Very slow return to idle after full release of accelerator
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Teching In
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From: California
Very slow return to idle after full release of accelerator I have an 02 Z28 M6 with a very annoying problem. After getting on the throttle and letting off, it takes forever for the car to return to a normal idle. Did the GM folks tweak something to make this intentional? It’s just really annoying to run up through the gears then let kick it in to neutral and have your engine still whining away at 5k rpm. I have heard there was some type of modification to some electronics in the throttle body that can fix this. Does anyone know what this fix is???
Re: Very slow return to idle after full release of accelerator Check for vacuum leaks as well. I would say look at the EGR into the manifold but you don't have that. Mine did that and that was my fix.
Thread Starter
Teching In
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From: California
Re: Very slow return to idle after full release of accelerator Thanks for the info. I hooked up the vacuum meter and didn't find anything odd. It almost seems that GM was trying to put some sort of delay on the engine winding down. I had heard that there was an electric servo that may override the cable from the pedal. I'm just hoping to get to the bottom of this by the end of the weekend. Does anyone else in a 2001 0r 2002 have this same problem?
<small>[ May 24, 2002, 08:11 PM: Message edited by: a_dork ]</small>
<small>[ May 24, 2002, 08:11 PM: Message edited by: a_dork ]</small>
On The Tree
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From: Indian Trail N.C.
Re: Very slow return to idle after full release of accelerator </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by a_dork:
<strong>Thanks for the info. I hooked up the vacuum meter and didn't find anything odd. It almost seems that GM was trying to put some sort of delay on the engine winding down. I had heard that there was an electric servo that may override the cable from the pedal. I'm just hoping to get to the bottom of this by the end of the weekend. Does anyone else in a 2001 0r 2002 have this same problem?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Yes I do. Mine's a 2001 and I've just gottne used to it but it was difficult.
<strong>Thanks for the info. I hooked up the vacuum meter and didn't find anything odd. It almost seems that GM was trying to put some sort of delay on the engine winding down. I had heard that there was an electric servo that may override the cable from the pedal. I'm just hoping to get to the bottom of this by the end of the weekend. Does anyone else in a 2001 0r 2002 have this same problem?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Yes I do. Mine's a 2001 and I've just gottne used to it but it was difficult.
TECH Senior Member
Joined: Nov 2001
Posts: 7,234
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From: Mississauga, Ontario
Re: Very slow return to idle after full release of accelerator Without driving your car it's hard to say if your car falls in the normal range or not, but it is written in the programming that after the rpms are high, the car does not return to idle instantly, but instead comes down a bit slower. This is mainly to prevent stalling I believe, but it also may have something to do with emissions, as I believe a rapid descent in the rpms like that could harm the catalytics in some way (I am not 100% sure on this though, it was a rumor I heard in the past)
Thread Starter
Teching In
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From: California
Re: Very slow return to idle after full release of accelerator Thanks for the info. I'm tracking down some information through a friend who works for a car dealer in town. When I get to the bottom of it (cure or not), I'll post the facts here.
Teching In
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From: Hamilton, ON, CANADA
Re: Very slow return to idle after full release of accelerator I have a '01 SS and it does the same thing! I dont think its something you can get rid of. Lower RPM is similar as well, it doesnt have the snappy response of a well tuned carburated engine. I've just gotten used to it.
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Re: Very slow return to idle after full release of accelerator Any of you guys tune it with MAFT? I noticed mine doesn't do it since tuning it in ( close to 0 ltrims, between .880 and .900 o2's ). But I also have a 99 whereas your cam is different in the 01+02.
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TECH Senior Member
Joined: Nov 2001
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From: Troy, AL
Re: Very slow return to idle after full release of accelerator If there is no vacume leak and you've ensured that the throttle blade is fully returning, try doing the idle relearn procedure. Also, check to see what the IAC pintle position counts are at idle with the car fully warmed. They should never reach zero and really should be over 25 or so for a safe margin. A zeroed out IAC shouldn't be your problem or you'de have set a code by now.
Re: Very slow return to idle after full release of accelerator I don't think zeroed out iac counts are a problem at least on my m6.I drilled my tb out to 13/64 and flipped the idle screw on my tb and bumped idle just slightly and get no ses and the iac count does go to zero when I stop..idle is good and car runs fine..the iac counts increase again as I drive it of course.My idle does seem a bit slow to return maybe also..I did put in that newer
2000 tb cable when I changed out my 99 tb for a 2000 tb to get the faster cam on the 2000 and newer tbs..the stock 99 cable fit but was too short and made the throttle response really quick.
2000 tb cable when I changed out my 99 tb for a 2000 tb to get the faster cam on the 2000 and newer tbs..the stock 99 cable fit but was too short and made the throttle response really quick.
Thread Starter
Teching In
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From: California
Re: Very slow return to idle after full release of accelerator Thanks again for the input. Looks like I'll be in the garage this weekend doing some tweaking and tuning. ...not a bad place to be. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> I'm sure the answer is out there. I just hate hopping out of my 85 Berlinetta (carburated ZZ4, the perfect sleeper) with such awesome throttle response in to my 02 and feeling like someone put something all soft and cushy between me and my ride.
Banned
Joined: Nov 2001
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From: South Jersey
Re: Very slow return to idle after full release of accelerator Patman is right. It's called cat burn-off. It does that to burn off any extra fuel so the cats don't get clogged. But if it takes any longer than a few seconds than it's possible that there is a problem. But my '99 SS did it and my '02 WS6 does it. It sits around 1,100rpm then slowly drops back down to a normal idle. Hope this helps.
