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Purchased my first jeep. Overheating cats with p0016 code

Genesiss

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Hello everyone,

I just purchased a lifted 2008 jeep and discovered very quickly it had major issues. My symptoms point to a lot of possibilities. To start, I have a p0016 error code. Replaced cam, crank and temperature sensors.

Tried to clear the code and it came right back.

I noticed very quickly that I had minimal acceleration and zero uphill torque and it got worse every time I would try to use it. On the last trip I limped it to the mechanics shop at 10-20mph and after only 5 miles the catalytic converts were both cherry red and smelled like hot metal.

The engine has 190,000 miles on it. My first thought was that it’s the timing chain and it jumped a tooth and it’s dumping fuel into the cat causing the cherry red hot symptom.

Can I get some opinions? Most likely the chain needs replaced but are the cats the reason for the sluggish behavior or is it the timing chain? Can the timing chain cause fuel to go unburned to the cats? Debating just buying a rebuilt engine then wasting money chasing issues in a high mileage engine.
 

BLACKJKU

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Hello everyone,

I just purchased a lifted 2008 jeep and discovered very quickly it had major issues. My symptoms point to a lot of possibilities. To start, I have a p0016 error code. Replaced cam, crank and temperature sensors.

Tried to clear the code and it came right back.

I noticed very quickly that I had minimal acceleration and zero uphill torque and it got worse every time I would try to use it. On the last trip I limped it to the mechanics shop at 10-20mph and after only 5 miles the catalytic converts were both cherry red and smelled like hot metal.

The engine has 190,000 miles on it. My first thought was that it’s the timing chain and it jumped a tooth and it’s dumping fuel into the cat causing the cherry red hot symptom.

Can I get some opinions? Most likely the chain needs replaced but are the cats the reason for the sluggish behavior or is it the timing chain? Can the timing chain cause fuel to go unburned to the cats? Debating just buying a rebuilt engine then wasting money chasing issues in a high mileage engine.

Cats will plug up and restrict the exhaust flow and also cause the heat.
 
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Genesiss

Genesiss

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Cats will plug up and restrict the exhaust flow and also cause the heat.
My only confusion is the p0016 code. The sluggish behavior also came very quickly. Within 100 miles became undrivable. A bad chain can cause sluggish response and so can a cat but this all happened very quickly. The labor to replace a timing chain and an engine are about the same for me. It’s just the question is it both cat and chain?
 

BLACKJKU

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My only confusion is the p0016 code. The sluggish behavior also came very quickly. Within 100 miles became undrivable. A bad chain can cause sluggish response and so can a cat but this all happened very quickly. The labor to replace a timing chain and an engine are about the same for me. It’s just the question is it both cat and chain?

Probably only way to really know is either pull the cats and see what they look like, or if you take the valve covers off and then turn the crank back and forth you should be able to see how much play there is on the timing chain.
 
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Genesiss

Genesiss

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I would assume though with the p0016 error code at the exact same time the acceleration issue started and with all sensors replaced the timing chain is bad unless the TIPM could cause a false p0016 code?
 

Vman

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I would assume though with the p0016 error code at the exact same time the acceleration issue started and with all sensors replaced the timing chain is bad unless the TIPM could cause a false p0016 code?

A lot of unburnt fuel caused by timing issues could have been what smoked the cats.

On a 2008 3.8 you can check the slack in it by dropping the oil pan and poking it with a screwdriver.

Good opportunity to check for bits laying in the oil pan as well and check the general condition of the engine.
 
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Genesiss

Genesiss

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I ended up ordering a rebuilt engine since the last owner ran it 3 quarts low and it had almost 200,000 miles on it with those cat issues and the jerking, knocking and p0016 code. Allowing Aamco to install it. They discovered the flex plate was trashed in the process and the timing chain was very loose so rebuilt engine, oil pump, flex plate, torque converter, trans cooler then a new water pump and thermostat since they are replacing the engine anyway. The next question I have is since it’s a Dana 30 on the front end Dana 44 on the back with a 3.73 original gear ratio according to the factory sticker on it with the towing package what gear ratio do I need to confirm? I have Ironman 37’s with Dana 30 and 44 I assume based on what i read I can go to 4.88 or 5.13 however most say 4.88 is better and some say 5.38 is needed for that tire size hub that means switching out the Dana 30.

I really just need advice on what I need to do to ensure a dependable vehicle that my wife who really wanted that will not leave her stranded or have a catastrophic break down. I would prefer mpg over power.

Any advice is appreciated.
 
