Sooty Exhaust

Hello Folks, I've been struggling with this issue and I hope y'all can lead me towards a solution. The passenger's side tips become very sooty after a few 100 miles. Originally I thought I may be suffering from bore scoring, but I had the blocked scooped and the shop concluded it was not oil on the tips and the rest checked out. Long story short, bank 1 runs rich. The shop stated the car had two stored o2 sensor faults. I replaced them myself and it reduced it, however, the exhaust soot still builds up. Things I've addressed: -Cleaned the Mass air flow sensor -replaced the plugs -replaced the o2 sensors There is no check engine light but I have a feeling I should replace the coils. Thought?

I believe a few folks on here have talked about injectors failing and causing too much fuel; they specifically mentioned it bore washing and leading to scoring but this might be an early symptom?

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+1^^^

I see, thank you. A little more than a year and this joy has become too much of a money pit. : /

Rather than throwing money, labor and parts at it, spend some money to have it tested for fuel trims, cold and hot air fuel ratios...generally speaking an emissions test on the tailpipe (both tailpipes for comparison of Bank 1 and Bank 2) . Since it is not throwing a CEL and thus a code you can look up, I would do some diagnostic work first. And, do you live in a cold climate? Short trips? The soot and condensation is most prevalent when engine is cold start, the air/fuel ratio is rich for running a cold engine, and the cats have not warmed up so condensation is produced. That is why in cold climates you always see steam coming from the exhaust of all cars. Condensation is a product of combustion, but the warmer the car engine becomes, the air/fuel ratio drops, and the hot cats burn it off. The O2 sensors are very sensitive pre and post cat and will throw a CEL if something is wrong. Since it is not throwing a CEL, you need to diagnose the way the engine is running.

Can some recommend a shop in San Jose, CA? I will post the printouts from the shop this afternoon.

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+2, injectors for bank 1 won't be a crazy amount of $$. Does the DME pick up injectors that are stuck open? I've read on here it's a somewhat common issue.

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San Jose Ca is certainly not a "cold climate"... Regardless, the recommendation for diagnostic work is a good one. Throwing parts at these cars is NEVER a good idea, and as you've experienced gets very expensive very quickly

Replacing bank 1 fuel injectors on a car that has too much fuel hitting bank 1 is hardly "throwing parts at a problem." Even with diagnostics, you're going to need to sack up at some point and eliminate the most likely variable and retest.

My suggestions were based on CA having strict emissions testing, so just about any decent auto repair shop should have a air/fuel ratio tester. Stick it in the tailpipe and get a reading. Okay, so Bank 1 is running rich...then figure out if it needs a bottle of Techron and a good hot high RPM run (the ole Ferrari tuneup to blow out the carbon)...or replacing fuel injectors at $250 a pop (that's Bosch rebuilt green injectors/Pelican Parts). He said the plugs were replaced...were they replaced with the correct ones? Things that come to mind...bad spark plug(s), a sticking fuel injector(s), weak coil pack(s)...and so on. My wife's Mini Cooper exhaust gets sooty because mainly she drives it 15 minutes to work. When it starts to look really sooty, clean it up, bottle of Techron in the gas tank, and then I go drive it for 30 minutes in Sport mode using the paddle shifters. Cleans that crap right up and stays that way for weeks. Repeat as necessary....

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Perhaps it is normal. My car does the same through all 4 exhaust tips. Due to the soot buildup, I thought the plugs would be fouled pretty badly. Hence I did a plug/coil change. The plugs I pulled out were in very good condition. Apart from a slight grayish color, the plugs looks like new and this was after 50K miles. That black spits you saw collected on the floor were just condensation due to cold starts and the catalytic converter doing its job. I would worry about it.

