When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
This has been driving me nuts for a while. It's hunting at start up idle between 900 down to 700 rpms bouncing up and down slowly. So, I cleaned the throttle body thoroughly. Reattached the boot and there are no air leaks as I made sure it fit perfectly and tightened down the bands tight. I also removed and cleaned the MAF sensor with MAF sensor cleaner. And it's still hunting. I purchased a new MAF sensor made by Bremi for my 2009 Carerra 4S the correct part number. I have not installed it yet but lets assume it doesn't change the idle hunting.....what would still be causing it to hunt other than a vacuum leak which I don't think it has. I've read the the throttle body may need to be replaced. Other than that I have no idea unless it's a miss fire on one of the cylinders or a HPFP. BTW it is NOT throwing a code at all. I don't have a acceptable file type to upload although I did a compressed video file but can't upload it.
Where do you live? Is it not cold enough in the morning on the first start where the initial idle should be in the enrichment mode up over 1,000 RPM or does the .2 DFI motor not follow the same protocol as the .1?
If it's supposed to, I'm thinking the MAF is your problem as it might not be getting the correct air temperature information. Does the hunting go away after a couple minutes?
when i start my car, first 20-30 seconds steady high rpms, then it does the same dance 3 times dropping between 700 and 900 and then steady idle. car runs flawless and does it everytime after sitting overnight, but if the engine is warm or been driven in the last 8 hrs it doesnt do it. Im not worried about it, looks normal to me.
It's not exactly the throttle body, it's the idle air control which on these is integral to the throttle body for certain ones. The green arrow in this photo from Pelican Parts is pointing to the idle air control.
Later throttle bodies have an integrated idle air control which is non-replaceable. Here's what the 82mm throttle body looks like:
The IAC lives under the black housing there. Can't really replace it.
And yes, the symptoms line up exactly with a bad idle air control. Sometimes it's just grime in the air path, so cleaning it out is all the fix required when that's the case. But this is a part that will eventually fail in absolutely any car. Depends more on the environment, engine's diet, and typical driving conditions more than mileage. The more the motor has to cycle, the sooner it will fail.
Also note that a bad IAC shouldn't throw a misfire code. It may, but it's not expected to. Codes expected would generally be P050x, Idle Control System malfunctions. The only way you can really test these IACs is with the OE tool (PIWIS) though. It's the downside of technology. Used to be you just needed a 12v source and you could test the motor. Now it's all on the CANbus and usually PWM.
The 997.2 DFI motors do not appear to follow the same high idle behavior you'll see in other cars either. Would have to ask Porsche why that is - maybe for noise reasons? Either way, they drop out of high idle very quickly.
All things are possible! However, in my experience with other systems, I wouldn't expect it to resolve at operating temperature and would expect a pending code.
A narrowed/sticking IAC can often self-resolve at operating temperature because of thermal expansion and intake air temperature changes.
Talking about MAF on 997.2s... how should the rubber boot cover of the MAF wiring be attached? Loosely or inside the connector. The pic below shows what I typically see (loose).
I would say loose. That's a rub and/or flex point. If you tuck the boot in so that it can't move as easily, you increase the wear on the rubber, which can ultimately lead the boot tearing or breaking. Basically, that's a dust and rub boot, not weatherproofing. It's there to keep the leads (wires) from getting broken, not to provide a watertight seal.
All things are possible! However, in my experience with other systems, I wouldn't expect it to resolve at operating temperature and would expect a pending code.
A narrowed/sticking IAC can often self-resolve at operating temperature because of thermal expansion and intake air temperature changes.
It was in my case, although I was getting the CELs. It only ran rough at idle but was ok when some throttle was applied. Replaced the VarioCam actuators last night and it smoothed it out at idle and no more codes.
Well, my hunting idle needle on the tach, has been fixed! YES! For months I've watched and listened to my engine having a uneven idle. I did everything I could and that I learned here to fix it. Cleaned the throttle body, cleaned the MAF, replaced the MAF and nothing worked. So I decided to bring it to my local Porsche dealer. I told them what I did and being my local dealer has been around for a long time, and because I know them well having had them work on both my 997s (2007 and 2009) I felt they would be able to fix it. And so no codes were showing. Brought it there on Wednesday morning. No news Wednesday. Thursday no news till about 4 pm. They couldn't get the idle to jump around enough to call it a problem. Then on Friday, the mechanic apparently tried tapping and hitting on the throttle body and the idle started jumping all over. My Porsche needed a new throttle body and seal. Picked up the car today and the idle and tach needle is rock solid steady with no quiver or movement at all. Finally after months the engine runs perfectly. They did an overall 30 pt vehicle inspection and got all green checks OK. Went home cleaned the wheels, polished it, cleaned the interior with Zaino's leather cleaner, and Zaino's Grand Finale and she is sparkling like new and purring like a kitten. Kudo's to Porsche of Monmouth and their fine staff.
Before I saw your last post I was going to tell you to replace the TB. I have a 2010 C4S Cab 997.2 and had the same problem last year. Except if you don't fix it the problem morphs into surging while driving. I have a very long thread on this forum from last year running thru the details. The failure point came when it threw a code and my car shut down at 60 mph, surging itself into seizures. Then they were able to fix it. Once the new TB was installed, right at a year ago, it's been smooth as new. I just re-oiled the BMC filters yesterday, pulled the MAF and spray cleaned it off, my annual maintenance program underway.
Well, my hunting idle needle on the tach, has been fixed! YES! For months I've watched and listened to my engine having a uneven idle. I did everything I could and that I learned here to fix it. Cleaned the throttle body, cleaned the MAF, replaced the MAF and nothing worked. So I decided to bring it to my local Porsche dealer. I told them what I did and being my local dealer has been around for a long time, and because I know them well having had them work on both my 997s (2007 and 2009) I felt they would be able to fix it. And so no codes were showing. Brought it there on Wednesday morning. No news Wednesday. Thursday no news till about 4 pm. They couldn't get the idle to jump around enough to call it a problem. Then on Friday, the mechanic apparently tried tapping and hitting on the throttle body and the idle started jumping all over. My Porsche needed a new throttle body and seal. Picked up the car today and the idle and tach needle is rock solid steady with no quiver or movement at all. Finally after months the engine runs perfectly. They did an overall 30 pt vehicle inspection and got all green checks OK. Went home cleaned the wheels, polished it, cleaned the interior with Zaino's leather cleaner, and Zaino's Grand Finale and she is sparkling like new and purring like a kitten. Kudo's to Porsche of Monmouth and their fine staff.
You're the second one I see who had exactly the problem I probably have. I'm glad to hear it's solvable and not terrible. I have noise and my RPM is unstable in idle. I have GTS 2011 997.2 PDK. What is the exact part number that fits GTS? (Or 997.2 3.8 (if the same)) THX
09-06-2018, 11:40 PM
Hunting Idle
