3rd to 4rd gear shift, hard fuel cut?
Thread Starter
Senior Member
Joined: Aug 2010
Posts: 347
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From: Ontario, Canada
2002 C32 AMG
3rd to 4rd gear shift, hard fuel cut?
Hey guys, I've been experiencing a new problem lately. Basically when I go WOT in 3rd gear, when it's about to shift into 4th I get a really hard jerk forward, almost like the TC has kicked in and cut all my power. I have a NW ASP 178mm pulley with NW PSK. I have considered belt slip, but it doesn't happen in any other gears and I don't "hear" any slip. I've had belt slip before in colder weather, usually 1st to 2nd gear WOT, it's definitely not that. I have tried multiple scan tools and no engine codes are showing up either. The only thing I can think of is some sort of fuel cut. I seriously doubt at speeds in 3rd-4th gear, the TC is kicking in. There's no flashing TC light, so I'm pretty sure it's not that either. I had an issue last summer where my AFR's were leaning out around 5500RPM+, but oddly enough that seems to have gone away. I monitor AFR's closely and I don't see any issues with lean air/fuel mixtures. Any idea what could be going on? I have a eurocharged engine tune which among other things, makes the transmission shift faster. I'm wondering if somehow there is too much load on the transmission and it's kind of a failsafe to protect the tranny? It's also not the S/C shutting off due to high IAT's. I have IAT's monitored and my data logger warns me when temps get high enough for the S/C to shut off. It could also be possible that I'm still having this leaning out problem, but I just can't see it on the wideband when fuel cut occurs. If it is fuel cut, I'm just curious as to why multiple fuel cuts wouldn't throw a code. I literally did this 3 times in a row last night.
Any help would be appreciated. Thanks.
Bry
Any help would be appreciated. Thanks.
Bry
Last edited by Autotechnica; May 13, 2012 at 11:33 AM.
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From: murfreesboro,tn
2003 porsche 996 turbo
do you have the tcu mod? i had the same issues from all 3 gears to 4th it was the tps slamming shut during the shift causing a huge afr spike . tps would go from 90% to 6% during the shift while timing and boost stays the same. after the shift the tps shoots back to 98% causing the hard bang shift . replaced the modded tcu with a oem tcu and it all went away this all happens in approx 400 rpm so its hard to see whiule driving . only while examining the zdl files did i find the issue
Thread Starter
Senior Member
Joined: Aug 2010
Posts: 347
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From: Ontario, Canada
2002 C32 AMG
do you have the tcu mod? i had the same issues from all 3 gears to 4th it was the tps slamming shut during the shift causing a huge afr spike . tps would go from 90% to 6% during the shift while timing and boost stays the same. after the shift the tps shoots back to 98% causing the hard bang shift . replaced the modded tcu with a oem tcu and it all went away this all happens in approx 400 rpm so its hard to see whiule driving . only while examining the zdl files did i find the issue
Thread Starter
Senior Member
Joined: Aug 2010
Posts: 347
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From: Ontario, Canada
2002 C32 AMG
Hmmm anyone with a 178/185mm pulley have the same problem? Last night I was amongst a crowd of guys with tuned forced induced cars running auto boxes who said that the problem I was describing was common when raising boost on cars with autoboxes. The TCU/ECU does some funny stuff to either protect the tranny or the computer just doesn't know how to shift properly due to the added power. I asked if switching back to the stock ECU tune with the OEM tune's slower shifting would improve this issue. They said no, since delayed shifting will only burn out the clutches in the automatic tranny. Does this sound right? I have 0 experience with automatics as this is my first autobox. One guy with a 600WHP IS300 and automatic told me the only way to get around this is to manually shift 1-2 seconds before the RPM's hit redline and predict when the transmission will actually decide to change up a gear. When I'm at WOT near redline, the TPS will be 100% unless I almost completely let off the throttle, so easing off the throttle before the shift to avoid the hard jerk is out of the question, I have tried this many times and it doesn't work. Another reason I hate drive by wire.
I'm so bothered by this issue, I'm actually considering going back to the stock pulley. To me power is nothing without drivability. Granted, I don't get to do pulls too often that require WOT 3rd to 4th gear shifts, but still. I was going to ask if the TCU tune will fix this issue, but reading the reply above, seems like it makes it worse? Does anyone see any problem with trying out the stock ECU shift pattern? Will that infact burn out my clutches?
thanks.
I'm so bothered by this issue, I'm actually considering going back to the stock pulley. To me power is nothing without drivability. Granted, I don't get to do pulls too often that require WOT 3rd to 4th gear shifts, but still. I was going to ask if the TCU tune will fix this issue, but reading the reply above, seems like it makes it worse? Does anyone see any problem with trying out the stock ECU shift pattern? Will that infact burn out my clutches?
thanks.
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Joined: Mar 2004
Posts: 2,073
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From: North NJ
2002 C32 AMG, 2013 GLK 350/4, 2015 E63S AMG Wagon
I run a 181mm pulley and I don't have this problem. Had it with the EC TC
U tune but it is gone since I went back to the stock TCU. Post your DashDaq log. Maybe something could be learned from it.
U tune but it is gone since I went back to the stock TCU. Post your DashDaq log. Maybe something could be learned from it.
