (assuming that it has the stock "dual exhaust"). It has two converters that are practically bolted right to the manifolds. There is a third that is right where the two downpipes "Y" into a single pipe. It is illegal for a muffler shop to replace the converters with straight pipes so it is difficult to find one that is willing to do it.

As far as sensors and it running. Your car has 4 sensors. two in front of the converters and two after the converters. The two in front of the converters measure the exhuast and tell the computer to adjust air/fuel ratio. The two following the converters just tell the computer if the converters are there or not. They do NOT make any adjustments to the way the enginen runs, though if the converters aren't there they will throw a CEL.

To answer your question. The first two (one per side) are needed for the car two run. the second two (one per side) are not need for the car to run. you can get a chip that shuts off the rear two sensors so you won't get a code.

edit: Oh yea, and welcome to the threads! :D
 

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Do you have dual exhaust, or the factory exhaust/factory like setup?

I could see one bank being clogged causing the car to not run, ahead of the third cat that is.

If you have Factory exhaust you have a common cat in addition to the two individual ones on each downpipe from the manifolds, then single pipe to the rear where it splits to two mufflers. I agree it probably isn't a single muffler, the other leg and muffler could handle it with only slightly degraded performance, but if it is before it goes to one pipe or the third cat itself that is clogged it can cause your car not to run.

Sounds like it won't even run well enough to do a vacuum test on it to see where the restriction might be though. holes can be drilled in the pipes and vacuum checked, I went through this with my 79 Mercury Zephyr, but that turned out to me something else that acted exactly like a blocked exhaust (the pin that holds the distributer gear on sheared, so it was in correct time part of the time, out a few degrees others, or 180 out, wasn't much fun to drive).
 

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Discussion Starter · #4 ·
Thanks for the info, and the welcome :D

I already have a shop that is willing to do it but he said he didn't want to mess around with the sensors and getting them to work. I'mnot to concerned with it throwing a code, I'm already used to the orange glow. Yes, it has the three cats and the fake stock dual exaust.

The first two sensors are mounted on the exaust manifold correct? The second ones are mounted on the cat? So can you just remove the plug from the second sensors, strap them somewhere safe and pull the rig off and all will be well?
 

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Well, technically, the first two are mounted just after the manifolds but very close to them The second two just aft of the cats. you can just not use the second set of O2 sensors and let the wires hang down (there are plugs on them)

I plan to replace my downtubes (and cats) this spring with downtubes that don't include the cats. They will (of course) have bungs for the first two O2 sensors, but not for the second set. I have a chip that shuts off the second two sensors.
 

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Just out of curiosity.. has your car ever been puffing smoke, say.. from a stoplight or after idling for a while?

If the CEL would bother you, you can investigate MIL eliminators (give search on this forum, plenty of hits). But if your willing to dump the cash, a chip would kill several birds with one stone.
 

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I'm curious about the statement "I'm used to the orange glow" what is it glowing for? Have you had the codes checked?
 

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timb said:
I'm curious about the statement "I'm used to the orange glow" what is it glowing for? Have you had the codes checked?

ah.....theres your sign.
 

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I just dealt with the exact issue you are dealing with. The car will crank and start, but it won't really run very well. It will stumble and you have to play with the throttle to get it to stay running but it won't rev up high and it'll die soon after. Sometimes it even takes a while to get going. I also had tons of misfire codes, all but one cylinder in fact.

The problem turned out to be three things combined. First, the exhaust was completely plugged up. This is what was preventing the car from starting in the first place. Second, both coil packs AND the plug wires were bad, causing misfires on all the cylinders. My theory is that the plugs/coils were going bad for a while and then over an extended period of time, the unburnt fuel entering the exhaust because of the misfires finally caused the two front cats to destroy themselves and break apart. This clogged up the exhaust and prevented the car from running period. What I did is dropped the exhaust completely and was able to start the car. All the oxygen sensors are in the exhaust pipes; none are in the manifolds. This means that the car won't be running closed loop if you leave the exhaust off. What I'd do is lower the exhaust and punch out the broken cats so the whole system is hollow, then put it back on. You'll also have to address the misfire issue which is probably the result of bad plug wires. But for sure your cats are broken up. You losing power, the exhaust glowing red, those are the tell-tale signs. I hope you didn't run it like that for very long or you could have damaged the motor. That's way too much backpressure and headgaskets don't like it.
 

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Discussion Starter · #10 ·
Sorry about the late reply.

The CEL is on because it is misfiring on a few cylinders(replaced the plugs, a few of them were broken) and one of the O2 sensors is dead(throwing a malfunction and heater error on bank 1 sensor 1) along with a few other codes(running lean in one bank and rich in the other, gonna clean the MAF sensor, ect.)

I plan on cutting the exaust off tomorrow, so thanks for the info, it was very reasuring. I've never had it "puff" smoke, it has a pretty even flow. I'll be sure to post the results of my efforts for future reference for others that are having the same issues.
 

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if you suspect exhaust blockage you can remove the 02s upstream and start it up.If it runs better then it could tell you something. high idle it also all the way to 5000 or the revs that your car was missing at

edit: i didnt see that you had said that the cats were glowing lol if they glow they are melted for sure
 
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