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Can't say if the 997.1 port injection engine and the 991 DFI motors are that similar, but maybe the variocam stuff is similar enough. I don't think the variocam actuators.will effect fuel trims if that's your primary symptom. Sounds like you have a vacuum leak on that bank.
Check your bank 1 and bank 2 camshaft deviations too. Variability there is more likely the variocam solenoids.
Yea. I did a smoke and pressure test from the air box to intakes. All good there. Bank 2 cam actual does vary some from target. bank 1 is more stable. Trims wise, it may be weak injector also. So have to tell at this point.
FWIW this is very similar to my issue with my 9A1 DFI engine.
Rough at idle sometimes and symptoms like misfire were all on one bank and never on the other.
Changing the solenoid (I think the cam lift) fixed all the issues so far.
My hypothesis is that when it's not working right the engine assumes that when switch is flipped, the cam profiles will change and thus the fuel mapping should be adjusted for that.
Well if the solenoid doesn't do that correctly (or at least not consistently), the engine is going to send the extra fuel anyway, and the mixture ends up being rich.
Thats the other code I was getting at the O2 on bank 2.
But I am not sure that explains why its rough at idle as I have not found anything talking about when the cam timing and cam lift changes are going to be enabled.
It would be interesting to know roughly how often the engine is designed to change the cam timing or lift. Is it every 100 rpm?, 1000? That would make it clearer what might be happening at idle to make it rougher than normal
FWIW this is very similar to my issue with my 9A1 DFI engine.
Rough at idle sometimes and symptoms like misfire were all on one bank and never on the other.
Changing the solenoid (I think the cam lift) fixed all the issues so far.
My hypothesis is that when it's not working right the engine assumes that when switch is flipped, the cam profiles will change and thus the fuel mapping should be adjusted for that.
Well if the solenoid doesn't do that correctly (or at least not consistently), the engine is going to send the extra fuel anyway, and the mixture ends up being rich.
Thats the other code I was getting at the O2 on bank 2.
But I am not sure that explains why its rough at idle as I have not found anything talking about when the cam timing and cam lift changes are going to be enabled.
It would be interesting to know roughly how often the engine is designed to change the cam timing or lift. Is it every 100 rpm?, 1000? That would make it clearer what might be happening at idle to make it rougher than normal
Good points. The issue I'm having is that w independents don't seem to know these answers. I have a good relationship with my local dealer, but even though that's symptoms started be for my mods and the dealer understands that, my warranty company likely won't agree. My main hesitation to taking it to the dealership is that my independent looked what we think is a book time for changing the lift solenoid and it came back with 18 hours R&R engine removal and cam locking. At $225 hr, I'm looking at a 5k bill if the warranty denies it. I'd rather do it my self and buy the tools.
I have been on a different thread and have been told that neither cam solenoid requires the cams to be locked to replace the solenoids. I really am conflicted as to attempt to change them without locking the cams. If I'm wrong, bingo! Totaled motor.
What did you get changed labor hours to replace the solenoids? Do you have a part number to verify which one they changed?
Thanks again for the help. I prefer to work on my own stuff, but I'm finding that getting even the simple stuff like a real workshop manual for these cars is difficult.
I replaced the solenoid myself. On the 9A1 (and maybe the M97 too) the solenoids I was replacing were right between the coil packs. If you can replace the spark plugs and you have a E8 Torx socket it's pretty easy to do yourself. MIght
That said, I did this by removing the bumper, heat shields and side mufflers using a quickjack. With a lift and experience you might be able to do it just removing the side muffler alone to get access to the coil packs. But doing all that on my back would be a pain and my body is too creaky for that noise. That might be where the time comes from? No idea how shops account for their time.
I replaced the solenoid myself. On the 9A1 (and maybe the M97 too) the solenoids I was replacing were right between the coil packs. If you can replace the spark plugs and you have a E8 Torx socket it's pretty easy to do yourself. MIght
That said, I did this by removing the bumper, heat shields and side mufflers using a quickjack. With a lift and experience you might be able to do it just removing the side muffler alone to get access to the coil packs. But doing all that on my back would be a pain and my body is too creaky for that noise. That might be where the time comes from? No idea how shops account for their time.
I understand the part number 9A110530803 refers to both solenoids (Bank 1 and 2) right?
Is it also suitable for 9A1 x51 997.2 engines?
I have no fault code but the idle is unstable..
I replaced coils and spark plugs and still unstable (there are slight movements of the needle in the idle)..
