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.
^ Thanks for the logs Kevin. Where did these come from? Never seen that much timing retard before..
Is this from your logger? Those load values look different.. did you change them?
Had similar issues with my 08 and turned out to be the boot from plenum to the throttle body. Lower part of the boot was almost completely off. Have a look with flash light and mirror.
OK, time for an update. Long story short: I thought the 295s in the rear might cause the problem ( stock is 305), ie. smaller diameter tires, confused AWD system etc. By mistake I managed to pop a fuse for the AWD system. The result was a message in the dash, "PTC Fault". I drove the car like this for a bit, but the hesitation was still there, and the car felt exactly the same. I didn't really try it in slippery conditions.
After this I ordered a Durametric cable, which gave me some more information. The AWD unit was not responding at all. I fixed the blown fuse and erased the fault code. No more error message, and AWD unit responding again.
I also took a log of the bosst pressure using the cable, and I found out that the boost pressure is a bit high. I'm seeing 1.2 bar above ambient in normal mode, not Sport Chrono (or whatever it's called). The dash gauge only says 1.0, so I suspect I have some kind of tune. The ignition timing signal from Durametric seems to be showing slightly lower values than the Torque app, but this could also be due to warmer weather(?).
Any suggestions? I'm thinking I might see if I can get the car reflashed to stock at this point, but I would like to be reasonably sure it's going to fix the problem and I guess that is the hard part.
I didn't do a full 3:d gear pull when logging, becuase the problem mostly shows up around 4000-5500.
Ignition retardation signals from Durametric did not make much sense to me, and not even to the Durametric support guy. Pretty high numbers, don't you think...
Remove your plugs and inspect the gap. Inspect coil packs for cracks.
Interesting, with the 993TT, folks would get the plugs changed, but only to find out years later that only 4 of 6 were changed. This is sort of quick plug change is repeating with the 997TT.
Put some race gas in (100 octane plus) and see if your car runs better.
Thanks Kevin, good points. Before I spend any more time on it I'm going to talk to the dealership that sold the car and see what they can do. The next steps are probably everything on your list.
Time for an update again:
The ECU has been reflashed to stock and the hesitations are completely gone. I'm measuring lower boost pressures (slightly over 1 bar in sport mode) with Durametric, but the car doesn't really feel slower than before, so I'm pretty happy with that (for now). If I decide to do some tuning later on I will probably start with the plugs and coils.
Do fuel pumps fail in a binary fashion or do they slowly die?
What is the best way to diagnose a dying pump? Is there a mileage at which they should just be replaced?
Originally Posted by Kevin
If you got new plugs..
1) New owners might not be familiar with the VarioCam Plus "bump" that occurs between 2700 and 4500 RPM's. You will also have the low lift high lift even happening early on.. It can be a slight shutter depending on load.
2) Knock retard will produce the shutter.. Fill up with RACE GAS>>if you feel the difference, you have your answer.
3) We are starting to see engine sensors degrade. Wideband O2's become sluggish, MAP sensors will get fouled with a oiled filter.
4) Intake leaks, and slight intake leaks..
5) Fuel pressure issues from failing fuel pumps..
Feel free to email me, and I can send you some engine data from 98Ron engine datalogs.
I've been having very similar symptoms to this thread. Have datalogged with a Cobb AP, and found that timing was being pulled due to knock sense, but haven't been able to determine the cause. The plugs and coils have been replaced to no effect.
I would think if it was a fuel problem, I would see the fuel trims maxing out at 1.20, but they look fine. I would also think if the oxygen sensors were failing, there would be some discrepancy between them, but the two banks are very consistent. Maybe a leak in the intake? The AFRs don't look unreasonable to me though. Does anyone have ideas for me? Here's a log:
04-10-2017, 08:31 PM
