Rough Idle Stall since Rain

[Björn Östen Miles]

Ok,

 

So since it rained heavy, my car has started to idle rough and seems to dip revs to say 300 and then go back to good resting idle.

 

I suspected a faulty MAF but have replaced it with new Bosch and still remains.

 

The other disturbing thing is the fuel trim (short) is at -23% which is large correction I think.

 

The only thing I think is suspect vacuum leak.

 

I can post video demonstrating the symptoms if that may help.

 

Björn (Nalle)

[Ahsai]

Have you checked the coils?

[Björn Östen Miles]

Apologies

 

Yes new coils and plugs, I would assume the obvious.

 

I was thinking to get a smoke test maybe, had new filters.

 

CEL is on, but random misfires on bank 4, 5 and 6 is the only codes, which led me to think it is the o2 sensor on that side.

 

At high revs it is fine, ran a fuel detergent for injectors and also cleaned throttle bodies etc.

 

Had service done not long ago, new filters etc and oil change as well.

 

Thank you

[Loren]

:welcome: 

 

O2 sensors do not cause misfires -they report them.

You need to post your fault codes here or everything is just guessing.

[Björn Östen Miles]

P0300, P0304, P0305, P0306

 

This is it!

 

Which I understand is Random misfire, misfire cylinder 4, 5 and 6 

 

My understanding is that a faulty o2 sensor can cause an misfire due to the mix (I think this is how you say it) is adjusted by the data provided by the o2 sensor which can cause failure of ignition for the reason of oxygen imbalance. 

 

Or am I misunderstood.

 

Björn

[Ahsai]

Some questions:

- Do you have access to Durametric? Will be good to check for any pending/Porsche-specific codes. Also good to check for vitals like cam deviations, misfires in real-time, MAF, fuel trims, O2 sensor readings, etc.

- The short term fuel trim -23% was on which bank? What are the short term and long term fuel trims on each banks?

- Have you checked if the coil connectors are engaged properly (clicked when installed)?

- If you remove the oil filler cap, do you feel some suction or no suction?

[Ahsai]

- Also, do the symptoms show up only when the engine is wet?

[Björn Östen Miles]

Hei Ashai,

 

No, it does not only correlate to the rain anymore, it is just when it started.

 

I checked for the vacuum on the oil inlet, there is a lot suction on the pipe.

 

I will get you the reading on the trim later, the 23% was on the short term, and it was on the same bank as the cylinders 4, 5 and 6, which diagnostically led me to think of the o2 sensors.

 

Kitos

 

Bjorn

[Rikky]

Terve Bjorn,

 

If there is a lot of suction on the oil filler cap; sounds like an AOS problem. If your AOS is not working properly you will note that it is difficult to remove the oil filler cap - and usually there is a lot of white exhaust smoke too, not always.

AOS is not that expensive to replace if you do it yourself.

[Ahsai]

AOS failure is a possibility and the way to verify is to measure the crankcase vacuum using a manometer (either home made with clear rubber tubes filled with oil or a digital one for ~$US40). It should read ~5 inches of water.

 

The other thing you can try is to swap the precat O2 sensors between banks if you still suspect the sensor. If you have an air leak, your short term fuel trim should be positive and not negative though.

 

You can also check if the variocam+ solenoids (mounted on the cam cover) to see if their brackets are loose or the seals are leaking. Air leak through the seals can cause misfires.

 

Without Durametric or Porsche scanner, you're under-equipped to deal with these codes. Misfires on a single bank could be lifters, variocam+, air leak, etc.

[JuncoJones]

Without Durametric or Porsche scanner, you're under-equipped to deal with these codes. Misfires on a single bank could be lifters, variocam+, air leak, etc.

 

 

Agree with Ahsai, +1 for Durametric.

[Björn Östen Miles]

Kiitos Hyvää Ricky

 

The reason for o2 sensor thinking was that it occurred when it was wet, and maybe symptom of short.

 

I am not sure how to get to the VC solenoid, is there a rubber seal that connection with the Cam Cover?

 

I know where the cam covers are either side, I can see the coil packs mounted to them.

 

For the purpose of investigation, the general driving symptoms of the car are revs dipping when the engine revs of 3.5k and sometimes the revs drop to 500 and the engine is struggle.

 

PIWIS data is just the random misfire on the 4,5 and 6 cylinder, nothing pending or recorded other than this. 

 

A year ago there was a CEL for the cam position sensor, but never happen after.

 

Näkemiin

 

Björn

[Ahsai]

Photo of the solenoids in post #17 here

http://rennlist.com/forums/996-forum/894568-replace-chain-adjusters-and-solenoid-attached-to-tensioner-2.html

What are the cam deviations on both banks and are they rock steady throughout the rev range?