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Vman

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I ended up ordering a rebuilt engine since the last owner ran it 3 quarts low and it had almost 200,000 miles on it with those cat issues and the jerking, knocking and p0016 code. Allowing Aamco to install it. They discovered the flex plate was trashed in the process and the timing chain was very loose so rebuilt engine, oil pump, flex plate, torque converter, trans cooler then a new water pump and thermostat since they are replacing the engine anyway. The next question I have is since it’s a Dana 30 on the front end Dana 44 on the back with a 3.73 original gear ratio according to the factory sticker on it with the towing package what gear ratio do I need to confirm? I have Ironman 37’s with Dana 30 and 44 I assume based on what i read I can go to 4.88 or 5.13 however most say 4.88 is better and some say 5.38 is needed for that tire size hub that means switching out the Dana 30.

I really just need advice on what I need to do to ensure a dependable vehicle that my wife who really wanted that will not leave her stranded or have a catastrophic break down. I would prefer mpg over power.

Any advice is appreciated.
Sorry to hear they had to pull out the rib spreader for you but thanks for the follow up.

Where did you order the replacement engine from if you don't mind me asking?

You've got two issues with 37's on a 3.8: the D30 and the 42RLE 4 speed auto.

You can get 5.38 gears for the D30. No experience on how they'd hold up. That will be the minimum gear ratio for 37's and the max that the D30 can use.

I faced the same issue on my '07 and elected to go with 35's and 5.13's and it turned out to be the right decision. I didn't think the transmission would last long running 37's, especially when the 07-11 doesn't have the transmission coolers that the 12+ models have from the factory. Looks like you got that figured out though as I see it in your list of replacement parts.

That said, I didn't actually put on the 37's, so I have no experience with that. Figured I'd stick with the 35's, upgrade the axles down the line, and would have a set of 5.13 axles I'd have no problem selling to help with the upgrade.

The chart in the link below I can say is 100% accurate for the 3.8 on 35's with 5.13 gears, so is a good place to help figure things out.

5.38's on 37's would put you at about the same RPM's I'm seeing with 35's on 5.13's according to the chart.

 
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Genesiss

Genesiss

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Sorry to hear they had to pull out the rib spreader for you but thanks for the follow up.

Where did you order the replacement engine from if you don't mind me asking?

You've got two issues with 37's on a 3.8: the D30 and the 42RLE 4 speed auto.

You can get 5.38 gears for the D30. No experience on how they'd hold up. That will be the minimum gear ratio for 37's and the max that the D30 can use.

I faced the same issue on my '07 and elected to go with 35's and 5.13's and it turned out to be the right decision. I didn't think the transmission would last long running 37's, especially when the 07-11 doesn't have the transmission coolers that the 12+ models have from the factory. Looks like you got that figured out though as I see it in your list of replacement parts.

That said, I didn't actually put on the 37's, so I have no experience with that. Figured I'd stick with the 35's, upgrade the axles down the line, and would have a set of 5.13 axles I'd have no problem selling to help with the upgrade.

The chart in the link below I can say is 100% accurate for the 3.8 on 35's with 5.13 gears, so is a good place to help figure things out.

5.38's on 37's would put you at about the same RPM's I'm seeing with 35's on 5.13's according to the chart.



I appreciate all the information!! I’ll include the flyer of where I got my engine. I went for the gold standard at the bottom. In retrospect maybe I should have gone for the 3.6 or 4.0. I thought 5.38’s we’re no longer available on Dana 30’s? What are the consequences of running at 4.88 or 5.13?

4D4937DA-BC06-4856-B882-4CE106D3B22A.jpeg
 

Vman

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I appreciate all the information!! I’ll include the flyer of where I got my engine. I went for the gold standard at the bottom. In retrospect maybe I should have gone for the 3.6 or 4.0. I thought 5.38’s we’re no longer available on Dana 30’s? What are the consequences of running at 4.88 or 5.13?

View attachment 120307

Thank you for the info! Looks interesting I've never heard of that company before. Do you know if that one includes a front timing cover or if you have to reuse your old one?

Think I'll contact these guys and see what they say. Always good to have the research done in advance before you need the inevitable.

Mine's getting up there in mileage, though compression and function *knock on wood* is still great for 160k.

Revolution gear looks like it is still available in 5.38 for the D30:


Not sure if you will need a new carrier. I took the opportunity to put in TrueTracs front and rear at the same time, so didn't have to worry about replacing the carriers.

If you check out the previous link you'll see blue/yellow/green/no color charts by tire size/gear ratio/transmission type/3.6 or 3.8. The blue means it would be a good trail only rig for low speed, low RPM so def not daily driver. Yellow means driving on public roads is going to suck. Transmission will be shifting all over the place trying to figure out what it should do especially going up hills. Basically just a feeling that you have no power at all.

Before I regeared it sucked bad. After the regear my transmission is shifting when it should and it is fine on public roads again.
 
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Genesiss

Genesiss

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I got the jeep back today and what aamco advised was the next set of issues.