Warehouse 33-new Bosch injectors $34 ea (996 606 122 00) and Rennlist 10% discount (RM Euro about same price)...cheaper than testing and refurbishing. +1 on check trims and injectors. If pre- and post-cat sensors check out, injectors are a suspect. CEL won’t trip below 30 or 33% miss-trim IIRC. You can try to reset the fuel trims as outlined in other posts. Ahsai has helped lots of us with O2 sensor function questions, so research his replies for more help. The Knowledge Gruppe has a Technical Bulletin addressing injectors in RND engines. Charles graciously posted it in another thread. Go to RNDengines.com for that TB. Those symptoms can happen below 50F. Does one bank do this exclusively on every cold start, or do both banks spit water/soot at different intervals during the approximately 2 minute SAI cycles? You might get some fuel smell and smoke puffs during start. The water drops start after about a minute or more? 3-4 minutes after car started, everything except your heart running at idle? Ask me how I know.

Couple of more questions. Does the SAI pump run when you start it up? Since you did the MAF cleaning, plugs and O2 sensors, have you done a reset of the DME by disconnecting the negative lead on the battery for a few minutes? That returns the DME to default values and by driving it after that, the DME re-maps based on current values being supplied by the various sensors.

IF you determine that your injectors are at fault - check into having them rebuilt. I honestly don't know what the options are for the 996 - but I had all the injectors from my RX-7 rebuilt and it was fairly reasonable. This was probably 12 years ago - but I used Witch Hunter Performance - https://witchhunter.com/ - they provided before/after flow test results and turned them around very quickly at a reasonable price. Cheers Charlie

Thank you, thank you, folks. -Air pump was replaced #1 shop: the plugs pulled were in good condition and replaced with oem recommendation. I was told not to change the coils unless they went bad. I wish I would have just changed them in the process. #2 shop - - they stated that is was normal. : / #3 shop - they concluded the o2 sensors on bank 1 might be causing the sooty. I opted to replaced them myself and I purchased them from Pelican. I did not disconnect the battery after but I will try it this weekend. Is there a specific procedure to doing it? Soot only builds on the passenger tip. I have a short 10 mile commute, but drive it hard and changed my route to ensure I get the tempretures up. Again, is there an shop in San Jose, CA that can address such needs?

Disconnect the negative lead on the battery and wait 15 minutes. Good time to clean out the exhaust tips with some Goo-Gone...spray up into the exhaust tips and clean them out. I really stuff shop towels up in the exhaust tips soaked in Goo-Gone to clean them out. After 15 minutes, reconnect negative battery lead and go for a drive. The DME will re-map based on current conditions and sensor readings. A 10 mile commute is probably not really enough to heat up the engine and clean things out. Go for a long drive, 30 minutes or more at a highway speed. Then check your exhaust tips. Probably will be much cleaner after that. A bottle of Techron in the fuel tank would not hurt anything.

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Thank you for the mention. Here is the link to the injectors. https://www.warehouse33auto.com/BOSC...996-606-122-00 -Jason

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That's how my motor "blew it's top", requiring that I replace the injectors (again), the MAF sensor, intake gaskets, etc. Scary when you crank and hear an explosion.

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There is no such thing as a cheap Porsche.

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no affiliation but they are linked to L & N's website as Certified Retrofit Installers http://europeanautotechsr.com

Well, there you have it and now you know what is wrong. Bank 1 O2 sensors signal implausible, plus a few oil leaks. What brand/type of replacement O2 sensors did you use? It threw those error codes and your CEL was not on?

I replaced both oxygen sensors with Pelican's Part #: 993-606-118-01-M14 Yes, no check engine light. - I disconnected the battery - Filled up and added Chevron fuel treatment and went on a spirited 150mile drive - same results, soot build on the passenger's tip only

Is it very humid where you live? That looks like water to me. If it was coolant, the plugs would show some signs from that, or from oil. Why only passenger side, no idea, but I think that my car also has more soot / black dirt on the right side tip. Maybe the bank 1 burns little more oil than bank 2. Thus more soot that soaks the moisture that is inte exhaust gasses. IMO that's just a moisture coming out with the ex gasses.

