Comanche_699

So, I searched the threads, searched the other forums, and searched the google - but I'm not finding anything similar to my experience tonight.

It's a lurching kind of thing, but not like folks have described with throttle plate or clutch issues I've read about. It came on suddenly, I was in the middle of a glorious after work drive down the coast on Highway 1 from Mill Valley out to Bolinas and back. I got a new set of front Michelin PSS and 4 wheel alignment this morning, and a relatively major service last week, plus new brakes - so it was kind of a victory lap.

On the way back up the mountain from Bolinas, in 2nd gear the car started lurching and the motor was all, "RAA RAA RAA RAA RAA" with a synchronized lurching. (you could substitute ra ra ra ra with lurch lurch lurch lurch) This was consistent, regardless of whether I was in 1st, 2nd, or 3rd - and stayed in the "Bucking Bronco" mode until about 5200 RPMS, at which point, it did seem to mellow out and act normally.

Once off the throttle, it would happen again and again, all the way home.

On the freeway, this was still present, and in all gears on up into 6th, but the issue was most prominent between about 3200 and 4000+ RPMs. It did seem to mellow out and behave normally above 5,000 RPM's consistently, but it was really a buckin' bronco anywhere between 1500 and 4000.

At idle the needle sat pretty much pegged around 800, or whatever one click below 1,000 represents. Smooth and steady. In neutral, I could rev up and down, and there was no choppiness, no apparent sounds of 'missing' cylinders, or even unusual popping or back pressure - just the normal growl. Once in gear, the issue was present.

unfortunately, I was in the mountains and with the top down, so there were some other noises at play, but I did try to record some with my iPhone. I mostly had to stay in 2nd, because the road's pretty twisty, and shifting and steering and holding the camera was tough with only the 2 hands.


I'm going to try and park a video here - but do any of you have any ideas what may be going on even without the video?


DROPBOX LINK
https://www.dropbox.com/s/lvdofghdmq..._7835.MOV?dl=0

VIMEO LINK

When the video loads, you'll hear the motor going RA RA RA RA RA in parts, as though i'm stabbing the throttle, but I promise you I'm not. Foot is steady on the throttle (I even pan down to try and prove it!), even under acceleration and deceleration I am being very deliberate in the pedal actuation because I'm making the video. The tach needle hopefully helps to illustrate the issue, and the rocking of the camera is a dumbed down version of the feeling the driver or passenger feels while the car bucks up the hill.

Oh - this also doesn't happen at all when off the throttle, and coming down the mountain, I put it in neutral for a mile or so and the car behaved normally.

If this has been covered extensively in some other thread, I honestly can't find it and would appreciate it if you could share the link, instead of telling me search is my friend, because at least in this case, search has been kind of a dick for the past hour or so.

Thanks for your input -

- Dan

808c2s

Do you have a Durametric? Try reading out the code. It might be a soft code that does not cause a CEL yet. This might give you an idea. When was the last time you cleaned out your MAF? How many miles do you have on the car?

Comanche_699

I do not have a Durametric - I'm a Mac guy, and I didn't want to buy a PC just for a cable, I kept thinking one day there would be support for a mac - but it may be time to get a little PC for the garage.

The car has 73,55x today.

I haven't cleaned the MAF myself - though it was just in for a major service on Friday of last week - I will ask if they got in there while they were going through the car - here's what I had on my service sheet:

• New Rear Brakes - (complete, rotors, pads, all the bolts & shims & what-not)
• Brake Flush (ATE Super Blue)
• Washer Fluid
• Cabin Filter
• Air Filter
• Spark Plugs
• Drive Belt
• BG44k Decarbonizer
• Transmission Gear Oil (Swepco)
• Hand Brake Adjustment
• Fluid Temp check - (Verifying gauge accuracy)
• Reset Tire Pressures (34f / 38r)
• Lube soft top mechanicals

* a complete revisit of the PPI checklist, reviewing the car top to bottom, front to rear.

- Dan

808c2s

Hehehe, I doubt they removed and cleaned the MAF. My car has ~40k on the odometer, and my MAF got dirty. Car started bucking from a dead start until I rev above 3000, then it ran ok. Did the Durametric check, which pointed to the MAF. I took out the MAF, cleaned it with MAF cleaner, reinstalled it, and the car ran fine since. You can just try removing the MAF, cleaning it with MAF cleaner, and see how the car responds. You can also go to Oreilly's or Jiffy Lube type of place and have them scan your car with an OBD scanner to see what the codes are. Sometimes the MAF can malfunction, in which case, you will have to replace it. It's a BOSCH MAF. Pretty cheap on eBay or Amazon.

