Pulled compression and fuel pressure test this evening. All 6 cyl compression around 150-155 and fuel pressure 56 engine off falling to just 49 after 25-30 minutes.

Trying to check the 02 sensors and cats next.

 

• What does this awful smell smell like? Burning oil, rotten eggs/sulfur, coolant, unburned fuel? Or something else?
• What color is the smoke? Is it dark black, blueish-black, or more white like a steam cloud? How quickly does it dissipate?
• Do you ever hear a strange, metallic rattle type of sound coming from under the vehicle, esp. when sitting at an idle?
• Have you ever gotten out of the vehicle noticed an extreme amount of heat emanating from underneath right after one of these episodes?

It sounds like you might have a catalytic converter that the guts have broken loose inside of. If that happens, it can sit inside the converter shell in such a way that it allows sufficient exhaust to flow by it for the vehicle to run fairly normally under light to moderate loads, but cause enough restriction when you load up the engine (like passing a car, or climbing a hill) that the exhaust can't exit the head fast enough due to the backpressure. They can also shift around and randomly restrict the exhaust. When the exhaust gets blocked, the engine can't breathe and it just lays down on you. This will cause random misfires on the bank of the cat that's clogged and often a flashing MIL.

These are often accompanied by a terrible sulfur/rotten eggs smell in the exhaust, and P0300 random misfire code or sometimes P030X codes for specific cylinders. But also there's usually a P042X code for cat efficiency. Although I suppose it's possible that the cartridge in the cat is still doing it's thing despite just sitting loose inside the converter. And often, you will hear a sound similar to a heat shield rattling on the exhaust when the cartridge rattles inside the converter housing. This could also cause the plugs on the affected bank to look like they've been real hot. Because they have. That bank will get scorching hot when the converter is plugged. Like "exhaust manifold and converter glowing red hot" kind of hot. And of course, cylinder 5 would be the cylinder closest to the converter on bank one.

A clogged converter shouldn't cause any smoke or oil consumption, though. Unless it's caused some sort of damage to the engine from extreme overtemps on that cylinder head. You mentioned this may have been developing for the past two years, which is long enough to worry about further damage. I've never seen one take that long to get so bad as to be undriveable. Or, the oil consumption may not be a result of the problem, it could be the cause. You mentioned your PCV, if you haven't changed it it could be stuck open or the spring weakened, allowing oil vapor to constantly be sucked out of the crankcase, through the intake manifold and into the chambers. This will cause sludge and can ruin a catalytic converter over time. A lot of people don't realize how catastrophic a bad PCV valve can become.

Definitely not a diagnosis, but your description certainly reminded me of several vehicle I've seen in the past with clogged cats. They all acted similarly. You could always take it to an exhaust shop and ask them to have a look at it without suggesting a diagnosis to them. One good way to spot a clogged converter is with either an infrared camera or thermometer. The restricted converter will be much hotter than the other. Often, so much hotter that you can feel the difference between them from a couple of feet away when under one on a lift!

Edit to add: When I say an exhaust shop, I am specifically not talking about one of the national rip-off chains like Midas, Meineke, Rapid, etc. Either an independent local exhaust shop or mechanical shop, or a dealership. I've seen those chain "muffler" places try to charge people $800 for a $250 brake job - on a car with brand new brakes!

 

you did compression and fuel pressure, they appear to be good, you are tracking down that oil leak, let us know Yes the valve cover is the first thought.

Step 1
You said the CEL was flashing and is ON, any chance you have a scanner check for codes,

Looking at the freeze frame and then a look at live data. I like to see - ECT, TPS, MAP, fuel trims long and short and I like just the pre cat o2 sensor voltages.BUT both would help with checking the CAT.

It was suggested the CAT may be your problem- looking at live data we MAY be able to check the concerns out 3 thoughts on that 1) it would set a code, 2) we could look at MAP and check for restriction 3) a look at the pre and post cat o2 readings would help with checking that cat.

Check The cooling system, remove the radiator cap and check, don't just look at coolant overflow bottle.

ALSO the jeep is STOCK - no BS- programmers, chips, miracle air filters, modifications, add on ?

SIMPLE take away from the ideas - check for codes SCAN, remove radiator cap to check coolant level.

 

Thanks guys. I have a cheap obd2 scanner from amazon I was able to pull some live data off. There were 3 or 4 codes other than the p0300 when we got the jeep home that day but I had cleared them after writing them down and lost the paper since. Figured I had driven it under conditions it wouldn't have seen trying to make it home that day so the codes at the time would be best cleared and just see what popped back up afterwards. One was maybe a p0420 and one was maybe a p013x (p0131 from my memory). Dont recall about the others.