So you had the initial diagnostic and replaced both of the O2 sensors on Bank 1? The Pelican Part number you gave is: Oxygen Sensor, (After Catalyst) Part #: 993-606-118-01-M14 There are two different O2 sensors required on each bank, pre-cat and post-cat: 99360611801 (up to 99) Post Cat 99660611800 (year 00 and up) 99360612801 Pre-Cat http://www.autoatlanta.com/porsche-parts/hardparts.php?dir=996-99-05&section=202-00 Did you replace both O2 sensors with the correct pre-cat and post-cat sensors?

Hello and thank you all. Yes, I purchased both different sensors for bank one.

If you have an Instagram account, I have a video of the soot under a cold start. I�m the_unloved_porsche

Stop filling it from the GREEN HANDELED pump. Well somebody had to say it.

sounds like maybe the bellows for the oil separator??? Vacuum leak on one bank?

AOS is new. Local shop installed a new MAS and cam sensors as they were not within specs.

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I thought the two O2 sensor (Porsche) part numbers were due to the different harness lengths. Are you saying the values are different? I used Bosch universal ones for pre and post cat. You cut them to length.

Hello, if you look at the part numbers, there are two different oxygen sensors, one has a black and other a gray plug. And even further, they differ between certain years.

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That is because on each side of the engine compartment there is a pre cat sensor connection for that bank and a sensor connection for the post cat from the opposite side bank. In other words. If you are looking into the engine compartment in the area behind the passenger tail light, you will see two connectors, one gray and one black. One is for the pre cat O2 sensor for the passenger side bank. The other connector is for the driver side bank post cat. And vice versa on the other side. I installed Bosch universal sensors in my '99 which come with no plugs. I had to splice the factory plugs(one black/one gray) onto the bare ends. I believe the different part numbers (Porsche) are due to the harness lengths being longer/shorter and black/grey so they will be plugged into the proper connector.

As others have mentioned do your diagnosis tests.Don't just replace parts perform the test procedures per shop manual. It looks like you have some ego codes get shop manual and perform pinpoint tests.If you replaced the ego sensors but didn't clear codes and reset strategy you need to do that.

https://rennlist.com/forums/996-foru...-roller-2.html Good thread on the topic^^

Has any of you guys ever consider the 997 Vertex rebuilt engine for the 996? https://www.vertexauto.com/porsche-9...-p-412036.aspx

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Good lookin' out Bill, might be just the info he's lookin' for -- just read that thread and am adding injectors to the list of PM.

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The OP doesn't need a new engine just yet. There's time to save it. The manometer readings that were posted looked pretty good.

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Coolant Temp Sensor? Also do you still have those RH cup wheels for sale? Can�t figure out how to PM. Asking for a friend.

Hello folks, Here is the update: The engine was out and the following items were replaced: -Chain guides and seniors - cam potions sensors - cam actuators - lifters - new MAS - new plugs - new coils - (which may be causing a static) - New AOS - and a few other things The problem is still there. I encourage my mechanic to change the injectors but he said they were fine. I am dropping the car off again. I will be showing him this thread. He insists the sooty tip and running rich is fine but I think it might be hurting my engine to the point that I will need an engine rebuild due to his inability to fish out the problem.

Boost Meizer - I sold the CCWs and RH Wheels some time ago. Base on the issues I have been having with my 996, I will be parting with it and my original Porsche Speedline wheels might be on the market soon. Thanks.

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When you had the block bore scoped, did they check it through the spark plug hole or up through the sump with the piston at TDC. I'm guessing the lifters got done because you had a ticking noise? Since the passenger side tip is getting sooty and it's always bank 2 that scores first, you probably have a scored bore.

What am I missing here, per the thread Bill linked above, Flat6 was saying this issue is most often attributed to tired fuel injectors. You pulled the motor, dropped $10k and didn�t change them? Not trying to sound smug, just confused.

I did not read the section on injectors until today and I had the service completed a while ago. Iogged on today for to give future buyers my story. Lastly, two shops prior, who solely worked on Porsches deemed it as �normal�. It has been a journey of unfortunate events with a clear lack of knowledge for these cars, on my part. I�ll update the post after I speak to my mechanic. Thank you all for chiming in.

