When a catalytic converter goes bad... - DodgeTalk : Dodge Car Forums, Dodge Truck Forums and Ram Forums
 
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#1 Old 02-12-2011, 10:34 PM
RegularJoe
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When a catalytic converter goes bad...

I've got a '95 B2500 w/ 3.9L, with 180,000 miles. She's a homely old girl, but I taught three kids to drive in it, and have taken it everywhere from Big Bend Nat'l Park to Manhattan, and I love her. I've had the odd problem -- several starters, a couple of water pumps, wheel bearings, more brake shoes and brake pads than I could count, tranny rebuilt twice -- but the engine itself has been a rock -- I've never even had the valve covers off. And I'm hoping to keep it that way if I can.

I was having progressively worse engine sputtering over the last couple of weeks -- one day it wouldn't even start -- and it finally gave up the ghost last week, and won't run at all.

My first thought, considering the way it got worse, was that it might be my catalytic converter, so I removed it (it was a universal-fit cc, I put on probably 6 or 7 years and 50,000 or so miles ago, and the symptoms this time were very similar to that time). It does seem bad -- feels like there's 2 or 3 chunks of concrete in it, that shift around when I shake it or rock it back and forth. Seeing that it was in bad shape, I thought "AHA, it'll probably start right up now!" Suffice to say I wouldn't be writing this if it had.

I used starting fluid to see if it was spark or gas, and it didn't make any serious sign of firing; every three or four seconds I'd hear what sounded like weak backfiring (which was probably just "firing", but with the CC off and open pipes right under me it boomed more than it would otherwise). So I assume it's probably ignition, and I've got a rough plan of action to troubleshoot that (although there's a GOOD chance I'll be back here again for advice). I used the old "screwdriver in the spark plug boot and look for a spark" trick; it sparked, but the spark looked pretty anemic to me. But what do I know? I haven't done this sort of troubleshooting in years. Anyway, I bought the Haynes book today, and will start testing coil, distributor position sensor, and various other electronic parts tomorrow.

But I can't escape this nagging thought that the back-pressure from a bad CC might have done some mechanical damage -- maybe caused the valves to be harder to move than they should have been, and that the resistance might have busted the timing chain. Is there any reason to be concerned about that? Or maybe the CC wasn't really causing problems yet, and it was JUST the timing chain; will it ever cause the engine to sporadically run badly? It doesn't seem like it would be sporadic if it was the timing chain, either jumping a tooth and eventually two teeth, or getting looser over time until it broke. And how would I go about figuring out if the chain is busted? I thought about looking into the valve cover through the PCV valve hole, to see if the rocker arms are moving, but there's a baffle. Does anyone know of a way to tell without pulling the valve covers? I'm hoping you guys are going to tell me I'm crazy to even suspect this. I'd much rather see a shrink than change a timing chain.

One final question, as long as I've got people's attention: considering the description I've given, if you were going to guess what the problem is most likely to turn out to be, what would your top two or three guesses be?

Thanks very much for any words of wisdom.

Last edited by RegularJoe; 02-12-2011 at 10:52 PM.
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#2 Old 02-12-2011, 10:48 PM
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Oh, some additional info; I used the "on-off-on-off-on" trick to get codes. I got 12 (I've run the battery down and recharged it several times as I've experimented, and I think that explains the 12), 41, 45, and 55.
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#3 Old 02-12-2011, 11:25 PM
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180K and never replaced the fuel pump? Check fuel delivery/pressure. If the TC was broken it would die all at once.

Here's a link for codes:

http://www.allpar.com/fix/codes/index.html
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#4 Old 02-13-2011, 06:52 AM
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Thanks for the codes. I have a chart for those, but the info at the links from the page you sent me to appear very helpful. I'll be studying that this afternoon.

And yes, sorry for not mentioning it -- I replaced the fuel pump about 2 years ago, and replaced it again in September. I just pretty much ruled it out when starting fluid didn't get it going; when it went out before, a bit of that in the carb started it right up. Also, my two previous fuel pump failures were preceded by fuel gauge irregularities, although I didn't consider that any real proof that this wasn't fuel pump.

And I understand that once the timing chain broke it would die for good; I just wonder if it could have broken as a result of some other problem, specifically the pressure from the catalytic converter. There was some awful clattering coming from under the van as I pulled it into the driveway the last time (I have poor hearing, and couldn't tell for certain precisely where the noise was coming from). I had attributed that to the CC, but obviously something else is wrong. I just don't want to spend a month troubleshooting electrical stuff, THEN discover that I have to do the timing chain. I'm hoping that this fear is totally unrealistic.

Even apart from this problem, I'm wondering if anyone has any clever idea for knowing if the timing chain is still intact.

As I was typing the above, I had another thought; is there some particular problem that might have caused my general problem that would also spoil the CC? If some sensor was causing it to run, say, too rich or too lean, or to pre-detonate, could that cause the CC to be going out in addition to the progressively worsening idle and eventual death?