The air filter, air intake, and maf(mass?) Were quite oily - pulled the PCV out and the spring/stopper looks broken it's very loose and just falls open-shut if tipped upside down. If its bad and causing excess blow by into the intake, ruining the cats over time?

Haven't found the infrared thermometer I have but by hand after a 20 min idle the cats both feel hotter on the engine side than on the back side. No noise heard rattling in them though.

Posting live data in a minute. Wondering about the cell phone app obd2 readers something better to capture live data and post it here in a readable file ?

 

Live data written down after watching each data point for a minute or two. Monitored a few minutes after startup to about 20 minutes running. Cleared codes and monitors a few days ago have done 6 warm ups since but no driving other than up and down our drive way. If that makes any of these reading change just wanted to point it out.

ETC 27c after 5min idle to 101c after 20min idle
Shrtft1 % bounce from 2.3 to -7.3 mostly staying 0.0 to -6.0
Longft1 % staying -4.7
Shrtft2 % bounce 3.8 to -7.0 mostly 0.8 to -4.7
Longft2 % 0.0
Map (kpa) 36-37 @ idle 5min after startup and 34-35 about 20 minutes later (will spike quick to about 52 and drop to 30 if rev and hold to 2k rpm)
Idle rpms about 600
IAT 20c after 5min idle to 38c after 20min Idle
Sparkadv 9 to 12 degrees
TP% 13.3
02B1S1 fast bounce from .005 to 0.84* (0.005,0.135,0.450,0.840) random up back down and repeat
Shrtftb1s1 % 3.9 to -4.7
02b1s2* 0.155 to 0.920
02b2s1 0.055 to 0.820
Shrtftb2s1 % 0.8 to -3.9
02b2s2 0.820*stuck (0.78 to 0.90 if rev)
Evap pct* % slow bounce 31.4 to 32.5
Fli % 33.7
Catemp11 380c after 20 min idle
Catemp21 380c after 20 min idle

Aat 29c after 5 min idle to 37c after 20 min idle


I'll look for a better way to capture and post the live data and I still need to grab a freeze frame which I forgot about today. Stock Jeep original on everything. So glad to have help thanks much guys

 

The P0420 code is expected and fairly telling, as I mentioned before it would be right in line with a burned up converter on the suspect bank. If you can find that paper, it might have other informative codes. The problem with clearing them is that many monitors won't complete and set a code until one or more full drive cycles under specific conditions, which of course you cannot complete now because the vehicle is virtually undriveable.

I'd asked about the characteristics of both the smell and smoke you had mentioned, that info might still be informative. Also, I forgot to mention in my first response that your description of having to "feather" the throttle to get the vehicle to move exactly mirrors my experience with vehicles having plugged up converters.

PCV valves usually should rattle when shaken, when they don't rattle it's usually a bad sign. However, just because one rattles doesn't mean it's working properly. It's hard to tell from a written description if it looks normal or broken, but if you've never replaced it it's no doubt due for a new one. They are considered routine maintenance type items and the factory service schedule is to inspect and replace if necessary every 30k miles. I wouldn't replace it until you get the real problem sorted out, though. The current problem might just destroy a new one, as I explain below.

If I'm reading and understanding the PID values you posted correctly, it looks like the upstream O2 sensors are switching normally, they should constantly switch low-high-low-high. This is because the converters need oxygen to do their thing, so the PCM switches the air/fuel mixture from slightly lean to provide unburned oxygen to the cat, then back to slightly rich, etc. When the cats are working properly, this unburned oxygen will be trapped by the catalytic material in the converter, then used to oxidize the polluting combustion byproducts into less harmful emissions. So, when things are working properly, the downstream O2 sensors don't see that oxygen before it's combined with other combustion products. Therefore, the downstream O2 sensors should show a pretty stable reading indicating low O2 levels in the downstream exhaust. Of course, more will get by when accelerating hard or suddenly getting off the throttle because the catalytic reaction can only work so fast. But sitting at idle like it was when you were watching the data, you should see the upstream sensor voltages oscillating up and down and the downstream sensors remaining fairly stable.

It appears from your description that the bank 2 downstream sensor voltage is stable, as it should be if the converter is capturing the oxygen leaving the cylinders. But the bank 1 sensor 2 (downstream) reading is almost mirroring the bank 1 sensor 1 (upstream) voltage. This is an indication that the catalytic material in the converter between them is no longer working as it should. After all, if there were no catalytic converter between the upstream and downstream O2 sensors, you would expect the oxygen reading at both of them to be identical, right? And that's almost what you're seeing on bank 1.

