Revs up by itself between shifts?
12-27-2019, 05:58 PM
#91
Member
Join Date: 02-04-2014
Location: Garrison, KY
Posts: 47
I posted in this thread many years ago. I still own my SS and the reving is clearly the shift anticipation code working normally.
If you've every seen the official GM program code listing for one of their manual trans cars, it's right there. In the 80's and 90's it was more crude in that it would just not let the RPMs dropped when you clutched it. It made the engine/trans RPM matching must better. Then if you clutched it and rolled to a stop, the RPMs would hold around 1500 and then slowly drop over a couple of seconds. Depending on the code, it was was around 10-15 MPH. The programmer assumed you were coming to a stop. Drove people nuts trying to decide if something was wrong, but it's not.
As faster processors came along and they added clutch pedal sensors they could better predict what you were about to do. It is possible to fool it so that you get that high rev up. If you rev the engine in gear and then quickly clutch it, it will probably hold high. But generally it won't happen in normal shifting. On the other hand, if you are banging gears it greatly improves the synchronization of the engine RPM to the trans input shaft speed for the next gear.
Bottom line - you're trying to fix something that isn't broken. If it holds more than 5 seconds without dropping, then yes, something is wrong. Mine always starts to drop after a few seconds.
If you've every seen the official GM program code listing for one of their manual trans cars, it's right there. In the 80's and 90's it was more crude in that it would just not let the RPMs dropped when you clutched it. It made the engine/trans RPM matching must better. Then if you clutched it and rolled to a stop, the RPMs would hold around 1500 and then slowly drop over a couple of seconds. Depending on the code, it was was around 10-15 MPH. The programmer assumed you were coming to a stop. Drove people nuts trying to decide if something was wrong, but it's not.
As faster processors came along and they added clutch pedal sensors they could better predict what you were about to do. It is possible to fool it so that you get that high rev up. If you rev the engine in gear and then quickly clutch it, it will probably hold high. But generally it won't happen in normal shifting. On the other hand, if you are banging gears it greatly improves the synchronization of the engine RPM to the trans input shaft speed for the next gear.
Bottom line - you're trying to fix something that isn't broken. If it holds more than 5 seconds without dropping, then yes, something is wrong. Mine always starts to drop after a few seconds.
01-04-2020, 10:48 PM
#96
Member
Join Date: 02-04-2014
Location: Garrison, KY
Posts: 47
If you read through the entire thread, it seems to be deeper than that. Most of the cars with this problem have done it since day one and some have replaced the throttle body and it did not solve the problem.
01-14-2020, 05:42 PM
#97
New Member
Join Date: 01-13-2020
Location: CA
Posts: 18
06-24-2020, 10:09 PM
#99
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Join Date: 05-01-2014
Location: California
Posts: 7,814
Interesting Rocky. Cutting to the end, this video explains why rev hang happens with older, port injected engines.
But when it happens with a very small percentage of our direct injection SS's, there's something wrong. I believe the issue with mine was with the cpp and/or bpp sensor(s). Most likely the cpp sensor.
But when it happens with a very small percentage of our direct injection SS's, there's something wrong. I believe the issue with mine was with the cpp and/or bpp sensor(s). Most likely the cpp sensor.
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