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i would like to know how can i raise de idle on my 3.1L engine, ive changed the pulley and the RPM dropped 200, from 800 to 600, i think i need to raise it because the alternator is not giving enough power to the battery,

plz help
 

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This is a question I have pondered over many a day. as of yet, i ahve not been able to figure out how to change the idle, I would suggest disconecting your battery and leaving it off for ten minutes... Just try it, it resets the computer.
 

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Which pulley did you change? The alternator pulley? To a larger or smaller one? If you changed it to a larger pulley to try and increase horsepower, you're pretty much screwed in terms of alternator output. Lost amp output at idle is common-knowledge amongst people who get an under-drive pulley. You can't "have your cake and eat it to" in this situation.

But, besides that, the ECM controls the idle, and there's really no way around it. If you had a scanner, you could see something called "DESIRED IDLE RPM" that is constantly being adjusted by the ECM via the IAC Valve based on the current engine temperature(the hotter, the lower the RPMs). You can try adjusting something called the "Idle Stop Screw", but it's HIGHLY recommended that you do NOT touch it!! Anyways, if you do adjust it, the ECM will just respond by lowering your IAC Counts, and therefore will lower the idle what it wants. So even adjusting this, which you shouldn't, really won't make any difference. The ECM is the commander-in-chief here.

So, in conclusion, the ONLY way that you could possibly do it is to get a PROM that is programmed to command a higher idle RPM at every engine(ECT) temperature. I'm not sure if they're available, but if you had a PROM programmer, it's extremely simple...
 

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I have the same problem. I have a deep bassy vibration in my car now, and the whole fuckin interior rattles. Can't you just adhust the throttle cable? Dunno. I just live with it. Roll down the windows :D and when she stalls, start er up again.
 

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Doesnt the 3.1 have an idle speed adjustment screw on the side of the throttle body? On alot of GM cars, the idle speed screw is covered up by an aluminum cap, which you just use an awl to poke a hole in and pop the cap out, and use an allen key to adjust the set screw. See if you can find something like that, cuz i dont have my car here right now to check. Im pretty sure there is one ....... now that i was reading on, GMRULZ4U, noted that that screw is the idle stop screw. figured i'd post this anyway.
 

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that idle speed screw is used in conjunction with the IAC valve...

when the factory setup your engine, they would tune it by checking the position of the IAC.. and if its not in the right spot, it would be compensated for by a slight adjustment of the idle speed stop screw..

if you try to adjust this screw, you will do nothing but wreck your IAC, ... so dont even bother trying.... like already stated.. the ecm ownz j00 lol

the chiltons repair manual gives a really good description as to how the entire system works, and how to setup a new IAC valve properly...
 
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