Jump to content

The RennTech.org community is Member supported!  Please consider an ANNUAL donation to help keep this site operating.
Click here to Donate

Welcome to RennTech.org Community, Guest

There are many great features available to you once you register at RennTech.org
You are free to view posts here, but you must log in to reply to existing posts, or to start your own new topic. Like most online communities, there are costs involved to maintain a site like this - so we encourage our members to donate. All donations go to the costs operating and maintaining this site. We prefer that guests take part in our community and we offer a lot in return to those willing to join our corner of the Porsche world. This site is 99 percent member supported (less than 1 percent comes from advertising) - so please consider an annual donation to keep this site running.

Here are some of the features available - once you register at RennTech.org

  • View Classified Ads
  • DIY Tutorials
  • Porsche TSB Listings (limited)
  • VIN Decoder
  • Special Offers
  • OBD II P-Codes
  • Paint Codes
  • Registry
  • Videos System
  • View Reviews
  • and get rid of this welcome message

It takes just a few minutes to register, and it's FREE

Contributing Members also get these additional benefits:
(you become a Contributing Member by donating money to the operation of this site)

  • No ads - advertisements are removed
  • Access the Contributors Only Forum
  • Contributing Members Only Downloads
  • Send attachments with PMs
  • All image/file storage limits are substantially increased for all Contributing Members
  • Option Codes Lookup
  • VIN Option Lookups (limited)

My 997 bucking/misfire


Recommended Posts

Dear all,

Im new to the forum and i have a problem with my car.

I have a carrera 997 2006 model. I didn't use my car for the last one and a half year. Last week i change the battery and also i changed my catalytic converters. I install 200 cell sport catalytic converters 63 mm tubing. I notice that the car bucking/misfire at low rpms. For example when i have 3rd or 4th or 2nd gear and the rpm is around 1.500 and when i push the fuel pedal (accelerate) the car bucking (no check engine light) for 1 or 2 seconds. If i push full the throttle all is fine. In high rpms everything works fine.

Any sujestions?:/ btw sorry for my english:/ btw my car is automatic transmission.

Link to comment
Share on other sites

Does the problem happen when the engine is warm? My car occasionally hesitates when it is first started and I'm pretty sure the problem first appeared after installing 200 cell cats. But is is fine after a few minutes of running. I'm assuming it is caused by reduced backpressure and the computer doesn't compensate for it while it is still in open-loop mode while the O2 sensors are heating up. But that is just my theory.

Link to comment
Share on other sites

  • 2 weeks later...

Hi, Loren,

Engine light turn on today. I scan it with my lemur bludriver and found the error: P0430 Catalyst System efficiency Below threshold Bank 2. Is that code have to do with my misfire? If yes why the engine light turn on today and not from the day tha the problem

Start?

Link to comment
Share on other sites

  • Moderators

Hi, Loren,

Engine light turn on today. I scan it with my lemur bludriver and found the error: P0430 Catalyst System efficiency Below threshold Bank 2. Is that code have to do with my misfire? If yes why the engine light turn on today and not from the day tha the problem

Start?

Hi, Loren,

Engine light turn on today. I scan it with my lemur bludriver and found the error: P0430 Catalyst System efficiency Below threshold Bank 2. Is that code have to do with my misfire? If yes why the engine light turn on today and not from the day tha the problem

Start?

It could be triggered by the misfire as the P0430 indicates that the cat is no longer doing its job. Couple of points: The CEL turns on when a code error becomes "active", but it could have already been there as a "pending" code while the DME decided if it had reoccurred often enough to be a real issue. A second comment is that cats usually do not cause a misfire; but rather misfires cause cat codes to trigger. Thirdly, P0430 codes are sometimes triggered by O2 sensor problems or the EVAP system, and in particular the canister purge valve on the EVAP system, which can cause a vacuum leak, and thereby a misfire. Lastly, you need to have this vehicle scanned with a Porsche specific scanner (Durametric, PIWIS, PST II); many times codes generated by other systems turn out to be different when scanned by one of these systems.

Link to comment
Share on other sites

  • Moderators

Thanks all of you for your reply.

I will bring the car to a porsce dealer.

Btw the car has only 45000 khm.

So you beleive the problem is not with the 200 cell catalytics, due to the low back pressure?

It can be a problem with the cats themselves, but I rather doubt it is because of low back pressure. Why did you install the aftermarket cats in the first place?

Link to comment
Share on other sites

My vehicle sustained an impact at the rear end.

The local porsche garage said that i need mufflers and cats.