Oil light is on, this is a new symptom and they replaced my pressure switch even though I just replaced it before bringing it into the shop. Oil levels are good. Aamco believes it’s the cmu giving a false reading. The light did go out for part of the ride home and came back after refueling. I would hope they primed the oil pump, the engine does have what the seller refers to as a larger oil pump, perhaps that’s causing the switch issue? No codes for it.

All four o2 sensors are giving a p0031, p0057, p0051 and p0037. I can only assume the cats overheating before going to the shop until they were bright red and probably a good 2500 degrees damaged the sensors or the cmu needs replaced. All wiring appears to be connected and intact. The mechanic felt all four going out was unlikely.

I also have a p0300 code except again newly rebuilt engine and new plugs so again I’m assuming the cmu.

I have heard the fuse panel is also a culprit and common to catastrophic failure. Since I’m ordering a new cmu any opinions on just replacing that while I’m at it?
 

BLACKJKU

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Sometimes after installing new parts ( engine ) the ECM has to do a relearn and from what I heard you have to drive a certain amount of miles for it to do that.
 
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JeepJeezy

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Sometimes after installing new parts ( engine ) the ECM has to do a relearn and from what I heard you have to drive a certain amount of miles for it to do that.
I've disconnected the positive battery terminal, grounded it on the negative terminal for 30 mins and then reconnected the positive back onto the battery. This method drains all stored memory in the ECU. Now your ECU will relearn everything from the new motor and your driving habits.
 
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Genesiss

Genesiss

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So I’m curious why my red oil low pressure light is on, my first thought is because the oil pump was installed on the rebuilt already and aamco didn’t prime it. The other thought is they used a cheap “Auto extra” oil filter that I believe has a poor bypass valve or none at all. I called them as soon as the light came on about a mile down the road after picking it up and they said they saw the light so after replacing the oil pressure switch they assured me it’s the pcm and it was safe to drive home. That was a 11 mile drive through rush hour at about 45 minutes of which the oil light did turn off once for about a minute and turned back on.

I am going to go to get a Mobil one filter tomorrow. Any opinions on this issue? I’m thinking disconnect the coil pack and spin the starter to prime the oil pump? If the filter has oil then I assume the pump is working? I hope I have no engine damage already by this recommendation to drive it assuming the pcm is messed up giving false readings.
 
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Genesiss

Genesiss

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So I got the oil filter, no change. What I did discover is this model and year doesn’t monitor the oil pressure through the ecm. It appears the red oil light is just a pressure switch. It’s was able to get it to turn off if I grounded it out. I also bled any air pressure trapped by loosening the filter slightly and running the engine briefly to ensure my mechanic didn’t screw up and didn’t prime it.

I have an oil pressure gauge I’ll be connecting today to verify actual pressure.

The bad part is after the engine replacement with the rebuilt and now a rebuilt pcm I no longer have 02 sensor codes but I do have the p0344 now and with the larger tires I have the tpsm light and it’s still in limp mode.

Some say you should only use Mopar parts but others say lately Mopar is no better then aftermarket on sensors.

Part of me thinks the tipm is also trashed and causing some issues.

Has anyone paid for a professional tune to simply eliminate the limp mode feature? It seems like so many non essential issues can cause this mode.
 

BLACKJKU

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Since there is larger tires on it has the speedometer ever been recalibrated? If not that can cause issues with a automatic transmission.
 
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Genesiss

Genesiss

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If you have a Jscan you can set your correct tire size and shut off or set the desired low tire pressure down to 26 ( I think )
The speedometer definitely needs adjustment but the gear ratio is at 3.72 and needs 5.38 for 37 tires on an automatic. The bigger problem is the oil pressure is way over 100psi when I connected a gauge to the oil pressure sending unit port. It maxed out my oil pressure gauge to what I assume is about 130psi as it buried the needle at initial turn over and 1000 rpm.

I didn’t have any signs of damage or leaks or smoke so far.

It’s a new rebuilt engine which could be higher psi initially but not this high. What I am gathering is something is blocked, maybe a return hole on the gasket or a blocked oil passage or bad relief valve.

I sent a rather irate email to aamco since it’s the weekend over sending me home with the jeep and this issue on a rebuilt newly installed engine. Hopefully no damage yet to the seals but now it’s got to be towed back to the garage.
 
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Ok, well I let the engine idle and the oil psi dropped to 28 Psi at 750rpm after 5 minutes. Ran the engine 30 minutes then it stalled out and the p0344 returned. The ignition cylinder is also randomly sticking with the engine stuck cranking. Turned it off manually then tried again. The Ignition only sticks sometimes. It will turn over intermittently. My thought is buy the new oem cam and crank sensors instead of aftermarket. Debating on a new pibm.