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Unread 11-03-2013, 04:07 PM   #1
BrugsBunny
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So my buddy from work (I'm a mechanic) just got done with replacing a cat on a 2004 WJ, I6 4.0, and now it's having some SERIOUS issues. It had come in with a misfire originally, as well as needing a new cat and O2 sensors in both banks, and now that those have been replaced, the misfire is even worse, there is white smoke pouring out of the tail pipe, and the cat is glowing red within a very short period of time after cranking up. So he needs to know if it's a head, or something else, or if anybody here has any clue of what it might be.

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Unread 11-03-2013, 04:19 PM   #2
MuddyWJ
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The only way the cat turns red is if there is a clog in the system. If you have a infrared temp sensor let the vehicle warm up then hit the laser before cat and after. Shouldn't be a huge temp difference.
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Unread 11-03-2013, 04:32 PM   #3
nickblack
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I had multiple misfires after putting in an aftermarket cat. I was running those E3 spark plugs at the time, which were a mistake in the first place. It turned out to be the plugs and after I put in the OEM plugs, everything was fine. I don't know if it was a coincidence, but the plugs gave me no trouble when I had the OEM cat in. What kind of plugs are you running?
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Unread 11-03-2013, 04:53 PM   #4
PA55
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Maybe the cat is pulling air in at the front joint or the O2 sensor, also check the sensor wiring.

Jim
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Unread 11-03-2013, 05:50 PM   #5
TJSWJ
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You say "A" cat. This vehicle has 3 converters. Which one did he replace, and why? Did it have an efficiency code?

White smoke usually indicates a blown head gasket. To ad to that, coolant kills converters and o2 sensors rather quickly. Was the coolant level low? What do the spark plugs look like?

With white smoke, a miss fire, a bad cat, and bad o2' s, I'd lean towards a head gasket failure. Time to check the coolant level, and do a chemical test on the cooling system. If it passes the chemical test, the proceed with a compression test followed by a cylinder leak down test.
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Unread 11-03-2013, 05:52 PM   #6
Darnice
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Quote:
Originally Posted by MuddyWJ View Post
The only way the cat turns red is if there is a clog in the system. If you have a infrared temp sensor let the vehicle warm up then hit the laser before cat and after. Shouldn't be a huge temp difference.
Actually, no, if it has a bad missfire, its dumping raw fuel into the exhaust and it burning in the cat con. Problem is if you run with a miss fire bad enough, you can melt the inside of the cat con and ruin it.

Fix the missfire, hopefull the cats still ok. White smoke is usually a blown head gasket of cracked head, coolant burns white, and could be causing your missfire. Pull the spark plugs and see if one looks different.
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Unread 11-03-2013, 10:11 PM   #7
BrugsBunny
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Quote:
Originally Posted by nickblack
I had multiple misfires after putting in an aftermarket cat. I was running those E3 spark plugs at the time, which were a mistake in the first place. It turned out to be the plugs and after I put in the OEM plugs, everything was fine. I don't know if it was a coincidence, but the plugs gave me no trouble when I had the OEM cat in. What kind of plugs are you running?
I have no idea what plugs are in it, it's not his or my vehicle, it was I the shop today...but we didn't do anything with the plugs, the OBD said bad cat and bad O2 sensors, but the problem with the glowing cat didn't come about til he changed all of that. So in that case next step is to run a compression test you think? Maybe a bad head?
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Unread 11-03-2013, 10:15 PM   #8
BrugsBunny
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Quote:
Originally Posted by TJSWJ
You say "A" cat. This vehicle has 3 converters. Which one did he replace, and why? Did it have an efficiency code? White smoke usually indicates a blown head gasket. To ad to that, coolant kills converters and o2 sensors rather quickly. Was the coolant level low? What do the spark plugs look like? With white smoke, a miss fire, a bad cat, and bad o2' s, I'd lean towards a head gasket failure. Time to check the coolant level, and do a chemical test on the cooling system. If it passes the chemical test, the proceed with a compression test followed by a cylinder leak down test.
he swapped out the y pipe so it would've been all of the cats and both the sensors that connect to the pipe...so I'll take this to him tomorrow when I go in and we'll look into it, and I think at this point a compression test is in the forecast...I'll have to get more info from him, the only info I got was via phone call this afternoon (I had the day off) but this should be helpful in taking the next step.
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Unread 11-04-2013, 11:29 AM   #9
Jeeples
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I think you need to slow down a bit with the diagnosis before jumping to a compression test. I think you jumped the gun with replacing the O2 sensors and possibly the y-pipe/cats.

You need to start by diagnosing the misfire first, I am willing to bet if you fix the cause of the misfire, your other symptoms will go away. Like was mentioned earlier, hot cats are either caused by being plugged or by raw fuel burning in the cat itself. Since the cats are new, its probably safe to say they're not clogged. So now that we've ruled out a clogged cat, we know the other cause of a glowing cat is raw fuel, we also have a misfire code as well. Misfires are either caused by a fuel issue (leaky or non-functioning injector), a spark issue (bad coil or plug) or a mechanical problem (bent valve, dropped seat etc.).

