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M

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Discussion Starter #1
Reading in a manual it say there is no adjustment. I would like to bring it down a bit because it like to take off when in gear. If I bump it in neutral it takes significantly less breaking power to stop then if I am in gear. I does not like to come down under 1K for a few seconds after stopping.

Any thoughts?
 
S

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Discussion Starter #2
Mark,
If I'm not mistaken (I'm new to this) the pcm controls the idle. Perhaps someone like Bryan (who is awesome to work with) could do something for you. I know recently I had a problem with mine idling too low (would stall at lights while in gear) and it was a matter of just removing the IAC motor and cleaning it. Hope this helps.
 
J

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My 94 ISS idle speed has always been too high but I think that is normal. I have read here and other LT1 sources say they have to keep their foot firmly planted on the brake at stoplights. This brings up another problem. I sometimes put my car in Park at stop lights to avoid this 'Hold the car back with the brakes'. The problem with the 'put it in Park until the light turns green' is -when it does turn green and you drop it in 'Drive' and depress the accelerator to go, the slow as molasses 4L60E doesn't engage quickly enough and it as though you rev'ed the engine and dropped it into Drive.A neutral drop! Not good for the trans. Anyone else have this problem?
 
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Discussion Starter #6
The strong pull at idle is at least in part due to the very low stall speed of the stock TC. And the reason the engine does not just completely shut down to a 550rpm idle when you lift your foot is so that it still revs high enough to produce vacuum to operate the brakes. All this can be adjusted in the pcm by any competent custom tuner, just a few of the many ways custom pcm works makes the car more "drivable". I would also look for a dirty IAC of just TB in gerneral.
 
L

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Discussion Starter #7
Yes, first thing you want to do is remove the Throttle Body & spray clean[Carb Cleaner] throttle blades/shaft. Also, while TB is off, remove Idle Air Control(IAC)[2 T-25? Torx screws], located underside of TB, and spray clean IAC pintle & passages.
Buy a TB/Intake Manifold gasket, incase it breaks on TB removal; Fel-Pro# 60655.
This should be standard maintenance every 25K or so!
 
M

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Discussion Starter #8
A VERY important thing to remember to do when you do a thorough cleaning/R&R on the TB like that is to hook the car up to a scan tool afterwords. Get it fully warmed up (go take it a few exits up the highway, and back, then drive around town a bit...make sure the oil is warmed up and all) then make sure that at idle in park or neutral, now look at the scantool and make sure the IAC counts are around 20-30 to hold a steady idle...too low is bad and too high can be bad also.

Since you're going to have the TB off, I recommend taking out the set screw and reversing it. This way it is 100% accessible from the front of the engine without removing the TB again. Make sure you have a scan tool before you touch it though. If your IAC counts are too high, you want to turn the stop screw to open the throttle blades up a bit, if they're too low, you want to close it. Either way you should also check for vacuum leaks everywhere as they will affect the IAC and idle. A lot of guys have found that to avoid having the TB blades excessively open (usually with big heads or cams) that they need to drill out the hole in the center of the TB to be a slightly larger diameter...on a stock engine you shouldn't have to touch it though.
 
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Discussion Starter #9
Cleaning the TB on an LT1 is an important routine maintenance procedure. I also recommend you remove the passenger side hose from the valve cover to the TB to reduce the amount of build up behind the TB plates. Replace the valve cover opening with a plug in air filter. I know this is a controversial procedure. It works.
 
M

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Discussion Starter #10
Thanks for the info. Will do some cleaning this weekend.
 
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Discussion Starter #11
skaufman, I am new to this forum and somewhat less knowlegable. I have a 95 ss impala and am experiencing the idling problem similar to the post you made to Mark. In addition to stalling at lights, mine is starting to just go dead ( completely cut off). You made mention to removing the IAC motor? and cleaning it to resolve your problem. How is this done? Where is the IAC motor?
 

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My 94 ISS idle speed has always been too high but I think that is normal. I have read here and other LT1 sources say they have to keep their foot firmly planted on the brake at stoplights. This brings up another problem. I sometimes put my car in Park at stop lights to avoid this 'Hold the car back with the brakes'. The problem with the 'put it in Park until the light turns green' is -when it does turn green and you drop it in 'Drive' and depress the accelerator to go, the slow as molasses 4L60E doesn't engage quickly enough and it as though you rev'ed the engine and dropped it into Drive.A neutral drop! Not good for the trans. Anyone else have this problem?
My 94 ISS idle speed has always been too high but I think that is normal. I have read here and other LT1 sources say they have to keep their foot firmly planted on the brake at stoplights. This brings up another problem. I sometimes put my car in Park at stop lights to avoid this 'Hold the car back with the brakes'. The problem with the 'put it in Park until the light turns green' is -when it does turn green and you drop it in 'Drive' and depress the accelerator to go, the slow as molasses 4L60E doesn't engage quickly enough and it as though you rev'ed the engine and dropped it into Drive.A neutral drop! Not good for the trans. Anyone else have this problem?
I have the same transmission problem with my 06 impala
 

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I put mine into neutral at some stoplights and sometimes when I shift it into drive again, I press the accelerator and there is a loud slam in the transmission, and it won't accelerate, but when I let off and try again, it shifts into gear fine. I think the gear issue is a problem with you shifting it into gear and pressing the pedal too quick. Often times, that is my problem
 

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We're sure in the midst of another infestation of new posters all with issues for every car out there EXCEPT ours. It would be downright fascinating to find out exactly how they're getting herded over here.

And how in the ever-loving F do they manage to all tag on to 16-year old dead threads? Downright fascinating.
 

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Hey, they use the search function, so let's celebrate that.

For the FWD 00-up impalas, there was a known issue with pullaway clunk, especially if you're hard on the gas. Low fluid level is the first culprit, transmission problems is the next one.

For the '94-96 Impalas / Caprices / Roadmasters / Etc, yes, the tight torque converter causes a lot of this. You can bump idle speed down a little but most of these cars hot idle in gear at 550 and if you go below that you start running into low oil pressure and lack of alternator charging.
 
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