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I have owned my first Porsche, a 997.1 TT for about two months now, and started noticing a slight hesitation during full load accelerations. If I do a 3:rd gear pull (in tiptronic mode) from 3000 RPM to redline I typically get 2-3 of these hesitations at roughly the same RPMs each time, for example 3500, 4200 and 4700. It feels like a short decline in acceleration, short enough that a non-car guy probably wouldn't notice. Kind of similar to when traction control is working. Overall performance is not really affected and the car definately feels fast.
Any ideas about this? My first thought is knock control due to bad gas (I use the same gas station every time and suspect that the 98 RON pump might not be used that much). I would however not expect to feel the timing pull that clearly..?
I tried to add a couple of liters of E85 to the tank, and I think it helped. Hesitations are not completely gone but less frequent.
Thanx!
Not that many, about 2000 km = 1250 miles according to the servie log.
I don't know if the car is tuned or not. The stock boost gauge shows 1.0 bar (14.5 PSI) without the Sport Chrono overboost, and MAF reading peaks at 405 g/s according to the Torque OBD app if that is anything to go by.
I have owned my first Porsche, a 997.1 TT for about two months now, and started noticing a slight hesitation during full load accelerations. If I do a 3:rd gear pull (in tiptronic mode) from 3000 RPM to redline I typically get 2-3 of these hesitations at roughly the same RPMs each time, for example 3500, 4200 and 4700. It feels like a short decline in acceleration, short enough that a non-car guy probably wouldn't notice. Kind of similar to when traction control is working. Overall performance is not really affected and the car definately feels fast.
Any ideas about this? My first thought is knock control due to bad gas (I use the same gas station every time and suspect that the 98 RON pump might not be used that much). I would however not expect to feel the timing pull that clearly..?
I tried to add a couple of liters of E85 to the tank, and I think it helped. Hesitations are not completely gone but less frequent.
Buy your gas from a busy station to ensure you get the freshest gasoline. I stick with top tier gasolines with Chevron my preferred brand. But Shell or Texaco or Philips 66 are good too.
Do *not* use E85 in any ratio with premium gasoline.
What is the car's condition? That is when were plugs last changed? How many miles are on the coils? The O2 sensors? Even the engine air filter?
These engines are pretty highly tuned from the factory and plugs, coils, O2 sensors, and certainly engine air filter condition are all very important to getting the most from the engine.
Another thing to consider is running a bottle or two of Techron through the engine. Just dump the entire bottle -- the ones I buy/use treat 20 gallons of gasoline -- into the fuel tank and then fill up with the correct octane of gasoline.
Drive the car normally. The general rule is if you feel any improvement from the engine to run a 2nd bottle through after the fuel tank level is down to say 1/4 of fuel left. I'd run a 2nd bottle regardless.
After the 2nd tank of fuel is down to 1/4 of fuel left it is a good idea to change the oil/filter.
While the behavior doesn't necessarily suggest a "problem" in this area, it couldn't hurt: Perform a calibration of the e-Gas system. The instructions for this should be in the owners manual.
For my 2003 Turbo with one's foot off the gas pedal through the entire procedure, turn the key to on and leave on for at least 60 seconds. Then turn the key off for at least 10 seconds. The next time the engine is started the calibration is complete.
Buy your gas from a busy station to ensure you get the freshest gasoline. I stick with top tier gasolines with Chevron my preferred brand. But Shell or Texaco or Philips 66 are good too.
Do *not* use E85 in any ratio with premium gasoline.
What is the car's condition? That is when were plugs last changed? How many miles are on the coils? The O2 sensors? Even the engine air filter?
...
Great, thanks!
I would say very good condition. 71000 miles. Plugs and air filter changed 1200 miles ago. Don't know about coils and O2-sensors. Can the coils go bad without throwing codes? When a coil on my Seat Leon 1.8T died at speed I got a flashing check engine light and some pretty wierd noises.
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.
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.
...
Thanks Kevin. E-mail sent about logs.
I think I know what you mean by "bump" and I think I feel that as well, but it feels like it should be there in a different way than the shutter.
Great, thanks!
I would say very good condition. 71000 miles. Plugs and air filter changed 1200 miles ago. Don't know about coils and O2-sensors. Can the coils go bad without throwing codes? When a coil on my Seat Leon 1.8T died at speed I got a flashing check engine light and some pretty wierd noises.
My experience with my 2003 Turbo is the coils can go off yet not throw codes.
Seemingly contradicting myself my car was throwing misfire codes at cold start. As is my habit after I cold start one of my cars I like to let the engine idle until the secondary air injection pump shuts off and the cold idle speed drops to near its normal hot idle level. This is when the DME switches from open loop model to closed loop mode.
The CEL would come on in around 30 to 40 seconds. Always the same cylinders. After starting the engine I'd be kind of busy with the seat belt, taking stock to make sure I didn't forget anything before leaving the house, and just kind of taking time to think about things and about the time I think "the engine's idling a bit rougher than usual" the CEL would come on. Except for the slightly rougher running engine and then the CEL there was no other drama associated with the misfires at cold start.
The engine would never misfire at any other times. There were no other symptoms.
Since the coils were original and had over 130K miles on them I had the coils and plugs replaced, even though the plugs were not that old, in fact they had about 10K miles left until they were due to be changed again.
After the new plugs and coils were installed the engine ran remarkably better. Since I have had the plugs changed a couple of time prior to this with no change from the engine I attribute the improvement to the coils.
The misfires remained as before. (I'll save you the suspense: To fix the misfires I just stopped letting the engine idle after cold start.)
Might add that on a drive back from the mid-west started getting an O2 sensor error code related to a sensor heater problem. Engine ran ok though. But when I got home since the car was due, past due, for a smog check needed to register the car I booked the car in and had all 4 sensors replaced.
Similarily with the coils being replaced after the new O2 sensors were installed the engine ran remarkably better. I've never changed the sensors on the Turbo before so this was a new experience for me. I have had the sensors in my Boxster replaced before and while the new sensors addressed the error codes the engine never ran any different afterwards that I could tell.
(After a day of driving the car around to ensure all was OK I booked the car in for a smog check and it passed with flying colors.)
Macster: Interesting story. Could be very useful information, for me or someone else.
I have some actual data now. Third gear pull, still with the suspected low quality gas in the tank, but that is just a theory. I felt 3-4 of the shutter events during the pull. Any comments? Anything suggesting some kind of tune? Boost is not measurable with the Torque app. Stock gauge shows 1.0 bar = 14.5 PSI.
AFR vs RPM
Ignition timing (cyl1 or average?). Lower part is acceleration
This is a customers datalog (stock) file using the Ultimate Motorwerks datalogger. Sport Chrono engaged.
Stock original ECU map. I verified it.
The ECU is pulling timing (blue circle) and pulling boost (mustard color) should register 1 bar, you can also see the variable vane (N75) slowing down the turbine>>intentional
Green is engine load which is bouncing around
The ignition angle underlined in RED is VERY low. The result is a hesitation that you can feel.
04-09-2017, 07:53 AM
Slight hesitation during hard acceleration
Anything suggesting some kind of tune? Boost is not measurable with the Torque app. Stock gauge shows 1.0 bar = 14.5 PSI.