What cylinders are getting the misfire codes? Start by checking plugs in those cylinders. If the plugs are wet and smell like fuel, ensure the coil packs are working. If you're getting spark, test for leaky injectors by pulling the rail and turning the ignition to 'On'. This will pressurize the fuel rail, watch for any injectors that are stuck open or dripping. This can take awhile, so you'll want to watch them for at least 20-30 minutes while the pressure bleeds off the fuel rail.

If the ignition and fuel systems are working properly, then go ahead and do a compression test. If you have a scope/camera you can look inside the affected cylinders for piston or valve damage as well.

Good Luck.
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Unread 11-05-2013, 06:50 AM   #10
nickblack
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Jeeples advice is by far the best you have gotten. I would follow along with his line of thinking.
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Unread 11-05-2013, 07:03 AM   #11
BrugsBunny
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Quote:
Originally Posted by Jeeples
I think you need to slow down a bit with the diagnosis before jumping to a compression test. I think you jumped the gun with replacing the O2 sensors and possibly the y-pipe/cats. You need to start by diagnosing the misfire first, I am willing to bet if you fix the cause of the misfire, your other symptoms will go away. Like was mentioned earlier, hot cats are either caused by being plugged or by raw fuel burning in the cat itself. Since the cats are new, its probably safe to say they're not clogged. So now that we've ruled out a clogged cat, we know the other cause of a glowing cat is raw fuel, we also have a misfire code as well. Misfires are either caused by a fuel issue (leaky or non-functioning injector), a spark issue (bad coil or plug) or a mechanical problem (bent valve, dropped seat etc.). What cylinders are getting the misfire codes? Start by checking plugs in those cylinders. If the plugs are wet and smell like fuel, ensure the coil packs are working. If you're getting spark, test for leaky injectors by pulling the rail and turning the ignition to 'On'. This will pressurize the fuel rail, watch for any injectors that are stuck open or dripping. This can take awhile, so you'll want to watch them for at least 20-30 minutes while the pressure bleeds off the fuel rail. If the ignition and fuel systems are working properly, then go ahead and do a compression test. If you have a scope/camera you can look inside the affected cylinders for piston or valve damage as well. Good Luck.
It's misfiring on 2, 3, and 6... The owner actually replaced the spark plugs rather recently so it's not likely to be a plug issue. Given your post out next step is looking into the injector to see why it's dumping fuel...but we're almost certain that there's a cracked cylinder given that there's coolant being dumped into the exhaust...
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Unread 11-05-2013, 07:55 AM   #12
doityourselfMM
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It's early and I'm just thinking out loud, but the fact that the owner just replaced the plugs could be a cause for concern. Don't get burned by assuming the plugs are OK. When I troubleshoot, I don't take anything for granted. I always want to see for myself.

As to the coolant, is the overflow reservoir low? When you remove the oil filler cap, are you seeing any 'milky' looking oil inside the valve cover?

Best of luck!
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Unread 11-05-2013, 09:54 AM   #13
Jeeples
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Quote:
Originally Posted by BrugsBunny View Post
It's misfiring on 2, 3, and 6... The owner actually replaced the spark plugs rather recently so it's not likely to be a plug issue. Given your post out next step is looking into the injector to see why it's dumping fuel...but we're almost certain that there's a cracked cylinder given that there's coolant being dumped into the exhaust...
Again, don't jump ahead of yourself. Start with the basics first and don't assume that new(er) parts are functioning properly.

Also, why do you think coolant is being dumped into the exhaust? Is the engine going through coolant? Again, don't assume that white smoke is coolant, since burning coolant will look more like steam, or when an engine is warming up on a cold morning. Actual thick white smoke (think like just after a Seafoam or Mopar CCC treatment) can be an indicator of too much fuel and/or unburned fuel.

The 2004 4.0's aren't know for cracking cylinder heads like the earlier models are.

Quote:
Originally Posted by doityourselfMM View Post
It's early and I'm just thinking out loud, but the fact that the owner just replaced the plugs could be a cause for concern. Don't get burned by assuming the plugs are OK. When I troubleshoot, I don't take anything for granted. I always want to see for myself.
Yep. In fact the very first plug change I ever did on my wife's WJ (when we were dating) I got a misfire CEL and a stumble about 1 week after putting in new Champion Truck Plugs on cylinder 8. I ran through all the diagnostics for a misfire, but assumed the plug was good. After dropping it off at a local shop to have them look at it, the first thing they did was replace the plug with a new one and the problem went away.
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Unread 11-05-2013, 12:23 PM   #14
1hotrod
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The first CAT didn't glow because it was bad, the first CAT was probably spent i.e., there was nothing there to re-burn the fuel in the exhaust. Now that you have a new CAT it doing it's job. As far as the white smoke, most likely a head gasket. One or two of the plugs where the gasket failed will be absolutely clean no carbon nothing your are basically steam cleaning those plug(s). As far as the misfire goes, a bad head gasket will give you a misfire. Is your overflow tank bubbling by any chance??
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Unread 11-08-2013, 10:47 AM   #15
Jeeples
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Any update on this?
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