rusted exhaust bolt removal?

[Jimmy9190]

Originally Posted By: JamesBond
What is wrong with the catalytic converter? Why do you need to replace it? if its just a check engine light, you could get away with just changing the sensor or something.

I like to spray with PB blaster or something then put on a couple drops of motor oil, then repeat often for as long as you have. If you are still driving the car, whatever you spray on will kind of burn up/burn off so its best if you can let the car sit for a day or two.


Truck threw a P0432 code while driving in to work one day last week. Code means the bank 2 cat is half way below threshold, which is OBD2-speak for the PCM thinks the cat is not working right. Truck has 162K on it now, it could be a bad cat but there are also a few other causes for the code. I need to be sure what is wrong before I go fooling around with the exhaust bolts.

 

[MarkM66]

Use an O2 spacer. Clear code with a reader. Then see if it passes inspection. Could save a bunch of time and money.

 

[eljefino]

OP doesn't even have inspection to pass.

I bet his truck is in the best shape of anyone in his zip code.

 

[Jimmy9190]

Not the best shape, but thanks anyway..I did not buy a thermometer tonight. Instead I filled up with gas and came on home. I checked my truck's performance and it is running fine. I passed a semi going up hill in 5th gear with the AC on and still had throttle left. Throttle response and speed on straight roads is fine, same as it always has been. Not the fastest truck on the block but not too slow either. I read that when the cat fails the vehicle will not speed up when you hit the gas. That is not the case with my Dakota.

Fuelly.com shows an exact 1 MPG drop since my last two fuel fills. I don't think that is too far out of the ordinary, it dropped almost 2 MPG back in the beginning of September. I may have taken a few more short trips on this last tank.

I read online the PCM measures cat efficiency by taking readings from the upstream and downstream O2's. I am just wondering whether my upstream O2 is bad, and causing the P0432 efficiency code. I just do not have the other classic symptoms of cat failure. The exhaust does not have a rotten egg smell or raw fuel smell either.

As always, any help is much appreciated on this.

 

[eljefino]

When the cat's clogged, you'll know it, it'll choke. This happens if the guts break apart and then spin and jam up the outlet like little "death star" golf ball things that aren't lined up so the honeycomb passes air anymore.

But if it's "worn out" eg the platinum is covered with junk so it can't react anymore, it'll pass smoke just fine. Have read of some using laundry detergent to clean them up...

 

[KB2008X]

I wouldn't put much stock in the "classic" bad cat symptoms. I don't think I've seen any two fail with the exact same symptoms. And if you don't have to pass an emissions test of any kind and the truck runs fine, don't sweat it. In a case like this, sometimes the best course of action is to just wait and see.

If the CEL being on bothers you try the O2 spacer that MarkM66 rightly suggested, and/or check the cat's before and after temps so you'll have some facts to work with instead of frettin' & guessin'.

 

[Jimmy9190]

Yep, I agree. I am going to pick up the infrared thermometer and check the cat temps tonight after work, it's on sale for $26.99 and I hope they let me use a 25% coupon on top of the sale price. I have watched a few videos on testing the cat temps and I hope it will tell me more about what is going on. We don't have emissions testing here but I still want to figure this out and fix the problem. I need the CEL to be off and working like normal so it can alert me if any other problems come up in the future.

 

[1 FMF]

if the truck has never had any codes or any real problems during its life and all you are getting now is p0432, with 160k miles the code is probably correct and you have a used up cat. if the engine burns oil at all or if you've fuel additives in the past that will contribute to shortening the life of the cat. the average life of a cat is said to be around 100k miles, the catalysts eventually wear out or get used up, and they are warrantied to 80k i think under federal emissions laws.

 

[javacontour]

When I put a Borla exhaust on my SVT Contour, I simply took it to an exhaust shop and paid them $20 to have them replace the fasteners at the Cat.

I drove the 1/2 mile home and then dropped the factory exhaust and installed the Borla.

It might be worth it to have a shop simply replace the fasteners before you tackle the job.


Originally Posted By: wtd
After the last few failed attempts on working on rusted exhaust bolts and O2 sensors, I just take it to an exhaust shop and let them do it. The aggrevation is just not worth it to me anymore.

Heat is your friend. Just make sure whatever you have will get the metal hot enough. Good luck.