Therefore, I am considering replacing the two solenoids after everything I have read on the subject.
If there is a fault or misfire (God forbid) is this something that can be seen by scanning fault codes in the iCarsoft POR v2.0 device?
On the other hand, I read a lot that an unstable idle is a common and normal thing in 997.2 so I'm really confused.
I have already posted this about these actuators... but to repeat my opinion.... I replaced these actuators, located on each bank between the spark plugs, to no effect. When these fail or hiccup, they throw a code. Having incorrect valve lift at the wrong time is a big failure and will throw a code. I suspect yours have not failed. Further, I don't think they are related to a stumbling idle. Stumbling idle has been a common issue with our .2 engines and has been mitigated by first, thoroughly cleaning the throttle body with a cleaner... I used MAF cleaner..., and then replacing the throttle body. I did all of the above... replaced the actuators, cleaned the MAF sensor, cleaned the throttle body a few times (did help the stumble but then stopped working), and then replaced the throttle body. Replacing the throttle body finally knocked out my uneven idle. IMO, you would be better served replacing the throttle body and its gasket (gasket is sold separately). Replacement is really easy and you can buy the exact Bosch part cheaper than buying a Porsche part (as I did).
To obtain the correct part number, download the latest parts catalog directly from the Porsche website. I have found that using .1 part numbers is a mistake. While the advice you get here is fabulous, I always do my own homework using the latest Porsche parts catalog specific for .2 cars before I order anything. The .2 engine is a different engine. The engine management computer is different. Even suspension parts differ very subtly between models even though they look the exact same.
Good luck and report back.
Peace
Bruce in Philly (now Atlanta)
Last edited by Bruce In Philly; 03-13-2022 at 09:33 AM.
I have already posted this about these actuators... but to repeat my opinion.... I replaced these actuators, located on each bank between the spark plugs, to no effect. When these fail or hiccup, they throw a code. Having incorrect valve lift at the wrong time is a big failure and will throw a code. I suspect yours have not failed. Further, I don't think they are related to a stumbling idle. Stumbling idle has been a common issue with our .2 engines and has been mitigated by first, thoroughly cleaning the throttle body with a cleaner... I used MAF cleaner..., and then replacing the throttle body. I did all of the above... replaced the actuators, cleaned the MAF sensor, cleaned the throttle body a few times (did help the stumble but then stopped working), and then replaced the throttle body. Replacing the throttle body finally knocked out my uneven idle. IMO, you would be better served replacing the throttle body and its gasket (gasket is sold separately). Replacement is really easy and you can buy the exact Bosch part cheaper than buying a Porsche part (as I did).
To obtain the correct part number, download the latest parts catalog directly from the Porsche website. I have found that using .1 part numbers is a mistake. While the advice you get here is fabulous, I always do my own homework using the latest Porsche parts catalog specific for .2 cars before I order anything. The .2 engine is a different engine. The engine management computer is different. Even suspension parts differ very subtly between models even though they look the exact same.
Good luck and report back.
Peace
Bruce in Philly (now Atlanta)
Thanks Bruce!
Honestly, I forgot to update that I also replaced the throttle body and all the vacuum tubes (3 threaded plastic pipes) and it really helped a lot. Strange noises disappeared from the throttle body and most of the hesitation disappeared.
At the same time, there is still a slight hesitation in idle (scan attached). The RPM needle is not completely stable. In addition there is a "pak" noise that comes intermittently from the throttle house area (apparently it is also related to MAF rich or poor fuel or additional vacuum leak or it is a normal noise of our engines..).
I have already posted this about these actuators... When these fail or hiccup, they throw a code. Having incorrect valve lift at the wrong time is a big failure and will throw a code. I suspect yours have not failed. Further, I don't think they are related to a stumbling idle. Stumbling idle has been a common issue with our .2 engines and has been mitigated by first, thoroughly cleaning the throttle body with a cleaner... I used MAF cleaner...,
Good luck and report back.
Peace
Bruce in Philly (now Atlanta)
I agree 100%. When your vvs fails,sticks your idle is like that of a dragster about to stall and you will be throwing codes.
I agree 100%. When your vvs fails,sticks your idle is like that of a dragster about to stall and you will be throwing codes.
I understand .. so this is not my situation🙏🏼.
But it is always good to learn something new..
If so, it's probably MAF and everything around it ..
I heard that MAF does not always throw codes, is that right?