Can you monitor the O2 sensors' voltage reading with your scanner?

[Björn Östen Miles]

Yes it is possible for me to do that and freeze frame as well.

 

I will observe, when I did look at this before, it was one o2 sensor that was very up and down and performing like the other. 

 

Bjorn 

[Rikky]

Hi Bjorn,

 

Did you measure the vacuum on your crankcase? If it is really hard to remove, no need to measure as that is exessive vacuum already - AOS replacing is not that expensive if done yourself. I would solve that first and take it from there.

Good luck.

[jglaze]

What year is the car? I've read on a number of other forums about the potential for bad valve lifters on some '05 cars, which demonstrate similar symptoms you describe (cold start, random misfire). It seems like its a fairly rare issue, but common enough for Porsche to issue a technical bulletin.

 

I'm particularly interested because I just passed on the purchase of an '05 S that developed a random misfire under exactly the same circumstance as you (cold/wet).

 

Good luck!

[Björn Östen Miles]

Hey Guys,

 

New code today, P1090, and the idle is getting worse.

 

Would it be helpful to post a video of the symptom.

 

Reading this leads me to maybe three things, what do you think?

 

a) Throttle Body or Sensor not good

b) Lift solenoid problem

c) Sticking lifter

 

I have cleaned Throttle body, changed MAF so I am just not sure now.

 

Bjorn 

[Björn Östen Miles]

Also, when running is rough I turn off and on and all better until I hit over 3.5 to 4k revs.

 

Also it seems the rev dip and then there is a click and it returns to ok again.

[Ahsai]

What if you drive your car with the MAF unplugged?

[Ahsai]

Some relevant threads

 

http://www.renntech.org/forums/topic/43099-2005-997-c2-engine-trouble/

 

http://rennlist.com/forums/997-forum/757105-rough-idle-but-no-faults-present.html#post10492990

[Rikky]

Bjorn,

 

P1090 is a MAF sensor fault detected. Not necessarily the MAF itself as a dirty throttle body can result in the same trouble code.

 

Check your MAF connection first.

Check your throttle body, mabe it is very dirty (happens more when you use a sports airfilter).

 

My guess is that your MAF and throttlebody is creating the problem as your AOS is faulty. If you have an excessive vacuum, you told us it was difficult to remove the oil filler cap - than lots of crankcase vapours, too much, end up in your intake system and poluting your MAF sensor and throtlle body. I have seen throttle bodies full of oil and carbon too..

Just take the air filter box out and look at your throttle body if it is very dirty.

[JuncoJones]

Hey Guys,

 

New code today, P1090, and the idle is getting worse.

 

Would it be helpful to post a video of the symptom.

 

Reading this leads me to maybe three things, what do you think?

 

a) Throttle Body or Sensor not good

B) Lift solenoid problem

c) Sticking lifter

 

I have cleaned Throttle body, changed MAF so I am just not sure now.

 

Bjorn 

 

 

Bjorn,

 

Posting a video always helps, it provides us with more information. So if you can, go ahead.

 

 

Now In my typical style, I’ll throw some unconventional techniques that I would try (and already have, of course) in my own car:

1. Liqui Moly Engine flush – some people don’t like this product, I find it extremely efficient. It will thoroughly clean your engine from inside. These engines are highly dependent on effective oil pressure, and can potentially help eliminate oil-related issues, like sticky lifters and clogged solenoids. This will clean any gunk and build-ups, but of course, it won’t magically fix damaged or worn-out components. Add it to the oil, idle the car for 10 minutes and replace oil and filter.
2. Liqui Moly Injector cleaner – this is a fantastic product. Add it to your fuel with a full tank of gas. The first time I used it on both my cars, I remember I felt a huge improvement after the first 10 minutes of driving. Once the injectors are clean, you won’t feel any noticeable difference.

 

Now, these won't necessary fix your P1090 code, but like I mentioned above, can help rule out other possible causes.

Edited November 26, 2015 by JuncoJones

[Björn Östen Miles]

Guys SOLVED!

 

Actuator Valve 99710530100 Was the problem!

 

It took me about 2.5hrs to take the rear fender off, heat shield and rear silence, exchange of the valve and then remake the car.

 

Turned the key and zoom zoom it was perfected!

 

If people would like help then this is more the likely their problem.

 

It cost around 105 euro for the part and it cost me much more in problem!

 

Thank you all for help especial Ahsai as it was that which helped above.

 

Kiitos 

 

Björn (Nalle) 

[Ahsai]

Well done!

[Rikky]

Good news!