Catalytics Converters

[MikeSomeone]

My brother has an 86 Pathfinder. It has issues with power. When you push the gas pedal down it acts like it wants to stall then it shifts hard and goes forward. Could this be that the catalytics converter is clogged or partially blocked. I thought maybe this would create too much backpressure which is why it has this problem. It makes sense to me. What causes these to clog? Can they clog from just age or is it something else that creates this problem?

[curtis73]

A properly tuned engine will most likely never clog a catalyst. What clogs them is unburned fuel. Catalysts are supposed to deal with just exhaust gasses, not unburned gasoline, so when gasoline vapor hits the hot catalyst it just sticks there like glue eventually clogging it. A clogged catalyst shows up as things like melted carpet on the floor, a spot of dead grass under where its parked, and poor top-end performance

I highly doubt that the catalyst is the problem. A blocked catalyst would be worst at higher RPMs and throttle positions. There are a few dozen other things that could be causing the problem, but I doubt its the catalyst. The first places I would look are:

TPS, throttle position sensor
FPR, fuel pressure regulator
plugs, wires, cap, rotor, coil... ignition troubles almost always cause stutters like you describe

[psychopathicdude]

Or when the catalyst disintegrates from repeated backfiring from a rich idle setting and pieces of the catalyst come flying out the tailpipe... that's a good indicator of a systemic malfunction.

Your problem sounds more like hesitation due to ignition, perhaps a faulty advance, maybe a slipped timing belt, I don't really know pathfinders, but the symptoms you describe don't sound like the Cat-Con.

As Curtis said, a clogged Catylverter usually manifests as excessive backpressure at mid to high RPM... if it was clogged enough to cause hesitation at idle, you'd never get it off idle...

[MikeSomeone]

The truck runs fine at higher rpms this just happens when starting from a stop or from a really low speed. We'll check out the ignition systems. I think I might have seen someone in another forum describing what seemed to me kind of the same problem and they said that their O2 sensor was bad or clogged or something. THis could be totally inaccurate but could it be a possibility. Keep in mind I don't know that much about cars, im only 16.