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Hi!! Any news with this issue?? BR

My �99 996 did suffer from bore scoring on bank one and shortly after bank two. A rebuild was more than the car�s worth and thus, I sold it. Separate shops attributed the problem to poor casting (at the factory) and bad cooling system. While the 996.2 cooled the heads better it has the infamous IMS issue. I stayed away from the 996. I replaced it with a 987.1 2.7L which later suffered from a leaking intake valve and a spun bearing with 30k miles. Luckily a new engine was replaced under warranty. The insurance ended up paying $25k for a new long block on a Cayman I paid $18,000 for. I have since returned back to Mustangs and Corvettes as they are much faster, reliable and low maintenance. I just can�t fathom the high cost of owning a Porsche. Best! 🤝

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This is why I tell anyone that is interested in a 996.1/.2 or 997.1 n/a car to save their money and get a turbo. The M96/97 motors are time bombs.

Every car has its own maladies I think the 996 has no more or less then many other cars it all depends on previous ownerships upkeep and every day I drive my car it’s gets warmed up good and reved to redline every time

Never forget. Straight from Porsche. The source of so many problems we all get to deal with ~20 years later

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Thank you for you reply! My car has this issue and I have change injectors,O2 sensor, air mass sensor, spark plugs... and still facing the issue. I don't really know if borescoring is a consecuence of running rich or black exhaust is a bore scoring sympthon...

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Don�t waste your money and get a bore scope. I did all that in the hopes that it was something minor but in the end I knew it was the engine block.

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I purchased my �99 996 with 50,000 original miles. It was a one owner car with a good service history. It was a local trade in at Porsche of Monterey. My Cayman had 34,000 miles and was also a one owner car. The Cayman was mint! . The M96/M97 have a poor cooling system and warming it up or revving will do little compensate for that design flaw that eventually lead to its failure. I had the low/high �fan hack� and lower thermostat on my 996. Imagine, ghetto rigging what once was, a $60,000 sport car. Haha! I agree that most automobiles have some issues, but this is different. The M96 and M97 had designs flaws from the factory and should have been recalled. Look at the Cayenne of the time, it too suffers from bore scoring. Recalling or admitting the issue would have destroyed the already, nearly bankrupt Porsche company. I have been around Mustangs and Corvettes (and Lexus) all my life and I can tell you that they DO NOT have catastrophic engine failure! I wanted a Porsche since I was a child and when I had the opportunity, I jumped, twice. My first Lexus got an easy 200,000 mile on the same block before I sold it. My current Lexus is approaching 200k. Air-cooled Porsche can easily do that. I am not here to bash Porsche, as it has a wonderful history and a timeless design but as stated earlier, the 1999-2008 cars come with a heavy price tag! After two low mile cars with engine failures, I will stay away. Signing off�

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I wouldnt jump to any conclusions. Tell us about your car. How long have you owned it? Year, mileage? Have you done any oil testing on the car?

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I have last 13.000km (8000 milles aprox?), but I noticed the rear bumper was with soot 5000km ago (aprox). The car runs good, with no sound (aparently).I think oil consumption is a quart per mille, mnore or less. The long term O2 sensor is 3.5% for bank1 and 2.7% for bank 2. I have installed low termosthat. I think next step is to remove the exhaust and check if there is any leak befeore O2 sensor, check catalytic converter...I am completed stock with this issue but am thinking about @time4a911 advice: don't spend more money XD

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What year is it and how many miles is on the engine in total? The engine could be fine but you won't know until you dig in. Absolutely do all the inexpensive stuff first. If you are worried about borescoring, consider testing the oil which is a cheap exercise, drop the sump to see what you have in the pan and check your oil filter as well. If you really want to know, you gotta scope the bores from the sump.

