Occasional short engine hesitation

magnust · 03-10-2012, 09:04 PM

Sorry, had to edit below a little bit, I went out for a drive and it really happens on lower rpm's than I initially wrote. This below should be more correct now:

Now and then I get a short engine hesitation when I do this:

- short shift and get into fourth gear at around 1900-2000 rpm.

- go slowly from roughly 20-30% gas pedal to 60-80%

- rpm rises aprox. 500-600 more rpms

- then just slightly lift of the gas, just a tiny bit

I sometimes then get a sudden engine hesitation, shudder. Like if I had very quickly lifted of the gas to 0% and then pushed back up again. It's just a short hesitation and then the engine pulls correctly, correct for the pedal position. It also happens at the same rpms in third gear, the main thing seems to be low rpms and a bit of load, a slight upphill for example.

I've thought this is a consequence of the special ECU without air mass sensor the CSL uses. But maybe it shouldn't do this. So I'm very curious, anyone else have this issue?

**cantfind1** · 04-10-2012, 01:21 PM

Have you had your Head Gasket checked recently?? ie leak down test....

magnust · 04-10-2012, 01:49 PM

Yep, head was taken of and returned with new gasket.

Trawler · 04-10-2012, 07:52 PM

I've had what feels like a flat spot in 4th at those rpm (2000 - 2500). Similar sensation I suppose. Used to get it on my old E36 M3. Never had it when I rember to keep the revs up, that is 3rd gear at the same road speed.

The Gorilla · 05-10-2012, 10:51 AM

Hi,

Put the Car into Sport Mode, and although
the Throttle response is a lot quicker does
the engine still suffer from same/sort issue ?

If not, maybe Coil/s ? if still running Bremis,
they are known to do some strange things,
or could just be a combination of 4th gear,
low rpm , engine load, fuelling etc

Regards,

The Gorilla.

**outnumbered** · 05-10-2012, 11:15 AM

My car does this, as did my old E46 M3.

magnust · 05-10-2012, 01:11 PM

My initial post was not correct, here's more correct. As you can see below it's low rpm,s and a bit of load, that's key, slight uphill in third or fourth for example.

- short shift and get into fourth gear at around 1900-2000 rpm.

- go slowly from roughly 20-30% gas pedal to 60-80%

- rpm rises aprox. 500-600 more rpms

- then just slightly lift of the gas, just a tiny bit

The Gorilla · 05-10-2012, 02:27 PM

Hi,

I am guessing that its a combination
of the Transistion from cold air intake
valve closing and TB's kicking in
under low rpm and the drivertrain load
in 4th gear. [low inertia]

Similar symptons can be experinced at the
''twisties'' with DBW, where pending your
driving style you get ahead of the
Stepper motor, to the point where
the engine actually starts hesitating.

Regards,

The Gorilla.

03-10-2012, 09:04 PM	#1
magnust S4 - Getting the hang of it Join Date: Jan 2011 Location: Stockholm, Sweden Posts: 138 Casino cash: $1477	Occasional short engine hesitation Sorry, had to edit below a little bit, I went out for a drive and it really happens on lower rpm's than I initially wrote. This below should be more correct now: Now and then I get a short engine hesitation when I do this: - short shift and get into fourth gear at around 1900-2000 rpm. - go slowly from roughly 20-30% gas pedal to 60-80% - rpm rises aprox. 500-600 more rpms - then just slightly lift of the gas, just a tiny bit I sometimes then get a sudden engine hesitation, shudder. Like if I had very quickly lifted of the gas to 0% and then pushed back up again. It's just a short hesitation and then the engine pulls correctly, correct for the pedal position. It also happens at the same rpms in third gear, the main thing seems to be low rpms and a bit of load, a slight upphill for example. I've thought this is a consequence of the special ECU without air mass sensor the CSL uses. But maybe it shouldn't do this. So I'm very curious, anyone else have this issue? __________________ My Swedish track day / hobby racing site: www.rejsa.nu Last edited by magnust; 05-10-2012 at 01:09 PM.

04-10-2012, 01:49 PM	#3
magnust S4 - Getting the hang of it Join Date: Jan 2011 Location: Stockholm, Sweden Posts: 138 Casino cash: $1477	Yep, head was taken of and returned with new gasket. __________________ My Swedish track day / hobby racing site: www.rejsa.nu

05-10-2012, 11:15 AM	#6
outnumbered S5, Sport Off, DSC M-track Join Date: Nov 2009 Location: Reading Posts: 731 Casino cash: $19587	My car does this, as did my old E46 M3. __________________ Now with added SG CSL.

05-10-2012, 01:11 PM	#7
magnust S4 - Getting the hang of it Join Date: Jan 2011 Location: Stockholm, Sweden Posts: 138 Casino cash: $1477	My initial post was not correct, here's more correct. As you can see below it's low rpm,s and a bit of load, that's key, slight uphill in third or fourth for example. - short shift and get into fourth gear at around 1900-2000 rpm. - go slowly from roughly 20-30% gas pedal to 60-80% - rpm rises aprox. 500-600 more rpms - then just slightly lift of the gas, just a tiny bit __________________ My Swedish track day / hobby racing site: www.rejsa.nu Last edited by magnust; 05-10-2012 at 03:45 PM.

04-10-2012, 01:21 PM	#2
cantfind1 S5, Sport Off, DSC M-track Join Date: Oct 2009 Location: Sydney Australia Posts: 675 Casino cash: $6490	Have you had your Head Gasket checked recently?? ie leak down test....

04-10-2012, 07:52 PM	#4
Trawler Driving it like I nicked it Join Date: Dec 2008 Posts: 2,213 Casino cash: $25916	I've had what feels like a flat spot in 4th at those rpm (2000 - 2500). Similar sensation I suppose. Used to get it on my old E36 M3. Never had it when I rember to keep the revs up, that is 3rd gear at the same road speed.

05-10-2012, 10:51 AM	#5
The Gorilla S5, Sport Off, DSC M-track Join Date: Apr 2008 Posts: 740 Casino cash: $14401	Hi, Put the Car into Sport Mode, and although the Throttle response is a lot quicker does the engine still suffer from same/sort issue ? If not, maybe Coil/s ? if still running Bremis, they are known to do some strange things, or could just be a combination of 4th gear, low rpm , engine load, fuelling etc Regards, The Gorilla.

05-10-2012, 02:27 PM	#8
The Gorilla S5, Sport Off, DSC M-track Join Date: Apr 2008 Posts: 740 Casino cash: $14401	Hi, I am guessing that its a combination of the Transistion from cold air intake valve closing and TB's kicking in under low rpm and the drivertrain load in 4th gear. [low inertia] Similar symptons can be experinced at the ''twisties'' with DBW, where pending your driving style you get ahead of the Stepper motor, to the point where the engine actually starts hesitating. Regards, The Gorilla.