Wayne

 

[Mr_Incredible]

Sawzall wrench or cut-off wheel wrench.

 

[Jimmy9190]

I checked with the only exhaust shop in town yesterday, he left me a voice mail today saying he had researched it and found it is OK to use a universal cat for the replacement. Said the cat would cost about $100.00 but he needs to see the truck first before quoting a price on labor. I am not so sure about the universal cat. And I do believe more tests need to be done before I replace the cats. I am going to pick up an infrared thermometer and a better scan tool that will read O2 voltages before I decide what to do on this. I want to be sure of what is causing the code before buying any more new parts.

 

[JamesBond]

How long has the light been on? How often/far have you driven the car with the light on? Does it go on and off?

I believe the code you have comes up when a downstream o2 sensor reads a value that differs from normal as compared to the upstream o2 sensor. Meaning that your catalytic converter could be bad but also that the downstream sensor could be bad.

I would wait and see if the light goes away on its own before spending any money. Maybe get the engine/exhaust good and hot, with a highway drive in a lower gear, or give it a dose of Techron/Regane.

 

[yonyon]

Originally Posted By: JamesBond
I believe the code you have comes up when a downstream o2 sensor reads a value that differs from normal as compared to the upstream o2 sensor. Meaning that your catalytic converter could be bad but also that the downstream sensor could be bad.


No, this is wrong. He's just replaced it so that already makes it a bit unlikely. Also, it is exteremely rare for a downstream O2 sensor to fail in such a way as to set a cat code. I have seen a few upstream O2 sensors cause a cat code and even that's becoming less common in recent years but never have I seen a downstream do that. It just doesn't work that way.

 

[Jimmy9190]

Well I picked up a nice code reader at HF tonight, it reads live data and is actually a very nice tool with a lot of useful features. I also got an infrared thermometer, it is also a nice tool and will probably come in handy again some time.

I checked the temperature at the right bank cat, at a 700 RPM idle, the inlet temp to the cat was 350, outlet was 540. With Mrs. Jimmy in the driver's seat holding the throttle at 2000 RPM, the inlet temp was still 350 and the outlet temp changed to 560.

At a 700 RPM idle the left upstream O2 read .012 to .8 volts, changing fast.

The left downstream O2 read .4 to .7 and was pretty steady and slower in its switching.

The right bank upstream O2 at idle read about the same as the left, it went from .018 to .82 volts and switched fast.

The right bank downstream O2 had a big difference in voltage from the left bank downstream. It was switching from .16 to .76 of a volt. I have no idea if the lower threshold of voltage on the right downstream makes any difference.

From reading the live O2 data at a steady 2000 RPM the right bank upstream O2 switches rapidly from .3 to .8 volts. The left bank upstream sensor is switching rapidly from about .016 to .8 volts. Neither one went over .8 of a volt during testing.

The downstream O2 on the left bank read anywhere from .5 to .8 at 2000 RPM.

The downstream right bank sensor was reading from .16 to .74 of a volt at the same 2000 RPM.

It looked to me as if the right bank downstream O2 was switching much faster than the left bank downstream O2 at 2000 RPM. It is kind of hard to tell with the numbers bouncing around like they do. Both upstream O2's seemed to be closer to .7 or .8 of a volt more often than they showed lower voltage.

I just realized a few minutes ago, I did not check the inlet and outlet temperatures on the left side cat. It *looks* to me from the O2 data on that side the left cat is OK.

What do you guys here think? I know my data is probably not exactly correct but this is my first time working with a code reader. I don't know whether the temperatures at the right cat are normal. I should have checked the left but it is late here. If need be I can check it tomorrow.

I drove back home from HF on a toll road, truck ran just fine at 65-70MPH. I appreciate any help I can get on this and will be glad to use my handy dandy new scanner again if we need any further data.

Thanks.

 

[yonyon]

The temperature rise tells you that cat is in fact doing something but it doesn't tell you if it's good enough. The voltages you're seeing are within the realm of functioning O2 sensors.