Fuel trims don't look out of the ordinary (but then again, you're just sitting at idle), but the PCM is leaning out bank one a little, probably due to combustion efficiency problems even with your new plugs. Your bank one cylinders may be fouled up, and if that bank 1 cat is partially melted inside, that bank is no doubt not breathing well.

I'm not a mechanic, and I'm not the one who'll be out a substantial amount of money for an unnecessary new converter if my speculation is wrong. So I would highly recommend not rushing off to buy a new one until you get more input from either Jtec or a local shop. If I absolutely had to make a speculation on what's going on: As your spark plugs wore out and the gaps got larger and larger, the spark got weaker. Therefore, the engine was not burning all of the fuel being injected. That raw fuel exited the cylinders and wound up in the converters, where it did burn (auto-ignition temp around 536°f, catalysts run over 1,000°f.) This probably would have resulted in black smoke from the tailpipe, especially when gunning the engine. This fuel burning up in the converter caused the converter to get extremely hot, and the honeycomb catalytic material inside of it began to melt. As the catalyst began melting and getting less and less effective, this was the source of the smell you mentioned. Eventually, the honeycomb melted enough that it began restrict the flow of exhaust through it, causing a lot of backpressure in the manifold and head due to not all of the exhaust gasses being able to exit the engine. This backpressure created a lot of blowby past the rings in the cylinders on bank 1, pressurizing the crankcase with exhaust gasses that had nowhere else to go. The pressurized exhaust gasses escaped the crankcase both through the PCV valve into the intake, and back out the fresh air tube that usually supplies filtered air into the crankcase for the PCV system to suck through into the intake. This would explain your oily air filter and intake. If this is true, I'm amazed you're still getting equal compression across all six cylinders. Also amazed if you don't have oil leaks at the main seals, oil pan, and/or valve covers from the pressure where there isn't meant to be any.

My suggestion from earlier still stands: have a shop (preferably dedicated exhaust shop) evaluate it, because a converter is an expensive roll of the dice and it's difficult to be certain that one is bad without a gas analyzer, unless the honeycomb inside has broken up and is rattling. In your case, it sounds like it hasn't broken up, just melted into a blob. If you guess and DIY it, and are right, you'll save a couple hundred in labor. If you guess and are wrong, you'll be out at least several hundred for a converter and still have an undriveable vehicle.

 

Thanks, your input is much appreciated Rick! I think you're right with your suspicions on the one cat. Next time I have to work on it I may try removing the upstream 02 from that bank and see if the extra airflow out the bung will get the jeep driving without a misfire or one that is as easy occuring. Read that's one way to DIY cat test so worth a shot? Perhaps I can get a camea in there and see broken or melted combs. Will see what we have for exhaust shops locally but kind of last resort with the money it'll cost.

Off from memory about the smoke and smell, it was usually a dark gray/blue. Comes out mildly thick and travels a good ways before dissipating out. Smell was burnt oil and fumes but had sulfurish whiffs come and go if I do remember.

And about the upstream downstream 02 voltages, I think you are right there too. One bank was looking the same between the up and down bounces nearly identical, swinging low high low high the other bank held steady and high (.78 to .82) mostly without moving at all unless I revved the throttle. I think then it would drop a little and then raise right back up and stay again.

Will update more in a day or two.

 

From looking at pictures of converters for 3.7s online, it looks like the upstream O2 sensor on bank one is a long ways above the converter. I doubt you could get a camera from there all the way down into the converter. You could try going in from the downstream bore, but that would be looking at the wrong end of the honeycomb, and it might look normal (or maybe not). If you can get to it, leaving the upstream sensor out might give you an idea of whether or not the cat is the reason the engine won't rev above idle, just be really cautious of where that hole points. The gas coming out of it is going to be scorching! I wouldn't try driving it like that, in fact I wouldn't run it long at all, just long enough to see if it will rev better with the sensor out than with it in. If you do manage to find your infrared thermometer, there should be a pretty marked difference in temps between the pipe just ahead of the converter and after it if it's plugged up.

