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Old 02-29-2016, 12:44 AM
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Is my cat shot?

I've got a 2000 WJ with 4.7 and 148,000 miles. I was driving along one day when I suddenly got some surging in the vehicle and "bucking". The engine seemed like it would only run up to 3000 rpms max. I stopped and shut off the engine, restarted it, and it seemed a bit better, allowing me to hit the factory throttle cut at around 5500 rpms.

I did the key dance to pull the codes: 0442, 0443, 0645, and 0320. I've had chronic problems with 0442 and 0443, no biggie to me. 0645 might have been from this summer when my a/c compressor clutch died. I replaced that clutch. But the 0320 was new to me. So I read the forums, and decided I would replace both the crank position sensor and also the cam position sensor. MOPAR parts for both, from the dealer, as most forum people insisted on. Had to remove the starter to get at the crank sensor, kind of a pain.

Got everything back together, fired it up, and the engine sounded the same way--chugging along at idle, severely limited power, sounds like it's missing on half the cylinders. Except no new codes.

So I go out today and let it idle for 35 minutes while I check out other engine noises with a stethescope. I figured it must need more time to generate a MIL. No light. I used a laser scanner to take heat readings of the exhaust manifolds, and piping before the cat, post cat, and post muffler. The pipes around the cat and muffler are all right around 220*F. I bang on the cat with a rubber mallet, but no noise is coming from there. So then I decide to take it for a ride and put a real load on the engine. I must say that the problem has seemed to have smoothed out compared to when I first started up the engine, but it's obviously still missing and lower on power than before. As I'm driving, it's really windy and I get a distinct sulfur smell so I figure "yep, it's the cat". I abuse it coming home the last mile and drive up on ramps, grab the laser gun and this time I measure 420* at the pipe right before the cat, and 880* immediately after the cat!!

So I figure it's gotta be the converter, but I still have no codes. At one point during the 35 minute idle time, I swear I saw 2 tiny embers come out the exhaust pipe, but I'm not entirely sure--it was so damn windy here today, but that's gotta be what they were.

With a glove on, I was able to completely cover the exhaust tip and make a pretty good seal, which I didn't think I should be able to do.

What's everybody's thoughts?? Is this a clear cut case of needing a new converter? BTW, I don't remember seeing any additional converters. Just this 1 right in front of the muffler. There's an O2 sensor directly in front of the converter, and 1 O2 sensor right after it. Or does this need further diagnosing with a scan tool to see if something like a new timing chain could be needed?

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Old 03-02-2016, 08:43 PM
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Re: Is my cat shot?

Not sure about the normal cat temperature, but it should be hotter then before the cat, since it burns residues in the gasses.
Sulfer smell could be due to a wrong air/fuel mixture as well. I would put it on a scanner with live data and check the MAP and the fuel trims (STFT and LTFT). The MAP you check with engine off, but ignition in on. The pressure should be close to the local barometric pressure.
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Old 03-06-2016, 12:18 AM
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Re: Is my cat shot?

Thanks Frango!! I ended up taking it to the dealership--the first time I've ever taken any vehicle to a dealership.

All they could find was a misfire in cyl 1, which the check engine light showed about 5 miles before I arrived at the dealership. They said I needed a new coil. I didn't know they just crapped out like that, especially when I replaced them 2 years ago with ones from AutoZone.


Anyway, I asked them to diagnose some mechanical noise for me that was troubling me. To me, I always thought it sounded like it was coming from the timing chain, with noise coming from the PCV valve when listening with stethescope. Noise went away when revving anywhere above idle.

Dealership stated it was timing chain noise, AND #1 piston skirt noise. They said not to panic about the piston skirt noise, and for timing chain, just change oil religiously at 3000 miles to keep the chain lubricated and prevent it from getting gummed up or sludged up. Now I'm researching piston slam noises and trying to get a feel for longevity on this engine.

I never heard the piston noise until I drove it away from the dealership. I stopped at a parts store to pick up a new coil and change it out before I drove home. That eliminated the horrible piston noise I heard. Still.....if that was a piston skirt hitting the bore of the cylinder, that can never be good in my book, although the dealer seemed to think otherwise telling me they've seen plenty go 50,000 miles.
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