Re: Possibly bad cats

I got a CEL today, so I hooked up the Durametric. I got a P0430 cat conversion bank 2 code.

Right now it isn't running funny, but last week I posted regarding symptoms I assumed was a MAF (rough, no power, stalled at 3500RPM) Any guidance?

Other codes, not as pressing were:
60 central locking limit position not reached
46 Driver belt buckle
49 Passenger belt buckle

Not sure how to interpret those either.

'01S, By the way

I think you need to check your O2 sensors.

I had the same problems, same codes and it was my O2 sensors (and I needed a new MAF as well, but primarily the O2 sensors).

You need to go to a sophisticated independent - they have a tool that can read the actual sensore output ranges through the OBD II port. A bad cat code is generated when the primary and secondary O2 sensors give the computer a bad reading, but this can also happen if the sensors themselves are bad. A good tech can read the sensor output to determine if it is consistent or within range of what it should be.

While cats do go bad, it is very rare (unless you are using leaded gas - have you been putting leaded in the car?) so I would look at the O2 sensors first.

1998 986 Turbo-Look Cab
172,000 Miles
Dilithium Crystal Supercharger

Quote
IFlyLow
I got a CEL today, so I hooked up the Durametric. I got a P0430 cat conversion bank 2 code.

Right now it isn't running funny, but last week I posted regarding symptoms I assumed was a MAF (rough, no power, stalled at 3500RPM) Any guidance?

Other codes, not as pressing were:
60 central locking limit position not reached
46 Driver belt buckle
49 Passenger belt buckle

Not sure how to interpret those either.

'01S, By the way

years.

My experience is this error code more likely to occur when I fill up the car's gas tank with 'off brand' gasoline (Rotten Robbie, USA, etc.) vs. using Shell or Chevron (but with Shell/Chevon gas selling at $3.779/gallon (or higher!) Rotten Robbie or USA gas at sometimes more than $0.10 cheaper/gallon is hard to resist...). Also, colder temps seems to bring this error code up more often too.

But in all the times this P0430 error code has appeared not once has the engine exhibited any untoward behavior. One minute the CEL is dark and the next it is lit and when I read the codes I get only P0430.

The Porsche diagnostic guidelines are to when a P0430 (or P0420 -- the converter on the other bank) are present to be sure to read all the error codes and if any aging sensor codes present to replace the aging sensors clear the error codes and resume driving the car to see if the P0430 (or P0420) error code returns. If it does it is the converter, and it is worn out (worn out in this case means it can no longer store sufficient oxygen to have to process exhaust gases properly).

But unless the converter's really sick you can clear the error code and continue to drive the car with as far as I know no problems. In fact on one occasion I left the CEL on and the thing cleared on its own after a number of engine starts.

If you haven't done so recently you can try a bottle or two of Techron (use according to directions on the bottle) to clean the fuel system, injectors, and remove valve and engine combustion chamber deposits, and possibly remove any deposits downstream at the sensors even the converters. The Techron treatment might perk up/improve the engine's combustion some so the converters have less work to do. (BTW, I like to change the oil after a Techron treatment.)

The other error codes could arise from an intermittent problem with the car's central locking/security system. Generally the problem is traced to a failing component in one of the doors. (My 02 had the pasenger door locking mechanism fail and cause a rash of errors besides the obvious symptom of the passenger window not lowering when the door opened or lowering just fine but once the door open raising again. A real scary situation when one fails to note the window has risen and closes the door...)

But I would be remiss if I failed to advise you to check the cabin for signs of water, moisture, dampness. Some central locking problems are caused by water getting into the cabin and getting the security system controller wet (located under the driver's seat IIRC). Water can get in via various paths but the most common are one of the water drains -- 2 under the front cowl covers and 2 under the clamshell cover) gets blocked and rain water or car wash water backs up until it overflows into the cabin. Or one of the door window seals leaks. Check along the bottom of each door for any signs of dampness. Also, give each door a good shaking listening for any water sloshing sounds.

The rough running, no power, and an engine stall at 3500 rpms may be MAF. If the symptoms are persistent a trick is to disconnect the MAF from the wiring harness, clear the error codes (even if none are present/active) cause this resets all the long term fuel trims to their defaults then drive the car and see if the symptoms come back. If they do then the problem is not the MAF. If they do not, then the MAF is suspect #1. If the test results are inclusive you'll just have to wait for things to develop.

But with the other error codes coupled with the engine behavior you noticed I'm leaning towards water in the cabin. Also, check the rear trunk carpet for any moisture. If any water gets in there it can get the engine controller area damp -- located behind the carpet at the back (cabin wall) of the rear trunk) -- and all sorts of odd behavior can result.

Sincerely,

MarcW.

Thanks for the help!

All these things make sense, and I will go down the list one by one. I have not had any rough running since the isolated stall, and the CEL stayed off after I reset it. O2 sensor makes sense, because I have an oil leak which has been dripping directly onto the RH O2 sensor. I was going to fix that until my X5 caught fire this weekend. I guess I will have to wait until that is fixed

Your symptoms are similar to mine when my O2 sensors went bad - the symptom started out mild, and got progressively worse. I also needed a MAF, but between the two it got sorted out.

Sorry about the Bimmer. Did you know if came with a built-in toaster?