Here are a few articles about converters, one has a picture of a healthy honeycomb, another has a picture of a partially melted one for reference and the third just interesting general info:

https://www.knowyourparts.com/technical-resources/engine/catalytic-converter-basics/
https://www.knowyourparts.com/techn...s.com/technical-resources/engine/new-catalytic-converter-diagnostic-strategies/
https://www.knowyourparts.com/technical-resources/engine/catalytic-converter-efficiency-meets-eye/

Persistant blue-gray smoke is usually oil burning. If that problem long predated the issues with the cat, maybe some of the oil problem did come before the cat problem, though I suspect a plugged cat is the reason you've got oil all the way back to your air filter. The question then becomes where was that oil coming from? A bad PCV valve wouldn't cause enough oil consumption to be smoking like that. If you wind up replacing the cat, you'll need to figure that oil consumption out immediately, if not before doing the cats. If it's still burning oil at the rate you said it was before, you'll just wind up having to replace the converters again soon. The fact the issues all seem to be confined to one bank makes me wonder if there's something going on physically on bank one, letting oil get into one or more of those cylinders. A valve seal maybe? Maybe Jtec will have some opinion on a likely cause.

Basically, converters almost never go bad on their own. It's something going on upstream that winds up taking them out, like incomplete combustion, oil consumption, coolant leaking into cylinders or intake, etc. If you don't figure out and address whatever took this cat out, it's just going to take the next one out, too. Once again, assuming it is the cat. I still recommend getting a diagnosis from someone actually looking at the vehicle before throwing a $500 set of converters at it. Good luck, and please let us know what eventually comes about in case someone else has the same problem in the future and stumbles upon the thread. It's so aggravating to google some problem you're having, and find a thread about the exact same problem, but then it just ends with no resolution or idea of whether or not they ever figured it out!

 

Had time for a quick cat test tonight after finding the infrared thermometer. Had the jeep warm up for 15-20 minutes then sat it in and held rpms to about 1800 for a minute or two. Left it running and got under and tested on the exhaust pipe about 2 inches before and after both cats as any closer and the thermometer would max its 500f reading.

Bank one driver's side inlet temp about 475f and outlet temp about 435f.
Bank two passenger side inlet temp also about 475f but outlet 495f to maxing over the 500 reading.

 

The fact that bank 1 is substantially cooler downstream of the converter than upstream further strengthens my suspicions about that cat being plugged up. If you were to try to drive it a short distance, so that the engine was sputtering a little due to inability to breathe, I'd wager you'd see a much greater difference between inlet and outlet temps on bank 1. I can't think of anything else for you to do on your own to confirm it, short of pulling the upstream sensor (if it isn't pointing right at something the scorching exhaust coming out will ruin or ignite) and seeing if the engine can breathe better with a way for the exhaust to exit bank 1 rather than through the converter. Or you could drop the Y-pipe and start it briefly and see if the inability to pull itself goes away.

I still think you ought to get a professional opinion before crossing your fingers and throwing a fairly expensive part at it.

If you can weld or know someone who can (possibly a local exhaust shop), you could always cut the old cat out and weld in one of those universal converters and save several hundred bucks. It looks like you can get the Magnaflow Federal (the CARB version if more, of course) universal that fits it for about $125 on Amazon. At least that would solve your exhaust restriction, but I'll almost guarantee you'll have a P0420 code for cat efficiency soon if not immediately. Those universals usually barely have enough catalyst material in them to pass muster when brand new, a name brand like Magnaflow might not be as bad. That would get it driveable again, possibly with a check engine light. If it set a cat efficiency code, you couldn't pass an emissions inspection if your state does those. Otherwise, there are direct-fit (complete Y-pipe) "brand-you've-never-heard-of" options available on eBay and Amazon from $300-$600. These are also lower quality with lower quantities of precious metals in them than OEM converters, so there's a decent chance you'll wind up with cat efficiency codes, but at least they'll let the engine breathe and don't require welding/fitting like a universal. I imagine the OEM Y-pipe is somewhere well north of $1,000.

Once you get it running again, you'll need to figure out right away if it's still consuming oil and if so how, and get it fixed, or you'll just be right back in the same situation again once the new converter burns up. Hopefully, the converter burned up due to the worn-out plugs you already replaced, and all of the oil consumption problems were due to the clogged converter and not an internal engine problem. The oil in the plug well does suggest your valve cover is leaking.

 

I imagine the OEM Y-pipe is somewhere well north of $1,000.

Very well north of $1,000. US list price was $2500 as of last year.

 

Appreciate that info! Definitely rather be headed towards the path to a magnaflow universal vs the 1.2k or more direct fit pieces. I'll need to think about the next steps before jumping in though. Will attempt to look at it more myself before passing it to a shop or pulling the trigger on a cat and weld job.