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First of all, thank you for your time and sorry for my english, is not my native languaje . The car is a 996.1 '99, 93.000km on the odometer (60.000 milles aprox). Bank 1 sooty tail pipe and bumper is the main (and only) symphtom. I have changed: - All injector - All spark plugs with the coils. - Both O2 sensors - Air mass flow meter The long term O2 sensor is 3.5% and 2.7% on bank 1 and 2. The old spark plugs look quite similar, also the O2 sensor: It is tricky to say that one of them is more sooty than other... I have done compression test and the lowest value was 11.7 (cyl2), others are above 12. The filter was OK with no debris nor fiber nor aluminium nor steel. I have checked the wiring haness and I had to repair O2 sensor wires on bank 2 because it was damaged (no readings neither CEL, 35ohms on the signal wire vs 1ohm). Wires for injectors and coils looks OK. I was thinking to get a OBD2 PIWIS for get the injector miliseconds.... Meanwhile, my idea is to remove the exhaust system and look what I found. Regarding the oil analysis, is a good idea, I will do in the next maintenace! Thank you, again, for your support!

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Not alot of miles. Check on Yutube for the Rennvision videos on borescoring. No reason to loose sleep. Plenty of things you can do to keep the engine running if you have it and Plenty of things you can do to prevent it if you don't. One of which is change the oil 2x a year to keep it fresh. The other is to make sure you give it healthy exercise thru the rev range. Good luck and keep us posted.

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I Will check those videos BR from Spain!

What part of Spain ?

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South of Spain

Today, I have unplugged the oxygen sensor on bank 1 and reset de DME...I want to see what happen. But is curious, because the CEL light doesn't switch on on the dashboard.... I Will keep you in touch!

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OK I usually spend my summers just outside of Pamplona in Eugui. Viva San Fermin (running of the bulls)

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Hello everybody, after 550km in 40km daily trips (340 miles, aprox) it looks better. I cleaned the tailpipe and take a picture every day, and it looks a little bit darker after this distance,but this can come from the remains that are on the catalytic converter. I will keep watching, but it looks a leakage on the exhaust manifold (before o2 sensor) or any issue with the wires. Thanks!!

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Really nice place! If you need any help once will be on Spain, contact me

Do a smoke test on intake and exhaust to see if (and where) you have a vacuum leak. You Tube A leakdown test on a warm engine gives you further insight on condition of valves and rings. You Tube Oil consumption is about a litre per 1000km, right? Perhaps your piston rings are not able to move freely in their grooves (previous owner never using the engine's full potential). A fuel additive might help free them up. And as others already mentioned: scope the cilinders from the bottom via the sump or alternatively through the wrist-pin access port You Tube

Piruleta - Have you smoke checked for vacuum leaks? Both of your long term fuel trims are high. I suspect that on start your car is also running pretty rich until your cats and sensors heat up and the O2 sensors are happy enough to pull some fuel. This may be a vacuum issue. You may have cylinders that were washed down with fuel that possibly caused some scoring. The 2 things you need to do are scope from bottom and smoke test intake and exhaust side. 4 hours of labor for the scope, plus an oil change. I completely agree a used oil analysis program is very important for your engine and your sanity.

Thank you all for your advices I will do ASAP, BR!

Hi! I come back again...since I was father I havn't got time Relevant info: - SparkPlugs: 7000km - Oil: 4000km - More soot on the rear bumper/exhaust if I go hard - Oil consumption go hard is 0.5/4000km I have checedk the spark plugs and the color and compression test results are...: - Cyl1: perfect (11.7bar) - Cyl2: medium dark? (12,1 bar) - Cyl3: slighty dark (12,5 bar) - Cyl4: not checked (12,2 bar) - Cyl5: perfect (11,8 bar) - Cyl6: perfect (11,8 bar) I have drain the oil (I will send to analysis) and remove the oil pan, what do you think?? I have found and O-ring on the oil sump (do you know where it is???), brown debris (I think from the chain guide) and very small (2-3mm) alu semicircle. This week I will scope the bottom cylinders with the camera... Thoughts??? I start to think is not bore score...We will see...but I think is related with some electrical wires...I have had to fix some of them because there was some mouse in the car :S Thanks in advanced aluminium?? Semicircle Where the o-ring was The o-ring

Not sure what is the O-ring you are talking about, bot that piece you marked with the circle looks like a part of a timing chain roller. don�t ask me how I know.