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I supported Toymods
Location:
Epping, Sydney
Registered:
May 2002
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jerky trailing throttle
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Sun, 24 July 2005 01:57
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This has been a problem for a while now, and in stop-start traffic it's starting to piss me off.
When I go from trailing throttle to accelerating, no matter how lightly I tap on the loud pedal my car jerks into acceleration rather than making a smooth transition... any ideas on possible causes?
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Registered:
August 2002
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Re: jerky trailing throttle
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Sun, 24 July 2005 02:12
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Bad tuning hesitation?
Lose tailshaft bolts
Too much play in the diff
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Location:
Terrigal
Registered:
May 2002
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Re: jerky trailing throttle
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Sun, 24 July 2005 06:48
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Is it factory ECU? If so, i'd say TPS is out of adjustment.
If its aftermarket.. Then more likely running a bit lean on that section of the map.
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I supported Toymods
Location:
Epping, Sydney
Registered:
May 2002
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Re: jerky trailing throttle
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Sun, 24 July 2005 15:41
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tailshaft bolts are fine. diff is a possibility, but there have been no other symptoms of it gong out thus far.
it's an aftermarket ECU... you're suggesting it's running a bit lean on trailing throttle or on very low throttle?
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: jerky trailing throttle
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Sun, 24 July 2005 20:21
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| TurboRA28 wrote on Sun, 24 July 2005 16:48 |
Is it factory ECU? If so, i'd say TPS is out of adjustment.
If its aftermarket.. Then more likely running a bit lean on that section of the map.
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it is DEFINITELY too lean on the trailing throttle 
i had zactly same issues when tuning the MS..
if you lean it out too much, as soon as you even touch throtle, it kicks and jerks..
two ways to adjust.
one is to bump up the acel enrich and decrease trigger V/s , but the prob is then you have fuel squirting in all over the shop.
better solution is to bump up the full trailing throttle values by a bit... depends how your ECU measures them 
i think for mine, i increased so that rather than being stoich at trailing throttle, it is just on the rich side (as measured by narrow band sensor) and it may only be a 1-2% (of max injector PW) that makes all the difference, which makes it what.. 0.1 to 0.2ms perhaps??
try setting a certain rpm band... sayy.. 3500rpm to have richer trailing throttle.., and then drive and see difference between 3500 and 4000...
anyhoo, easy fixed of aftermarket
Cya, Stewart
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I supported Toymods
Location:
Epping, Sydney
Registered:
May 2002
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Re: jerky trailing throttle
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Mon, 25 July 2005 00:12
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ah bugger.
I purposefully pulled a bit of fuel from trailing throttle 'cause it was blowing a bit of smoke at idle. might have to put that back up and pull it out of the temp maps.
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Registered:
August 2002
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Re: jerky trailing throttle
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Mon, 25 July 2005 09:17
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| draven wrote on Mon, 25 July 2005 10:12 |
ah bugger.
I purposefully pulled a bit of fuel from trailing throttle 'cause it was blowing a bit of smoke at idle. might have to put that back up and pull it out of the temp maps.
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This could have been a nice piece of information to let everyone know about at the start of the thread. 
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Banned by his request
Location:
moved to tamworth
Registered:
July 2002
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Re: jerky trailing throttle
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Mon, 25 July 2005 09:57
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is it standard size throttlebody? sorry for asking but i cant remmeber is it MAP or AIR flow?.manual or auto im guessing manual{i know you like driving}.aftermarket computer or factory?.
mick
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: jerky trailing throttle
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Mon, 25 July 2005 11:11
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| draven wrote on Mon, 25 July 2005 10:12 |
ah bugger.
I purposefully pulled a bit of fuel from trailing throttle 'cause it was blowing a bit of smoke at idle. might have to put that back up and pull it out of the temp maps.
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but how often do you trail the throttle at engine idle speed? the trailing throttle part of the map and the idle should be in completely seperate areas, so it should be easy to just tune the low kpa areas (like 20-40absolute kpa), whereas idle vac should be what? 5-0-80kpa (depending on cams)
why would you pull it out of the temp maps? that will only cause issues with warmup?
which ECU, what tuning parameters do you have available (not one with a stoopid "cruise map"?)
Cya, Stewart
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I supported Toymods
Location:
Epping, Sydney
Registered:
May 2002
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Re: jerky trailing throttle
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Mon, 25 July 2005 15:05
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microwreck.
correct story: a bit of fuel was pulled out of idle, a bit out of cold start. I can't imagine this would really affect my trailing throttle.
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Location:
Adelaide
Registered:
May 2003
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Re: jerky trailing throttle
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Mon, 25 July 2005 15:58
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The other option in there is that the engine is rocking in the mounts. Common with a button clutch. A GZE which was being used in a clubman with a stacks (sp) clutch unit was jerky as all hell on trailing throttle. Its even more noticble in FWDs, such as a friend's AE82 GZE.
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I supported Toymods
Location:
Epping, Sydney
Registered:
May 2002
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Re: jerky trailing throttle
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Tue, 26 July 2005 01:26
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well, I don't have a button clutch or a FWD  will have a looksee tho
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Location:
Adelaide
Registered:
May 2003
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Re: jerky trailing throttle
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Tue, 26 July 2005 01:37
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Heh, i know you dont have a FWD. Come to think of it though, the sprinter is quite shakey at trailing throttle.... probably due to the almost solid engine mounts
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: jerky trailing throttle
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Tue, 26 July 2005 04:07
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| draven wrote on Tue, 26 July 2005 01:05 |
microwreck.
correct story: a bit of fuel was pulled out of idle, a bit out of cold start. I can't imagine this would really affect my trailing throttle.
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it's not trailing throttle as such (in terms of tuning where that sometimes refers to fuel pulled when throttle is closing).. but decel with closed throtle..
this will put your MAP around 20-40kpa absolute, so all ya need to do is to bump the fuel up a percent at a time in that region and you will tune it out..
i admit i am not familiar with the microlebs, but surely you have an actual 2D map of rpm vs MAP to tune from?
any online software i can download?
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Banned by his request
Location:
moved to tamworth
Registered:
July 2002
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Re: jerky trailing throttle
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Tue, 26 July 2005 05:24
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prob pulled a bit to much out comibined decel and cold start.just creep up on it a bit.
mick
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