haulinkraut

I had my car in getting paint work for a week after a clown in a pickup truck scratch my door with his bumper. I got the car back and it is misfiring and hunting after the car haa been driven for a half hour or so. It is definately temp related. It gets progressively worse the warmer the car gets. So i unplugged the maf with the car warm and it idles smooth as can be. I plugged the maf back in and the rough idle hunting comes back. I replaced the maf and air filter and that did make a very small difference. I reset the codes and trims with an obd reader and also un-hooked and reconnected the battery with no change. I checked the plugs in the engine area and the battery area and they appear good. The body shop did have the battery disconnected and ot appears good.

If it were an intake leak i would expect it to be there all the time regardless of temp. Another weird thing is the misfires seem worse with the AC off. Alternator? Battery? Coils? Any thoughts?

FYI: plugs, maf and dvs are new.

Macster

Is the check engine ilght on and are there any any error codes?

If the symptom is misfiring and disconnecting the MAF didn't help and there are no other error codes (like something related to the VarioCam timing/lift system) I suspect the body shop after it was done washed the heck out of the car and got the engine real wet.

The symptom you are seeing is I believe due to the coils most likely being wet. They may be past their replace by date too. (Or if they're new one or more might not be secured to its plug sufficiently.)

If they're not new, then they may be dry and cracked and very sensitive to any water that can cause the coils to deliver unsufficient spark.

That the symptom gets worse as the engine heats up suggests the water vapor is increasing and this is affecting the coils.

So, you should check every coil and replace any that look old, dry or show signs of cracks, etc. But sure the electrical connections of the coils to the plugs and the coils to the engine wiring harness are good and tight too.

But I reserve the right to change my mind once I know what the error codes are.

As for an intake leak...

What do the short and long term fuel trims look like while the engine's idling? If an intake leak they'll be biased towards the rich side.

Was anything done to the engine just before the car got bumped?

Unlikely to be an intake leak unless somebody was at the engine while it is was in for body/paint work.

Sure, intake leaks can happen on their own, but... Well, I guess it doesn't hurt to eliminate the possibility of a leak. I used to use carb cleaner spray around the intake and if there was a leak the engine would react when the spray hit the leak.

Lastly, a weak battery can cause all sorts of problems. Be sure the battery is in good shape. Test it and then let it sit a few hours and test it again. This is how a tech id'd a marginal battery in my Turbo. The symptom was just a slow cranking and a bit of a reluctant start. But the battery wasn't that sick though it probably soon would have been.

Sincerely,

Macster.

haulinkraut

No CELs. I checked the car with durametric today and found that the car had a P0135(bank 1 precat O2 heater). Oddly enough the regular OBD II reader I used didn't pick this up at all. The car was intermittently getting cylinder 1 and 2 misfires consistent with the idle hunting. It seems plausible to have an O2 sensor heater going open when things heat up, but to be registering misfires on only 2 cylinders of that particular bank seem strange. Unless those are the weaker coils and are only showing up when the O2 sensor causes the car to dump fuel into the cylinders. The misfire count is only around 10 so that may not be the cause as much as a symptom. I plan to change both primary O2s regardless and see where that gets me.

Kevin

Bad Plugs

Coil Pack

Fuel pump failing

Bad MAF

Bad O2 sensor

Intake leak

Start at the top and work down.

Macster

I've never used the Durametric tool but I'm pretty sure you can view O2 sensor voltages in real time and doing so could help you determine if one or both sensors are acting up.

Actually if one side is working ok this helps because it provides one with a working sensor to compare to the reading from the other suspected misbehaving sensor. Also, the bad sensor may not be bad all the time. These things don't always fail and fail hard. My experience with my Boxster and its sensors is that the sensor will get worse over time, as I drive the car for say 30 miles and then get so bad the engine controller will set the check engine light and log an error code. I'd shut the engine off then pull the code later and check the sensor and it would be working fine. After awhile I left the code reader/data viewer hooked up and as I sensed the car had been driven long enough I started to when I could view the sensor voltages and could see the sensor start to provide voltage values that I knew were wrong.

Anyhow, replacing the 'primary' or #1 or the sensors ahead of the converters sounds like a reasonable step. I don't like to throw parts at a symptom but there are worse things you can do in this situation.

Be sure you source the right sensors. I believe the Turbo's #1 sensors are wide band sensors and these are not interchangeable with the rear sensors and narrow band sensors should not be used in place of the wide band sensors.

Wide band sensors helps the engine controller more precisely control the air fuel mixture to the engine. Very critical for our Turbo engines.

Sincerely,

Macster.

haulinkraut

I don't usually like to throw parts at a problem either. But in this case it is a chicken or the egg thing. A little FYI about these O2 sensors. You can buy a Bosch plug and play replacement for the primary pre-cat O2s under Bosch part number 17044 for $96 from autozone or similar retail suppliers. The don't keep them in stock usually but they can order them. The OEM O2s are bosch and the only difference is the price and they factory ones usually have the Porsche part number on them. Functionally they are identical. No wiring needed at all

The secondary (post cat) is also available as a plug and play under Bosch part number 16205.