Thanks.

Last edited by RegularJoe; 02-13-2011 at 07:19 AM.
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#5 Old 02-13-2011, 10:15 AM
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Compression test would tell you if the timing chain is intact and not jumped a tooth.

Heating up the PCM with a hair dryer may help determine if the PCM board has an issue. Heat it up for 10 minutes and see if it starts.

Have you looked at the ASD (Auto Shut Down) relay yet?

1977 Chevrolet Impala Sedan, 5.0L, TH200, 2.56:1, 106K miles, 37 Lifetime Warranty Parts.
1989 GMC Sierra Extended Cab 5.7L, 5 Speed, 3.08:1, 327K miles, 0 Lifetime Warranty Parts.
1997 Dodge Ram B2500, gone.

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#6 Old 02-13-2011, 10:17 AM
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Usually the CATs die (clog up) around 100K miles. Mine was around 108K miles. Some happen slowly while other CATs just die suddenly. Your symptoms sound very similar to a CAT failure. Even though you had changed the CAT 50K back, the new one might have gone bad too.

One another note, the very first time my ignition coil died on the engine, it displayed the same symptoms too and then died making the van not starting.

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#7 Old 02-13-2011, 10:40 AM
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Quote:
Originally Posted by RegularJoe View Post
Even apart from this problem, I'm wondering if anyone has any clever idea for knowing if the timing chain is still intact.
If the TC was broken, the rotor in the distributor wouldn't turn. Back pressure would work against everything but it's age and wear that finally causes the TC to break. Yes, faulty sensors will affect the mixture that passes thru the CC and eventually cause it to clog. How is the oil consumption on this van?

http://www.aa1car.com/library/exhaust_backpressure.htm

Check the links to CC operation,etc. also.

Last edited by VanMoreSon; 02-13-2011 at 10:57 AM.
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#8 Old 02-13-2011, 01:44 PM
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Thanks for all the suggestions. I'll try the hair-dryer; but I've also learned that a local Advanced Auto Parts can supposedly test the PCM, so I'll try that, too.

The more I think rationally about this, the more the coil seems likely to be the culprit. I'm just about to go outside and start testing things, starting with the coil.

ASD switch -- I didn't even know such a thing exists; I'll look up in the manual and see how to test it. Thanks for the suggestion.

Thanks, all of you. I'll post back tonight and let you know what (if anything) I've learned.
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#9 Old 02-13-2011, 08:29 PM
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Yep, I'm a worse worry wart than any old lady. Timing chain is fine, and so's the rest of the van! The coil primary resistance was a little low, so I changed it; and while I was at it, I swapped out plugs, plug wires, and distributor cap & rotor. Started right up and purring like a kitten -- a tiger kitten at the moment, since the exhaust is off...

Thanks for all the assistance.
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#10 Old 02-13-2011, 08:35 PM
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Hey, a lot of us tend to think the worst sometimes (you know...with MY freakin' luck!). Glad it worked out for you.

Last edited by VanMoreSon; 02-13-2011 at 08:41 PM.
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#11 Old 02-13-2011, 08:55 PM
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This thread has given me the idea that it is now time to change out my coil pack. Been trying to chase a stumbling problem (most times once or twice within 5 minutes of starting the engine) that I noticed the other day is getting more prevalent (at least 6 times that day).

1977 Chevrolet Impala Sedan, 5.0L, TH200, 2.56:1, 106K miles, 37 Lifetime Warranty Parts.
1989 GMC Sierra Extended Cab 5.7L, 5 Speed, 3.08:1, 327K miles, 0 Lifetime Warranty Parts.
1997 Dodge Ram B2500, gone.


Last edited by 97B2500CCV; 02-14-2011 at 09:35 PM. Reason: Clarifing
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#12 Old 02-14-2011, 09:39 PM
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Just replaced mine this evening. Will be a few days before I know for sure that it has solved mine or not. It never set the MIL lamp, not even for a misfire code.

I dislike random stumbling like that since it make it so hard to trace out the problem.

Primary resistance was at the low end and the secondary resistance was at the high end of the allowable range. Did notice that the secondary resistance would drop as it was cooling down.

1977 Chevrolet Impala Sedan, 5.0L, TH200, 2.56:1, 106K miles, 37 Lifetime Warranty Parts.
1989 GMC Sierra Extended Cab 5.7L, 5 Speed, 3.08:1, 327K miles, 0 Lifetime Warranty Parts.
1997 Dodge Ram B2500, gone.

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#13 Old 02-21-2011, 01:46 PM
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On the catalytic converter thing i just removed mine and run it through the muffler because there was some rattling going on inside. And i thought by removing it it would clear up my annoying stalling dieing problem i have but it hasn't cured that at all but it doesn't run any different without it ether. I live in a state that fortunately doesn't have laws in place for that.
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