If the computer reads out-of-bounds values from the MAF, it will throw a code. There is alot of mystery about the MAF... I have read it is blamed for all kinds of problems. Real? I am at the limits of my experience here. My buddy at Ford likes to tell me that these modern engines are so finely tuned that if a car so much as farts, they throw codes. However, problems can present themselves without codes thrown and a stumbling idle is one of them.
If the computer reads out-of-bounds values from the MAF, it will throw a code. There is alot of mystery about the MAF... I have read it is blamed for all kinds of problems. Real? I am at the limits of my experience here. My buddy at Ford likes to tell me that these modern engines are so finely tuned that if a car so much as farts, they throw codes. However, problems can present themselves without codes thrown and a stumbling idle is one of them.
Peace
Bruce in Philly
That being said, ״There Is More To It Than Meets The Eye״.
My Porsche mechanic says that everything is fine and this is normal behavior of 997.2 but as you say, the MAF can cause a lot of trouble like dirt in a throttle that does not throw codes ..
So I think I will start and finish with the MAF, because if there was a code we would see it.
As a recap I had idle issues starting with an occasional high idle condition that would stop after the car cooled. The idle then started to stumble from time to time. Lately the idle will get into a stumble condition that drops under 500 RPM then resets to normal for a few seconds. Then cycle starts again. The car will idle fine for a while after cold start then gets worse as the cars heats up.
Diagnostic findings.
Short term fuel trims are stable on bank 1. Bank 2 will begin to richen as the idle becomes more unstable. Lambda on bank 1 is stable at stolic 14.7 bank 2 Lamba will lean out as STFT bank 2 richens. Cam angle on bank 1 remains stable at target of 124.9. Bank 2 cam angle wlll rise as the idle degrades several degrees until the stumble happens.
Solutions to fix so far.
Remove custom tune and return to stock. No change.
Replace plugs and coils. No change
Rreplace 02 sensors no change
Swap cam sensors banks 1&2 no change issue did not follow bank 2 cam sensor.
Replace cam sensors. No change
Swap 02 sensors no change( new 02 sensors just did this to rule out bad DOA 02)
Replace throttle body. No change
I Have 6 new injectors and 2 new VVS solenoids to try next.
Weird side note. I did try a bottle of liquid molly Dijection cleaner yesterday on a whim. All day yesterday my STFT's were way more stable and NO stumbling. Now our temps did drop 45 degrees yesterday and I haven't driven it today. That may be a factor. It could be a total fluke. I am going to fill up now and add another bottle.
If this improvement continues I will go back to clogged injector. If that's the case I'll replace them and see what happens.
I have tried to engage 2 independents since doing the above work and neither was willing to take on any additional diagnostics. My dealer who I have a great relationship with has no input which I understand since they haven't inspected the car (I haven't taken to them because if they dive into it and engage my warranty and it gets denied, I could easily be looking at a 5-8k bill).
So I'm left with many questions. I will update if the DI injector cleaner continues to help. Also once I replace the VVS solenoids first then maybe ultimately all 6 injectors.
Thanks again for all the insight everyone.
Last edited by Ducaiti999; 03-13-2022 at 01:09 PM.
You raised an interesting point, which may be related to a fuel line, I know that Porsche markets additives, but in 997 it is explicitly stated in a car book that Porsche does not recommend using fuel additives (and oil).
I wonder if the reference is to fuel additives that Porsche is not willing to take responsibility for (that do not have a Porsche stamp) or can 997 be used in original Porsche fuel additives 00004320902?
You raised an interesting point, which may be related to a fuel line, I know that Porsche markets additives, but in 997 it is explicitly stated in a car book that Porsche does not recommend using fuel additives (and oil).
I wonder if the reference is to fuel additives that Porsche is not willing to take responsibility for (that do not have a Porsche stamp) or can 997 be used in original Porsche fuel additives 00004320902?
Interesting. Never considered Porsche didn't recommend additives. In my case I've never used them until now. My tuner was suspecting fuel injector for a while, but I just didn't think it was them due to lack of fuel related codes. Now I wonder. I'll go ahead and replace them and see.
For me I will replace a part over a rebuild for this car. At the power levels I'm at and shooting for, I can't afford any type of issue, especially with fueling.
I just got to my shop and so far no stumble. Over the last week or so by the time I got here it would be stumbling bad. It's still cool here (72 not 90). I can't rule out a temp issue having an affect but tomorrow will be warmer. We will see.
03-11-2022, 01:23 AM
