P0431 + Oil Pan/Pressure Guage

[BlackNBlue-ISH]

I've got two separate issues (concerning the jeep anyways).

First, the oil pressure gauge. When driving down the street at any speed, the gauge reads correctly. But, when I slow to idle, the gauge drops down to zero and the "CHECK GAUGES" light illuminates. If I give it a little throttle, up to about 1k rpm, the gauge climbs back to normal. It might be helpful to know that my oil pan has taken a pretty good hit in the past and is caved in pretty good. Could that be the cause of the oil pressure? Or could it be something else? Anyone know how easy it is to replace the oil pan? I've heard that with an 04-06 4.0L, you have to be careful with the rear main seal, but is it something that a normal guy like myself can do?

Second, I've got an engine code. P0431 "Warm Up Catalyst Efficiency Below Threshold (Bank 2)". I took the jeep to a non-jeep general mechanic and he said the code points to the 5th O2 sensor after the third cat. He said the O2 sensors are working properly and that the cats are bad. Has anyone had experience with 04-06 TJs with this code (exhausts are different on TJ's previous to that I believe)?

If the cats are in fact gone and need replacing, I've found a site that carries a number of options. Cost is a factor, but I also don't want to buy crap cats and have them not be 100% compatible and crap out after a few years. The options are:
http://www.autopartswarehouse.com/sku/J ... ?loc=Front - $414.71
http://www.autopartswarehouse.com/sku/J ... ?loc=Front - $397.34
http://www.autopartswarehouse.com/sku/J ... ?loc=Front - $373.06
http://www.autopartswarehouse.com/sku/J ... ?loc=Front - $334.87

Anyone have experience with that site/products?

Ultimately, I'd probably try to tackle both the oil pan and cats at the same time given the cats have to come off to replace the oil pan, and if I have to replace the cats, I might as well tackle the oil pan. I'm just cheap.

Thanks in advance for the help!

[del_TJ]

I had the same issue with the low oil pressure reading at idle when the jeep was nice and warm, and it was due to an aftermarket pressure sensor. One remedy is to try to install an OEM sensor. You can also hook up a mechanical gauge to check the oil pressure but I've never done it. I ended up upgrading to a high flow Melling oil pump and now it's fine It can be messy to remove the oil pan and you will have to unbolt or remove the front part of your exhaust to have enough room. It's doable with some basic tools, and it helps to have a torque wrench, jackstands and something to cut off rusted exhaust bolts if necessary.

[del_TJ]

And, here's a rear main seal write-up that I've used before. It'll give you an idea of what's involved in removing and installing the oil pan. You can see from the pics that the rear main seal is inside of the rear bearing cap, so there's no way to harm it by only removing the pan.

http://www.dailydriventj.com/forum/viewtopic.php?t=811

[BlackNBlue-ISH]

That write up definitely makes it look easy to remove and replace the pan. Though, it looked like the motor was out of an older TJ and mine being an 05, i've seen that it takes special care around the rear main seal to make sure the pan seals properly. Any thoughts on that?

[Frank]

Make sure you put silicone (black) in all places where gaskets end . I would use some spray adhesive to hold the gasket in place on the pan and make sure all surfaces are clean of any oil. Use a scrapper and then some brake cleaner . Do not over tighten the bolts. If you dont have a torque wrench , borrow one. There is probably a bolt sequence to the oil pan bolts, follow it. Usually from the middle to the outer ends. FjR68

[BlackNBlue-ISH]

Thanks frank!

[DDewar53]

I had a 1990 YJ with the same oil pressure symptoms. I stopped using cheap NAPA brand oil and started using Valvoline (straight 30 weight, not multi-vis) and that took care of it.

[BlackNBlue-ISH]

I had a 1990 YJ with the same oil pressure symptoms. I stopped using cheap NAPA brand oil and started using Valvoline (straight 30 weight, not multi-vis) and that took care of it.

I typically use a penzoil/valvoline or similar, synthetic from pep-boys and a non-fram filter.

I've taken delivery of an oil pan, and the cats are due to arrive tomorrow. Once the pan filter comes in, hopefully I can pull off the cats, pan, and replace them all without issue.

[DDewar53]

I had a 1990 YJ with the same oil pressure symptoms. I stopped using cheap NAPA brand oil and started using Valvoline (straight 30 weight, not multi-vis) and that took care of it.

I typically use a penzoil/valvoline or similar, synthetic from pep-boys and a non-fram filter.

I've taken delivery of an oil pan, and the cats are due to arrive tomorrow. Once the pan filter comes in, hopefully I can pull off the cats, pan, and replace them all without issue.

I've found that while synthetics tend to provide much better protection, they do run lower pressures than dino oils. Good deal on the non-fram filter, though - I don't like them either. It's funny how products like that can get to be #1 sellers while scoring so poorly in opinion surveys. Other examples like this are Folger's coffee and Corona beer - both #1 sellers in their areas, both consistently score at the bottom on opinion surveys. Weird.

[Carl McFly]

First, the oil pressure gauge. When driving down the street at any speed, the gauge reads correctly. But, when I slow to idle, the gauge drops down to zero and the "CHECK GAUGES" light illuminates

Second, I've got an engine code. P0431 "Warm Up Catalyst Efficiency Below Threshold (Bank 2)"

Ish - I had the same oil pressure problem on my XJ. Exact same issue. Swapped the sending unit, problem fixed. Might have cost $15 and 10 minutes

P0431 - I thought that was the code I threw a few months ago? But like you say, older TJ's have different exhausts. Mine was due to one of the four O2 sensors on my split exhaust manifolds. New O2 sensor = happy Heep. Hope it's just that, and not a cat