1998 986 Turbo-Look Cab
172,000 Miles
Dilithium Crystal Supercharger

to remove all the oily grime/dirt and replaced the sensor that was oiled and the one that wasn't oiled on the other side. I do not know what I did to 'cure' the oil leak. I might not have done anything but shortly thereafter the AOS went out and that was replaced and AFAIK the engine is oil tight. (The passenger side camshaft cover was off (twice) recently for some internal work and I looked over the engine and didn't see any signs of any oil leaks anywhere.

But AFAIK your car has not produced any O2 related error codes, which indicates that so far the presence of the oil on the sensor is not a problem. But it can be. And you should clean the oil and then fix the leak. Afterwards, you can continue to drive the car and see if any error codes return and if the engine behavior appears again.

Sincerely,

MarcW.

If you are trying to track down an oil leak, well known Boxster culprits with prior criminal records include:

(Note that these are not all near the O2 sensor, but I thought worth sharing based on my experience)

- The spark plug tube (relatively common)
- Rear Main Seal (relatively common on early 986s)
- Air Oil Separator (commonly implicated in smoking, but I suspect replaced more often than necessary - I am guilty of this)
- Oil Filler Tube (not that common, but a tricky one - the oil filler tube that leads from the Coolant Tank/Filler unit to the engine is very brittle and develops cracks that only open under load, leading to leaks and intermittent smoking - worth checking when you have the front engine cover off (it is above the water pump))
- Cam Cover Gaskets (not that common)

I am sure I have missed some.

1998 986 Turbo-Look Cab
172,000 Miles
Dilithium Crystal Supercharger

I posted a similar question a little while back, and after seeing your question here, I thought I would follow up with has been happening with my car.

I also had a CEL come on with a P0430 error code. I took it to the dealer, and he said I should replace both cats to a tune of > $3k. I decided I needed a second opinon. I then took it to an independent who noticed an oil leak in the spark plug tubes. He suggested fixing that and clearing the light. While I am not sure the oil leak was really related to the CEL, since I was due for new sparks anyway, I took him up on the offer. After that work, the CEL stayed off for a while but did eventually come on again -- only to clear itself after a few days. I was told that the CEL will clear itself if the problem is not present on three consecutive engine starts that result in a completely warmed up engine. The CEL stayed off for a while, then came on again, and then cleared itself again. It is currently clear.

I have also noticed (perhaps serendipidously) that the CEL appears to come on after I have filled-up at my local Exxon station, and go off after I fill up at my local Sunoco station. This seems like it should be informative to me, but I am not smart enough about this stuff to understand what it means. Could the Exxon gas just be a bad winter formulation? I understand that the error code is generated when the O2 readings do not differ enough between the pre and post cat O2 sensors. How could the type of gas make those sensors get different O2 readings? Could bad gas make the cat not work well? Could bad gas bias the O2 sensor readings somehow? I am intrigued about what is happening and would love to hear about what is going on in the engine, if someone was willing to take the time to explain it.

Since the only CEL code I get is the P0430, my current strategy is to just keep driving (on Sunoco gas) and see what happens. If the CEL stays clear or clears itself shortly after it comes on, I am going to try not to worry.

BTW -- the folks on the board, especially MarcW, were really helpful when discussing this in my earlier thread. Thanks folks.

remains as balanced as it can be.

But at a cost of $3000 for the pair I can understand the reluctance to replace both.

Also, I too have noticed a couple of things about this P0430 error. It does seem to be more likely to appear when I fill up with gasoline from a station other than Shell or Chevron. Mostly I use Shell (a station's convenient to me and has reasonable prices), with a very occasional stop in at a Chevron station. The bulk of my Boxster gas tank fillups occur at a Rotten Robbie gas station. All stations are busy so I'm pretty confident the gas in all cases is fresh.

I don't think the Rotten Robbie (or USA gas is another brand I use once in a while) gasoline is bad but based on my observation/experience there is a difference in the gasolines and Shell gasoline appears to be converter friendly or friendlier than at least the 2 other brands I mentioned above.

Another factor that contributes to the error's frequency of appearance is the weather, ambient temperature. In the warmest summer months the error never appears, but in the coldest winter months it appears every few days if I clear the error code.

Thankfully the Boxster's registration is due in May and that is usually warm or has a warm spell in it which I use to take the car in for its smog check/test. This year though no smog check is required so I get another year to think about what I might do to address this P0430 error.

Sincerely,

MarcW.

Good info on the cats, Jeff. I just replaced the spark plug tubes today, though not sure these two are related. I haven't gotten the CEL for a while, but I will keep what you said in mind.

what's it cost to replace the MAF? DIY job or go dealership/independent? If its a DIY... what special tools and how much is the part? Thanks!

MAf replacement https://sites.google.com/site/mikefocke2/checkenginelightcausedbymassairflowsensor

I'm far from a mechanic. 15 minutes with the purchase of a ~$20 tool I bought from Sears. But before replacing, try to clean it. Unclip, 2 special screws, lift out, blow a $6 can of MAF cleaner from an auto parts store into the sensor parts for a few seconds. Dont touch em or wipe em. Wave in the air to dry, replace, reclip. Drive for a few days and see if everything resets itself.

Thanks Mike, you remember what the tool name/size you purchased from Sears? I will give it a go before shelling out the cash for a new part. Cheers, Russ

Picture of the 22mm tool choices is on my web site under the O2 sensor article. Choice of 2. Either available online at less than $30.

Google "oxygen sensor tool" and you'll see dozens of offers for the same basic designs.

Pictures and numbers for the security torx set I bought are in the MAF article at https://sites.google.com/site/mikefocke2/checkenginelightcausedbymassairflowsensor

Just what i needed... thanks.