a tune will not dfiz a mechanical issue if any. Unless you had a bad previous tune then that would explain it. However, if your running now mafless, before you were not, then that would explain your success.
To all: unplug the made harness and try to duplicate the issue. That simple

 

Cleaned the TB and new Fuel filter. TB cleaning made a big difference so far but might still be a teeny tiny hesitation. tonight I changed my fuel filter and that looks pretty darn dirty. will run for a few hundred miles and see what happens. If the snow and ice give a break)

 

Ok. How many degrees does it sway?
Regarding TPS, is the TPS stable when hesitation occurs?


Is there a dead spot in the TPS circuit? ie not linear?

 

I'm watching this thread with interest, as I have a small 'miss' when making very slight throttle adjustments in the 3K range on the freeway. Both accel and decel. It feels as if the spark plugs don't fire for a millisecond. Did not change when I applied ECU tune. Almost seems TPS-related, but as Sambo points out, there are a lot of things interconnected on this engine.

 

Looks like some guys are making headway with the typical things being addressed. Anyone feel free to reach out if I can help! With more fuel, timing advance, boost and so on weaknesses will start to say hello. From vacuum leaks to spark plugs to dirty fuel filters and throttle bodies. There's just a lot on 15-year-old cars. The nice thing is that it generally always gets worked out and you end up having a very solid running car.

 

Exactly, first job was to use your boost leak testing kit to find and replace all leaks (thanks again for the pointers). Once that was done, I took the car to my local tuner and he said it was definitely an issue with the tune. Once it was reflashed with the Cobb, problem went away - I'm at about 200 miles so far with zero hesitation/surging.

What does removing the MAF harness tell you? Assuming 2 different cars, and similar mods, let's say one guy was able to duplicate the issue, and the other guy cannot? What's the next step in diagnosing the issue for these 2 cars?

 

As others have said, most likely there is a hardware issue or leak. My shop just found a large hole on the hose connected to the N75 valves. I'm not exactly sure how that would change things but could certainly do some harm and cause drivability issues with surging/boost issues.

Whole car is getting checked out in prep for impending track season: fluids, nut bolt, caliper rebuild, boost leak check... Amazing what a good shop can find!

 

Sounds to easy, but check your air filter. I had a k&n and due to the color was hard to see how dirty it was. Changed back to paper and hesitations vanished. Doing an e gas reset is just as easy and free to do as well.

 

Finally, finally after 1.5 yrs. of trying to find the cause I did it.

When I bought the car over 2 yrs ago there was slight hesitation at lower rpm's and I started with changing the plugs + coils at a local garage. -no improvement.

-Recently changed all the check valves, #16 was bad!, zip tied all the vacuum lines. At the same time IPD plenum in (because I broke the stock one &#128556 BUT! no joy.

-Leak tested, rock solid 25 psi.

Then I decided to start another round.. bought Denso PK-PR8 double platinum plugs and new uprated coils.
This time I was in the repair shop to see what's up and after removing the first coil and a plug I was shocked.. -The coils were from Boxter, and 50% smaller. Plugs were so dirty I'm suprised the car even started. Apparently this car runs "ok" with Boxter coils as I drove 5000km with them, having only a slight hesitation at around 2000rpm.
So the hesitation is gone and I have no plans to sell my car anymore. I love it!

Btw, it'll be interesting to see the power gains on a dyno. With those Boxter coils 497 RWHP/750nm., Mustang dyno.
It pulls like a freight train after the new parts!
So if you haven't changed the plugs/coils your self, I would start with that.

good luck.

 

did you not the difference in size when you change the coils 2 yrs ago? what part # were the coils you in stalled 2 yrs ago versus the coils you installed now?

 

Bosch 0986221016. Actually when I googled more, some sources say it's compatible with 997 turbo.
I was not there when they changed them first time. Parts came from them.
the new one is BERU ZS178. Remarkably bigger, and came with longer bolts.

 

sounds like the latest version of coils. doesnt mean the others were the wrong coils.

 

I've always run Bosch 0986221016 Ignition coils on my built engine. Yes, a Boxster part number. They are the Bosch equivalent of the original BERU coils. That is what my tuner recommends for all his modified engines. I've had zero issues with these.. Your issues were likely your plugs, not the coils unless they were cracked or damaged somehow.

 

I have high-performance coils since I had the same issues described above when I first bought my TT. My coils are Plasma-direct made by Okada. They produce far more spark than the "normal" coils and cause the engine to run incredibly smoother - even if your engine was running smooth in the first place. (they are guaranteed for life)

On the last plug change, I though I would take advantage of the extra spark and I opted for the 4-electrode plug NGK BKR6EQUP 3199. I don't know how this plug would perform or last with "standard" coils, but for me, they seem to deliver a very good level of performance. So far I am very happy. I'm just relating my experience here to illustrate other options for ensuring that hesitation doesn't affect your ride.

 

Anyone tried ip/ okada coils? They work great in bmw and the car picked up much faster