woodhead

Run into P0430 code, and will try the Techron then. Wish good luck for me.

Macster

A lot of water has passed under the bridge since 2012...

You can try the Techron to see if it addresses the P0430 but I don't think it will.

To recap P0430/P0420 is the converter operating below efficiency. The factory OBD2 diagnostic say to if the P0430/P0420 code is accompanied by any aging O2 sensor codes to replace the sensors indicated clear the codes and road test the car. If the P0430/P0420 error comes back to replace the indicated converters.

There is only one other possible cause listed: A leak in the exhaust. So you must be sure the exhaust has no leak either before or even after the converter and the #1 and #2 O2 sensors.

In the case of my Boxster I was able to get the car through SMOG several times even with the intermittent P0430 error. I was fortunate (?) the converter error code arose because the converter proved to be loose, the converter "brick" had come loose -- probably due to a hit from road debris some years earlier -- and would under some conditions -- rough road/sharp turn -- move out of position which would cause the error.

But it would somehow return to its correct (enough) position and work well enough to make it through SMOG. While the switch from discount gasoline to Shell V-Power seemed to make the error less frequent it was by no means a cure.

The last smog test I had a "scare" in the car failed due to excessive emissions. I think the problem was excessive hydrocarbons but I really don't recall now. I do recall I had as is my routine I had driven the car plenty before the test to ensure everything was plenty hot but still the car failed. I spoke with two Porsche techs -- separately -- and both expressed surprise the car failed smog and both suggested I take the car out on a longer drive and not their words but give it something like an Italian tune up.

Long story short I did this and just a few hours later had the car retested and it passed no problem.

This close call scared me. The last thing I wanted was the car to be flagged and then perhaps come in for extra special attention, every year testing, or whatever.

In addition there was a deep low volume knocking from the engine (it seemed) when cold and a horrible buzzing noise when everything up to temperature.

Had this looked into hoping it was a loose heat shield and the tech reported the noise was from the converter. Apparently the situation had worsened to the point the converter brick was knocking about when cold and then buzzing when hot. I didn't think the converter brick would hold up much longer and would begin to physically fail. Generally the brick is a pretty delicate item, in some cases made out of "glass" (ceramic), and can break up and this can lead to a blocked exhaust.

What I did was to buy a pair of used converters (exhaust manifold + the converter) but not before making sure both had nothing loose inside and were not shedding bits of brick -- and after my inspection I then handled the two used exhaust manifolds like delicate crystal -- and had the tech swap these for the original ones. Afterwards the car was quiet and not one P0430 (or any other exhaust related) error code.

Try the Techron. My fingers are crossed it will help but honestly I don't hold much hope. Techron does work as has been my experience when I switched from Shell V-Power to Chevron Supreme. After about a tank of Chevron gasoline the Boxster engine was running noticeably better.

However, barring a minor miracle I think you are faced with replacing the converter associated with the P0430 error code.

woodhead

Thanks for the super detail reply.

I think my Cat are nearly die, but still works. 3 months ago, the car passed smog by reset the error code with a OBD reader. And this time it runs 200 miles after my previous reset.

If Techron works, it's a surprise. If not, I will try to find a Cat from ebay.

Some more questions:

1. Must I replace the Cat in both side? or the broken side only?
2. If not, which side is the P0430 Cat? Left or right?
3. If I purchase a Cat from ebay, what is the labor cost around?

Thanks!

