Highpox1

Petza914- I read up on the Durametric.. up until now I've never had a reason to own it. The 'Enthusiast Kit' Option 1 may be a worthwhile investment. It's <$300, but can it record/log a multitude of data while driving, or is it LIVE DATA only, no log? In theory, I could plug it in w/ my laptop in the car and just drive if it's recording responses. That would be stored, and available for analysis later. That way I wouldn't have to drag along a mechanic for a 30 minute ride waiting for the problem to start. Am I missing something or is that how it works? Otherwise I'd need a man along to read live data while it was surging.

DC911S

You should be able to store data. There are other products that can store data too but not let you clear codes or change flags that are cheaper, which Durametric is for. If you have buds with porsches you can split the cost as you get three VINs with the enthusiast option.

Ducati_John

I had a somewhat similar thing happen on a motorcycle - it would surge at low throttle settings while cruising, but not at idle or higher throttle. Turned out to be a bad ground in the ECU. I saw it by data logging - the throttle position sensor signal was very noisy at low openings. So the ecu thought I was opening and closing the throttle very quickly. The ecu would then add more fuel and spark advance giving more torque, then take it away when the throttle signal dropped again causing it to buck back and forth. It was cycling at around 50ms iirc. I first swapped the TPS thinking that was bad, but it was fine. Checked the wiring - fine. Eventually the ECU died, I swapped that and it fixed it.

I'm not saying this is your issue, just that datalogging should be helpful in seeing what the inputs to the ecu are and give you something to test.

fwheelerjr

Same year, model, mileage, and daily driver. It would crank for 5 seconds or more before starting. A few starts where it would struggle to start and immediately die. A few times it went into limp mode (I forget the exact PCM message) while driving. A stop and restart would correct. Diagnosis: HPFP (lower left rear of engine). Big DIY and cranked like new; first hit of the starter since. HPFP is about $850 at the dealership (too expensive to trust otherwise).

Highpox1

Petza914- I ordered a Durametric. Looks like it would be good to have. I talked to their tech guy and he indicated it could log a multitude of components at once....more limited to the laptop capacity. After reviewing all the components that can be logged, there are only a dozen or so that would apply to my issue. Given the problem repeats, I could log several at a time over the course of a drive, and capture the culprit. Dumb question- how do you know what readings are off? I could log the same components when the air is warmer and the problem doesn't occur, then compare the two for variations. Other than that, I would need a guide to explain correct manifold pressure, for example, to determine if there was a vacuum leak, etc.

Petza914

Not a dumb question at all - a very valid one. As you suggest, I figured you could compare readings when it's happening and when it's not. You could also compare Bank 1 and Bank 2 fuel trims to see how close they are to each other, take MAF readings during a cold start and a warm start to see if there's a difference, etc.

I don't have a baseline for what are normal for the various viewable parameters, but someone like Macster or semicycler may.

millertimefl

I have same car and I had this issue a few years back. Do you have a non steady idle? My surge was everywhere at idle and while in gear driving. It took the dealership a week to find it ended up being the throttle body. There was play in the gears of the air flap in the TB so it would move and not give car steady flow of air. Strange issue but that was it.

Rod928

I have experienced the same problems with surging (2009 C2S PDK)... Tried to clean MAF, Replaced MAF, replaced Air Oil Separator... Until I saw some 996 owners describing the same symptoms linked to a dirty throtle position sensor potentiometer... I decided to skip the step of cleaning it and instead ordered a new throtle body that took care of all my problems

Highpox1

Yes- when the car is surging and I stop the idle jumps all over the place- from 600-900 rpm. Warmer air and the car does not surge and idle is stable at 700 rpm. What you and the next post both suggest are identical- bad or dirty throttle body. Makes sense. Will let you know. Thx!

Bruce In Philly

Remove the air box and spray the TB with TB cleaner... Then ram a cloth in there with a screwdriver ....Repeat . A manual I saw years ago said not to spray solvent into the butterfly pivot pins (?) But I did anyway. No more surging.

Peace​
Bruce in Philly

Highpox1

Gentlemen- it's been a pleasure. Tip of the hat to Bruce in Philly and Rod928, and the rest of you guys; this was indeed an education. The reason for this surging, and unstable idle in colder air was--- a very dirty throttle body. The dealer here in Houston actually acknowledged that could be the problem when I told him what our forum recommended. I brought it over, and they volunteered to clean it. I sat w the mechanic, and he pulled off the rubber inlet, and commenced to spray and brush the flapper and interior. It rained dirty fluid for 2 minutes. 53K miles and 6 years loaded it up. With what? Can't be carbon, it's upstream of combustion. This is intake air. Dirt & Soot from the exhaust? I am surprised that Porsche does not recommend spray cleaning the MAF and brushing the TB when the air filters are changed out. That just makes sense. You can bet I will be doing that on an annual basis. Not only did the surging go away (today it's 58F, so it would have been bad), but the take off right after starting was smoother. For a long time it would rock a bit when it first started off. This started long before the surge issue.

In doing all of this research, I came across several performance air filters that replace the existing setup. FABSPEED has a carbon fiber version (about $900) that looked great, and claimed +14HP. Not sure if it's worth $64/hp to add it, but it would make access to the MAF & TB easy to clean, and you don't change those filters, just clean them. Any of you guys ever swap out for a performance AF kit?

Petza914

Do a search on intake options and you'll have more reading than you ever wanted on both sides of the topic.

DC911S

You won't need to clean it every year. Most manufacturers recommend it every three or four years. Its very odd that Porsche does not include that in the maintenance schedule. My Cadillacs did and so did my Acuras. In fact I had the BG cleaning done in both every three or four years . That cleans the TB and the intake tract. As for AF I use the BMC's and the OEM airbox.

jdgamble

Awesome use case and great that you got this solved... been following quietly. Hey question... what cleaning agent did they use to clean it?

docdrs

I love it when in the age of technology it comes back to the basics...... clean it