Macster

As long as you're sure you are putting in comparable O2 sensors it makes no difference I guess how or from where you source them. Some have suggested that some sources deliver 'seconds' or parts that are not otherwise as good as 'factory' even though in some cases the parts are produced by the same company that makes the 'factory' parts.

I have no direct knowledge one way or the other.

You'll know soon enough if the sensors are quality or not.

Just hope the new sensors address the symptoms and no more appear.

Sincerely,

Macster.

haulinkraut

No seconds or rejects here. They are factory Bosch plug and play replacements. The only difference with these is the lack of a Porsche box. When I was in the Audi B5 S4 community I was in a bind and needed primary O2 sensors on a weekend because the car was my daily driver and I had to settle for a splice in Bosch generic "equivalent" from Autozone. I bought both for dirt cheap and was shocked when I got the failed sensor out and found the same Bosch numbers on the new sensor part as the factory original Audi part. The sensor was 100% identical to the factory item. Having an electrical and electronics aviation background I sourced environmentally safe Raychem type splices and spliced them in. The sensors were functioning perfect for 4 years and 3 of those were at stage three 22psi boost levels. They may still be in the car now. Not all parts are something that you can take the cheap way out on, but some things out there are standard regardless of car manufacturer. You just have to do your homework before you try to cheap out on something.

On that note I have heard of online factory part's places selling factory parts that are of previous revisions, but never rejects or seconds in it's true sense. The factories will change revisions sometimes for manufacturer changes and sometimes it is due to design flaws too and can be a risk with online parts warehouses. The loose label of "OEM" has become a blank check for anybody who builds a particular part to pedal theirs as OEM when it is not even close.

Mikelly

Craig, As a "comparison", here's what pelicanparts partnumber is for the upstream cats...

996-606-128-00-M14 And they want $126 each for theirs, which are also BOSCH.

Hope you get it fixed man! How's the son doing?

Mike

Kevinmacd

An O2 heater problem should only be apparent as the car is warming up. A preheater allows the sensor to start operating sooner before the exhaust temps heat up the sensor. This allows the O2 sensor to operate in closed loop mode quicker, reducing exhaust emissions. By the synptom you outlined an O2 heater open circuit should not provided a worse driving condition once fully heated buy the exhaust temps. Unless of course the diaganostics cannot discriminate between the heater circuit and sensor circuit.

MICHAELWWW

Thanks, this the only thread that comes up if you search p0135. My 2009 c2S threw this code on a CEL that came on and off in a days time. The dealer seemed perplexed to see this on a 997.2. The light had been out for a month and the car was running fine. They said if it came back on they would do more checking. (I was in for a spare key and they checked the old code) any thoughts on what appears to be an odd code for a newer car?

Macster

Wonder why the dealer was perplexed? The code is a standard OBD2 emissions code, related to fuel and air metering. I assume the dealer was using a Porsche supplied PIWIS2 which ought to be able to read codes accurately from Porsches.

AFAIK all modern Porsches have heated O2 sensors to warm them up quicker and keep them warm.

Sincerely,

Macster.

Kevinmacd

Heater on the O2 sensors is only used to quicken warmup, the engine is in open loop mode prior to the
O2 sensor warm up, Which means the ECU does not use the sensors for intial cold start, Once the sensor reaches 600 deg F, the Zirconia, a white crystalline oxide becomes active to measure O2 in the exhaust. Since the exhaust is above 600 deg F once warmed up, the heater bascially becomes useless. So in principle the heater circuit allows for quicker warm up which allows for faster switiching to close loop mode, which uses all inputs from all sensors to adjust fuel air ratio.

MICHAELWWW

Unless I wasn't getting the whole story. That is the code he gave me but he alluded to the possibility it could be more than just a bad sensor??? Perplexed in the sense that they had not seen this code on an 09 with only 23000 miles. Said something like it is usually seen on a 996(not sure) was happy with the benign explanation and was heading to work.

Macster

My info is the sensors (at least in the case of the pre-2004 MY Porsches) are heated all the time. But I can't find anything definite on that.

Even if I'm wrong about the heaters being on all the time, my original comments apply: Paraphrasing (and expanding on what I said previously), no way the dealer should be perplexed. The O2 sensors have heaters and whether they work just at cold start or all the time they should be working.

I'm perplexed the dealer is perplexed.

Maybe the dealer is cutting back on say OBD2 training for its techs? I visited a dealer a while back and then again more recently and each time found one of its techs out (down in the LA area) attending a week long OBD2 training.

The class runs a week and costs several thousand dollars (I wanted to take some classes but they are closed to the public).

Sincerely,

Macster.