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tristancboyd@gmail.com

Lopey Idle and intake pops on a cold start

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The P0102 means MAF no/low signal, shorted to ground, etc. I would check the MAF electrical connection and continuity of the wires between the MAF and the DME.

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The P0102 means MAF no/low signal, shorted to ground, etc. I would check the MAF electrical connection and continuity of the wires between the MAF and the DME.

I will add this to my ever growing list.  I'll likely crack this thing open to start everything on Saturday morning.  I still love my car though.

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Here's a 6 minute video of a cold start with the manometer reading.  It was either having a good day for starting or wasn't cold enough to cause the problem completely.  At the 5:25 mark, during a rev, you can hear the car pop, it sounded like a small backfire or intake pop, but that is a symptom and does it more often on the harder starts.

 

https://youtu.be/WK4wps8SeOI

Edited by tristancboyd@gmail.com

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That looks good me. I'm not sure if the slight vacuum fluctuation when you blipped the throttle is normal or not. Probably it is.

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That looks good me. I'm not sure if the slight vacuum fluctuation when you blipped the throttle is normal or not. Probably it is.

Ok.  Did y'all at some point say that oil inside the intake bridges (i forgot what they are called) could be another sign?  I'm in the process of removing the throttle body and its looking nasty in there from what I can see so far.  I'll post a picture in a few once I get it all of the way out.

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A light coat of oil is normal. It's hard to tell from the photos. They don't look too bad to me though.

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A light coat of oil is normal. It's hard to tell from the photos. They don't look too bad to me though.

The picture on the ride side, middle shows a small puddle I guess you could say.  There is about the same amount sitting in the flange like area exiting the AOS for where it connects behind the throttle body.  Should I go ahead and change it since I have a new OEM one here?

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From your vacuum signal video, there does not appear to be excessive vacuum inside the engine cases.  There will always be some oil residue inside the intake system, that is just a fact of life with these engines and this AOS.

 

I would change the AOS simply because (1) You already have it, and (2) Porsche has improved the internal components, so your new one should be better made. 

 

A couple of caveats: Remove the small "J" tube that runs from the top of the AOS to the intake, and carefully examine it for any signs of cracks, etc.; we have seen these fail way too often.  Secondly, I would also have good look at the long hose that runs from the lower AOS connection under the intake runners and over to the PCV unit for the same reason you would be looking at the short hose.  Problem with this long hose is that you need to disconnect it at the PVC and tie a thin but strong cord to it before extracting the hose from the AOS end.  By doing this, you will have the cord to snake either the existing hose (if it is good) or a replacement back into place after checking it. 

  • Upvote 1

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Ok guys, I'm really needing some help.  Initially I thought it was running better but I was dead wrong.  It sounds better driving and any accelleration over 2k rpm but take off have become a night mare and have only gotten worse as the day went on.  It got to the point where I didn't feel safe driving it in town because I was stalling out multiple times at lights.  I got a CEL once today, a P1117 but i read it was an o2 sensor deal.  I checked my readouts and all four were reading around .07 so i cleared the code and nothing has come back.  

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Are you sure the plenum connections are air-tight. Those hose clams can be tricky. Perhaps retrace what you have removed and reinstalled and make sure all the connections (electrical connectors as well) are tight?

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Are you sure the plenum connections are air-tight. Those hose clams can be tricky. Perhaps retrace what you have removed and reinstalled and make sure all the connections (electrical connectors as well) are tight?

I took extra time with those to make sure I got them on right.  When I put everything back together, I sprayed everything (carefully) with carb cleaner to see if I had any vacuum leaks.  I double checked the connectors as well.  It is possible I missed something but I won't get to crack into until after work tomorrow.

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I tried that but I'm not sure if I got the sequence or timing right.  I have a few videos to link too.  The idle was surging between 5-700 RPMS and the lights would dim with the drops.  I have video of it too.  I'll have it up in a few minutes

Edited by tristancboyd@gmail.com

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Concerning your last video "Surging idle", the parking brake must be engaged for a proper measurement when the wheels are off the ground, otherwise the transmission and the wheels are a little dragged by the engine, causing a slight difference in RPM at idle due to no torque. 

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Concerning your last video "Surging idle", the parking brake must be engaged for a proper measurement when the wheels are off the ground, otherwise the transmission and the wheels are a little dragged by the engine, causing a slight difference in RPM at idle due to no torque. 

This was with the car in neutral. clutch in or out didn't change it.

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I checked your log. The problem is intermittent. When it occurs, the MAF read very high even at idle speed. It was 7g/s (i.e., 25.2kg/hr) or higher. The fuel trim pegs out at -25% (short term fuel trim) so the engine was running rich. All O2 sensors have high sustained (0.7v) voltage (too rich). Is the MAF a Bosch unit?

 

Also, when this condition happened, the throttle position always read 2.35239% fixed. That looks odd. Also, LTFT values are always fixed so not sure how much we can trust the Torque log values. 

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BTW, one possibility is a sticky evap purge valve (that feeds into the throttle body). It can create a too lean or too rich condition, depending on how rich or lean the fuel vapor is at the time in the gas tank.

Edited by Ahsai

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I checked your log. The problem is intermittent. When it occurs, the MAF read very high even at idle speed. It was 7g/s (i.e., 25.2kg/hr) or higher. The fuel trim pegs out at -25% (short term fuel trim) so the engine was running rich. All O2 sensors have high sustained (0.7v) voltage (too rich). Is the MAF a Bosch unit?

 

Also, when this condition happened, the throttle position always read 2.35239% fixed. That looks odd. Also, LTFT values are always fixed so not sure how much we can trust the Torque log values. 

It is not a Bosch.  Should I unplug it and take it for a drive and see what readings change with it?

 

BTW, one possibility is a sticky evap purge valve (that feeds into the throttle body). It can create a too lean or too rich condition, depending on how rich or lean the fuel vapor is at the time in the gas tank.

I'll try to find some information on this and see if there is a way to clean it up.

 

 

Someone on another forum thinks its the Variocam stuff.... from what I've read, I really hope not.

Edited by tristancboyd@gmail.com

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