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From: murfreesboro,tn
2003 porsche 996 turbo
ok i have been having the same issues and with my buddys research and my new tune i have licked the problem. do a google search for SUPERCHARGER SURGE. its slamming the butterfly closed with the vacuum and then reopening. its a torque management problem. after 3 hrs on the dyno and 3 hrs with the tuner going over all the files in the ecu we have eliminated it and i then went to the track and ran 12.1 , 12.0 , 11.9 , 12.1
im running a stacked setup with a c3 s/c pulley and a pte 178mm fluidamper crank pulley. pulled 22 lbs boost at wot
the issue originally reared its head only with the esp on. with the esp off it would shift fine. during the dyno run it would happen at part throttle with the esp off.
im running a stacked setup with a c3 s/c pulley and a pte 178mm fluidamper crank pulley. pulled 22 lbs boost at wot
the issue originally reared its head only with the esp on. with the esp off it would shift fine. during the dyno run it would happen at part throttle with the esp off.
Senior Member
Joined: Oct 2010
Posts: 380
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C55 AMG T with Kleemann K2 and some stuff: 414 hp and 562 Nm :-)
If you do the "Sneaky ECU Reset", you can experience this behaviour.
It takes a while before it adapts back, and before that you can
feel a jerk between shifts at full power; it cuts and then it comes on.
It takes a while before it adapts back, and before that you can
feel a jerk between shifts at full power; it cuts and then it comes on.
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Thread Starter
Senior Member
Joined: Aug 2010
Posts: 347
Likes: 0
From: Ontario, Canada
2002 C32 AMG
ok i have been having the same issues and with my buddys research and my new tune i have licked the problem. do a google search for SUPERCHARGER SURGE. its slamming the butterfly closed with the vacuum and then reopening. its a torque management problem. after 3 hrs on the dyno and 3 hrs with the tuner going over all the files in the ecu we have eliminated it and i then went to the track and ran 12.1 , 12.0 , 11.9 , 12.1
im running a stacked setup with a c3 s/c pulley and a pte 178mm fluidamper crank pulley. pulled 22 lbs boost at wot
the issue originally reared its head only with the esp on. with the esp off it would shift fine. during the dyno run it would happen at part throttle with the esp off.
im running a stacked setup with a c3 s/c pulley and a pte 178mm fluidamper crank pulley. pulled 22 lbs boost at wot
the issue originally reared its head only with the esp on. with the esp off it would shift fine. during the dyno run it would happen at part throttle with the esp off.
thanks guys.
MBWorld Fanatic!
Joined: Sep 2008
Posts: 3,152
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From: murfreesboro,tn
2003 porsche 996 turbo
honestly i dont know what the tuner did to fix it other than he worked in the torque limiter files. didnt ask as we were 6 hrs into the dyno day. its something the tuner needs to search for
MBWorld Fanatic!
Joined: Mar 2004
Posts: 2,073
Likes: 27
From: North NJ
2002 C32 AMG, 2013 GLK 350/4, 2015 E63S AMG Wagon
What kind of info should I log? I seem to be having problems getting a good AFR signal from my wideband, so aside from that, I can log everything else. I haven't logged anything yet, so I assume I just start log with whatever signals are displayed on screen and that's what will be logged?
thanks guys.
thanks guys.
Steve, who is the new tuner?
Junior Member
Joined: Dec 2007
Posts: 40
Likes: 0
From: Hong Kong
C32
Hey guys, I've been experiencing a new problem lately. Basically when I go WOT in 3rd gear, when it's about to shift into 4th I get a really hard jerk forward, almost like the TC has kicked in and cut all my power. I have a NW ASP 178mm pulley with NW PSK. I have considered belt slip, but it doesn't happen in any other gears and I don't "hear" any slip. I've had belt slip before in colder weather, usually 1st to 2nd gear WOT, it's definitely not that. I have tried multiple scan tools and no engine codes are showing up either. The only thing I can think of is some sort of fuel cut. I seriously doubt at speeds in 3rd-4th gear, the TC is kicking in. There's no flashing TC light, so I'm pretty sure it's not that either. I had an issue last summer where my AFR's were leaning out around 5500RPM+, but oddly enough that seems to have gone away. I monitor AFR's closely and I don't see any issues with lean air/fuel mixtures. Any idea what could be going on? I have a eurocharged engine tune which among other things, makes the transmission shift faster. I'm wondering if somehow there is too much load on the transmission and it's kind of a failsafe to protect the tranny? It's also not the S/C shutting off due to high IAT's. I have IAT's monitored and my data logger warns me when temps get high enough for the S/C to shut off. It could also be possible that I'm still having this leaning out problem, but I just can't see it on the wideband when fuel cut occurs. If it is fuel cut, I'm just curious as to why multiple fuel cuts wouldn't throw a code. I literally did this 3 times in a row last night.
Any help would be appreciated. Thanks.
Bry
Any help would be appreciated. Thanks.
Bry
Super Member
Joined: Jun 2011
Posts: 601
Likes: 4
From: I liva at da land down under
Porsche 2004 911
Did a retune from Eurocharged cure this? I am getting it at WOT from 2nd to 3rd change(limp when it hits the limiter and throws me forward then shifts and kicks me back) 
BTW I have added a SL55 intake kit since the EC tune 8months ago if that makes a major difference however am pretty sure it would do it on occasion beforehand.
BTW I have added a SL55 intake kit since the EC tune 8months ago if that makes a major difference however am pretty sure it would do it on occasion beforehand.
Last edited by macbryanie; Sep 8, 2012 at 05:37 AM.