You want to see the downstream O2 sensors changing voltage very slowly, maybe taking that swing from 200mV to 700mV over the course of half a second or 3 seconds rather than back and forth several times per second like the upstream O2 sensors do. It's difficult to see that when your scan tool displays the O2 voltages as a number rather than plotting them as points on a graph. A graph of good upstream O2 voltages look like a jagged peaky up and down picture while good downstream voltages are a smooth curve often leveling out to a straight line and definitely do not look the same as the upstream..

The thing is: you can get by without being able to see those voltage swings or crosscounts - the voltage crossing the magic line at 450mV - because your ECM is setting a DTC that tells you you've got too many crosscounts on the downstream sensor.

The thing to look for is the fuel trims when the DTC sets. If the fuel trims are way out of wack (not close to zero) when the code sets there may be a condition that causes the code to set without a faulty cat - basically something is wrong preventing the cat from working properly. If the fuel trims are good (long trim plus short trim on the same bank add up to a number near zero) you can trust that the cat itself is actually at fault.

 

[MarkM66]

It drives fine, and mileage is the same...

You've got way more time then I do.

O2 spacer would of solved your engine light problem for $5 and 10 minutes.

 

[Trav]

As Yonyon posted get the fuel trim data. A small leak after the upstream O2 and before the down stream will drive the fuel trim crazy on that bank.
Look for leaks at joints and any brackets that are welded to the cat or pipe in that area, they can flex when the vehicle hits a bump in the road and open momentarily.

Edit: Spacers in the downstream O2 work but if the fuel trim is going off the scale for some reason its best to hunt it down and repair it. Damage to the engine from cylinder wall wash down and oil dilution can occur.

 

[Jimmy9190]

Thanks for the help guys. My new meter does check the fuel trim and it will also plot the O2 operation as a graph. I just don't know enough about it (yet) to read the graph and interpret what it means. I will try to take another look at it tonight when I get home from work and post up what results I get.

Thanks again for your help. I appreciate it very much. I don't want to replace the cat if I don't have to. I need to keep after this until I find the real cause of the problem.

 

[Jimmy9190]

I should have added here that I have a 180 degree thermostat. Truck is spec'd for a 195, however back in 2007 at only about 50,000 miles the truck develeoped a problem with preignition ping under light throttle. It is a very common problem with the Dodge Magnum engines. Dodge's "fix" for the ping is to reflash the PCM so it retards the timing 4 degrees. In the Mopar community, that is known as the "Death Flash" because it will cause a serious loss of engine power. The Death Flash will make a real dog out of an otherwise good engine, and my little 3.9 does not really have that much power to begin with.

Another way to fix the ping problem is to use a 180 degree t-stat and Autolite 3923 plugs. The 180 tstat fools the PCM into thinking the engine is not completely warmed up so the PCM will advance the timing just a little. The 3923 plug is one heat range colder than stock so the flame kernel is not as close to the piston. The 180 tstat and 3923's in conjunction completely eliminated the pinging problem. A lot of guys on the Dodge Forums run the 180 tstat for a little more performance. A lot of others like myself did it to stop the ping. The 180 tstat probably makes the engine run just a bit on the rich side, maybe that had something to do with this cat problem.

Thanks for helping me with this problem.

 

[Jimmy9190]

Ok now that I know how to get the graphed O2 info, the O2 data is more clear.

At a 700 RPM idle, Bank 1 upstream is switching quickly from .08 to .9 volts. Bank 1 downstream O2 is switching from .12 to .74, switching slower. Bank 2 upstream is switching from .08 to .80 at a fast rate, Bank 2 downstream is switching slowly form .16 to .78. All O2 graphs look like a very steady even up and down parabola type graph. I think the O2's are all OK.

The fuel trim data I am not so sure about. At idle the Short FT1 is -1.6% switching to 3.9% to 5.5%. Long FT1 at idle is steady at 3.1%.

At idle the short FT 2 is -3.1% to 1.6 to 3.9 to 4.7%. Long FT2 us steady at -3.1%.

When I hold the throttle at 2500 RPM the short FT1 stayed the same as it was at idle. The short FT2 stayed the same as it was at idle. The long FT1 was steady at -10.9. Long FT2 changed to -12.5%.

I would be grateful if you guys could point me in the right direction with this info. I knew i would not be able to easily interpret the scanner data, but this is the only way I can tell for sure what is wrong. I already spent $112.00 on downstream O2's that I didn't really need..

Thanks again for all the help here.