Comanche_699

I definitely like your thinking, and it seems like a likely culprit. I'll dig into it tomorrow and report back for sure. Thank you for your help. I really appreciate it.
- d

Square

I have never worked on Porsches (and I am not a mechanic), but I have had similar situations where the throttle position sensor was the culprit.

I agree with 808c2s on getting the codes checked.

jhbrennan

Durametric works fine on a Mac running Windows VM

http://support.apple.com/kb/HT1461?v...S&locale=en_US

I use Parallels on a Mac Air and no problems.

Comanche_699

^^ Oh that's clever! Don't know why that never occurred to me. I'm gonna get one now. I've missed a few on CL over the past year at good prices too!

BIG smoke

I ordered this. Thought it was worth the ten bucks. I have not used it yet ...

user 72902

Those are great but even more practical if you have one that links to a smart phone rather than a computer.

USMC_DS1

+1... BTW cleaning the MAF is a cheap/easy way to resolve or at minimum eliminate dirt as the issue within the MAF as the potential culprit if you don't have a Durametric tool. But if you plan on doing some DIY maintenance then a Durametric would be an essential diagnostic tool to have on hand. I noticed from your video that you're in Sports mode... does this occur in the normal driving mode as well? It also appears that you have an airbag error. Was your center console recently removed for some reason and the car was turned on and/or driven with it disconnected. Kinda strange that the p-dealer did not reset the airbag error light while the car was in for service. Have your ignition coils been replaced and when? Looks like the drive was during a clear weather day but was the car recently washed? perhaps at the p-dealer when it was serviced?

Comanche_699

USMC_DS1 - Thanks. Yes, the issue was persistent in with PASM on and off.
The Airbag Light is being thrown by the front left sensor on the passenger seat. Apparently there are 4 in the seat. The dealer wants like $2k for the part, and I'm not on board with that yet. (The passenger seat is empty 98% of the time.) The service is handled by my Indy - I've worked with my mechanic on the airbag sensor a few times, and we're looking for a solution that doesn't require me to buy a whole new seat frame.

Here's what we found today- Cylinder 6 was misfiring somewhere between the 1800 & 3800 range. We put the car up on the lift and pulled the spark plug and coil. The plug was of course brand new and looked fine, the coil also had no cracks and appeared to be perfectly fine - this made me a little nervous.

We pulled number 5, and swapped the coils. Buttoned it down and started the car up. Thought process was, that if 5 was misfiring now, that we had a bad coil. - but it never missed.

So we both looked at the ghost in the machine, and scratched our heads.

Took the car out for a drive, drove it through all the ranges, right on up to the notches above 6500, and back down again - no bucking, no hitches, no nothing.

Back at the shop, we scratched our heads again at how this could be, but there it was. I got in the car and drove to work.

After work, I took it for another drive out to the coast, same route but with a little more gusto. Caught the sunset above Stinson Beach and then raced out to Olema, and then turned around and came right back down the coast and over the mountain - the car performed perfectly, as if nothing had ever happened.

So, I haven't really got a good answer for what it actually was. But I do have a picture of my car hanging out with grampa this morning.




I will still clean the MAF, and I will definitely pick up a durametric, but like the idea of the dodocool too, wireless to android? that's amazing.

And thank you everyone for your help. I'll update if the ghost returns...

- Dan

david

Good to hear that the issue has resolved itself (with Devin's help?!)

Unsure when you were at Hi-Tec but I dropped my 997 off for the 40k at ~1:30pm on Thursday and hope to fetch it later today after doing some heavy lifting with 5 coeds (including daughter #2) at UCD moving from them from one house to another.

gpjli2

My 2006 had similar incident some 7 years ago! Episode of hesitation and surging under acceleration. Started without warning and lasted throughout a 20 minutes or so drive around town. I took car home and restarted it next day and it was gone. At that time there were several other posts describing this. The bottom line was that it went away and never returned. Guesses were made as to whether it was gas related or whether ecu need a reset. I switched to Shell and have stayed there since but that is classic superstitious behavior. My guess is that you experienced this gremlin and most likely will never see it again

Comanche_699

gpjli2 - thanks! i've been a Shell man for no particular reason starting with this car. I've always been a Chevron user, but this car for some reason just pulled in all by itself to a Shell station one day, and it's been going there ever since.

David - that's crazy we're like orbiting within only a few miles of each other constantly. Devin was actually working on a sweet 3.2 liter 914 (Blu Hun) when I was in. Thorsten is my go to in that shop, but they're all very accomplished and badass.

I was in yesterday morning (Thursday) by 8:30am and back to work with the car by 10am.

Here's quick shot from last night, in that last pullout above Stinson, just as the sun was hitting the fog over Bolinas -



Good times,

- Dan