I bring the car to another garage and he said me that my mufflers it was fine (no damage). And i only change the cats. Because the original was 2,500 euro each i decided to purchese the x pipes 200 cell 65mm from designt tek. For only 700 GBP. I have no idea what to do:/

Link to comment
Share on other sites

  • Moderators

My vehicle sustained an impact at the rear end.

The local porsche garage said that i need mufflers and cats.

I bring the car to another garage and he said me that my mufflers it was fine (no damage). And i only change the cats. Because the original was 2,500 euro each i decided to purchese the x pipes 200 cell 65mm from designt tek. For only 700 GBP. I have no idea what to do:/

Interesting. Here, we often buy used cats from front end wrecked cars to keep expense down. While a single new three way cat can cost upwards of $1700 (US) or more, we can often find used ones in good shape for as little as $500-600 (US) total for both sides. There is even a market here for totally useless three way cats, we sometimes get $50-75 (US) each when we sell them to recyclers.

Link to comment
Share on other sites

  • Moderators

Do you know any website that sell used original cats for my car?

Btw i forgot to mentioned that the car was in my garage for almost 2 years with flat battery.

The flat battery should not be a factory if it has been replaced the electrical system is now functioning correctly.

There are several sources here in the US (https://sites.google.com/site/mikefocke2/listsofsources ), but I would be looking for something closer to you, perhaps in Germany, otherwise the freight and import cost might exceed the savings.

Link to comment
Share on other sites

  • 3 weeks later...
  • Moderators

Hi all,

They call me today from my local porsche garage and said that i need new fuel injectors and fuel pump due to the reason that the car was sitting in the garage for 2 years the injectors are daged and is the reason for the misfire.!?!?

Definitely possible, fuel goes stale and gums up everything if it is allowed to sit. In the US with gas containing 10% ethanol, the problem is even worse because the ethanol retains a lot of water and cause corrosion in the fuel system as well. If you are going to store a car for a prolonged period, a quality fuel stabilizer like StaBil is highly recommended, and will prevent fuel degradation for as long as two years.

Link to comment
Share on other sites

  • Moderators

Do you think is good idea to try fuel injector cleaner before to change them?

It might help, but if they are corroded or severely varnished, it is not going to do much. Normally, I would suggest pulling the injectors and sending them to a shop that specializes in refurbishing used injectors, they have more specialized equipment to both properly clean and test them.

Link to comment
Share on other sites

  • 5 weeks later...
  • Moderators

Hi all,

They clean my injectors. The problem is still there. They say me that the problem is the low backpresure due to the 200 cell cats 63mm. Is that possible?

I can see the problem being the cats, but not from back pressure. The DME is expecting to see a certain conversion rate (mentioned above) differential measurement between the O2 sensors before and after the cats; the code you are getting is exactly for that. How back pressure figures into that problem would require an explanation from whomever is working on your car, but the code is for a low conversion rate, a common occurrence when a cat is dead or dying.

Before changing out the cats, be sure the sensors are working correctly.

Link to comment
Share on other sites

  • Moderators

Is better to change the o2 sensors before changing the cats? The porsche factory was working on my car for 2 weeks now:/ didn't check the o2 sensors? :( they said something about the pressure and the ecu reader, and also said that these cats had bigger tubs than my original.

No, it is better to test the sensors before doing any parts changing; too many people assume it is the sensor, which are expensive, and start swapping parts before they really know what is wrong. If you have access to a Porsche specific scan tool (PIWIS or Durametric), you can read the sensor output from the scan tool. If you do not have the scan tool, you can still read the sensor voltages using a digital multimeter. You can also ask the Porsche shop that has been working on the car what sensor readings they got when testing the car.

Here' some background information on how the sensors and cats interact, both correctly and when the cats go bad and would throw the 0430 code. The data if from a Boxster, the your car would work exactly the same:

ThreewaycatandO2sensoragingdiagnostics3_ThreewaycatandO2sensoragingdiagnostics_zThreewaycatandO2sensoragingdiagnostics2_

P0430Image-1.jpgP0430Image2.jpg

  • Upvote 1
Link to comment
Share on other sites

JFP is right on track! If the O2 sensors pass the next thing to test the CAT. I think you be better off going to a professional for this. The best test for that is whats known as the Intrusive test. On Porsche its not Intrusive because the MFG has a bolt hole to test from. Also I am not a fan of aftermarket CATs or sensors because they are not made with as tight specs. as OEM. Also most aftermarket CATs are smaller and do not have as much precious metals in them to work like OEM.

When I was doing smog related repairs if the car owner would not let me use OEM parts I would pass on the job period. There is an old saying you get what you pay for. You cant skimp on aftermarket CATs or sensors for Porsche and even Honda as there specs are as tight as Porsche and will throw P0430 codes all day long.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.