mikefocke

Brett posted on PPBB: The O2 sensors do just that, sense the amount of O2 in the exhaust gas relative to the amount of O2 in ambient air. Perfect combustion of a perfect mixture of air and fuel (around 14.7/1 air/fuel ratio) leaves behind only CO2 and water as products of combustion. All the oxygen gets consumed in the combustion and combines with all the carbons and hydrogens. If there is not enough fuel (lean mixture), then all the fuel gets burned leaving some oxygen left over. Conversely, if there is too much fuel (rich mixture), then all the oxygen gets burned leaving behind extra hydrocarbons (fuel). Now an oxygen sensor outputs a voltage between 0 and about 1 V depending on the difference between the amount of oxygen in the exhaust and the amount of oxygen in normal air. If there is a lot of oxygen in the exhaust (lean mixture condition), the sensor outputs close to 0 volts. Conversely, if there is no oxygen in the mixture (rich condition), then the output is close to 1 V. These O2 sensor voltages are read by the computer. This is the feedback loop that tells the computer how the engine is performing with regard to air/fuel mixture. It's impossible for the computer to hold the exact perfect air/fuel mixture constantly, so the way mixture control is designed is for the computer to continually adjust the mixture from very slightly rich to very slightly lean and back again using feedback from the pre-cat O2 sensors. This means that the pre-cat O2 sensor signal will oscillate back and forth from high to low to high to low voltage as the computer adjusts the mixture. In a normal running engine at idle the signal goes from low to high voltage and vice versa about every 1 second, with a transit time from low to high (or vice versa) being about 200-300 milliseconds. This transit time is important because as an O2 sensor ages, the transit time gets longer, and eventually it can get too long such that the computer will call it a malfunction and signal a check engine light and fault code for a slow responding O2 sensor. O2 sensors need to respond to mixture changes quickly so that the computer can keep up with the proper mixture adjustments. So the bottom line is that the pre-cat O2 sensors should oscillate between about 0.2 to 0.8 volts regularly (about every 1 second at idle) in a healthy engine. The post-cat O2 sensors are identical to the pre-cat O2 sensors (same voltage outputs). They are there only to monitor the performance of the catalytic converters. So, as discussed, the pre-cat sensor signals are oscillating between 0.2-0.8 volts. Once the exhaust gasses pass through the catalytic converter, most (all, in theory) excess fuel (hydrocarbons) will be combusted thus reducing hydrocarbon emissions. The cat uses oxygen in the exhaust to combust the fuel. So what you end up with in the exhaust after passing through the cat is a gas mixture that is reduced in hydrocarbons and reduced in oxygen relative to the mixture entering the cat. The post-cat exhaust gas mixture should be CONSTANTLY low in oxygen if the cat is doing its job of burning excess fuel. Therefore, the post-cat O2 sensor signal should be a constant lower voltage reading (not oscillating). So, if the post-cat O2 sensor is seen to oscillate just like the pre-cat O2 sensor, that means that the post-cat sensor is seeing the same gas mixture as the pre-cat sensor meaning that the catalytic converter isn't doing its job of burning excess fuel. The computer monitors the post-cat sensor and compares it to the pre-cat sensor. If the signals are similar, it assumes the cat is bad.

Macster

If you identify just one "bad" converter you only need replace that one. However, due to the miles on my car's original converters I replaced both with ones from a salvaged car. I do not know how many miles the converters had covered but I assumed given my car's very high miles it was less than the factory converters on my car had covered. Besides I wanted to try to keep the behavior of both banks the same. My concern was with one "old" converter and one "new" converter there would be a significant difference between the fueling of the two banks.

Have to mention too that I picked up the 2 converters so I could give them both a shake to make sure nothing loose inside and nothing falling out. Then I handled the converters with kid gloves. They were carefully stored in the Boxster to not bang around or bang into each other.

If you order a replacement you run the risk of it being bad out of the box due to being used and bad or if new being mishandled during shipping.

I'm sorry but I simply don't remember which converter the P0430 error code referred to. That is I believe it was the bank #2 converter which I think would make it the bank on the driver's side of the car (a USA car) because cylinder #1 is the cylinder to the left of someone looking at the engine from the non-power output end of the engine, but you need more than my questionable memory to go on if you plan on ordering just one converter.

I do not recall the amount of time (labor) it was to swap both converters. If I had to make a WAG, maybe 2 hours. Word I get is invariably -- unless the car is relatively new -- one or more exhaust manifold bolts/studs break and the tech has to take time to remove the broken hardware. They are quite practiced in doing this but it does add time to the job.