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Discussion Starter · #1 ·
on start up my iac reads as high as 30 but once the car warms up they drop to 0 and i get a real bad iidle, what would cause them to drop when warmed up?? and if adjusted would that help my idle??.........thanks
 

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it may help...get it in specs and see..15-30 warm idle
 

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The reason It drops is because the car is warmed up. The IAC number tells you how far open the throttle is to maintain idle. It needs more air when the engines cold. Since you're is reading 0, that means that the engine is finding it's own air somewhere. If all your vacuum areas are tight, then the throttle blade is just open too far.
You need to close off the throttle blade untill you're IAC come up into spec. Keep in mind that's going to be a balancing act because as you back off on the "idle screw" your TPS readings are going to go down. (also, when you first turn on the key the ECM looks at the TPS and remembers that as the idle number. You'll be doing alot of on and off with the engine too)
Once you get the engine warm, the IAC in speck and the TPS put back, then you'll be set up to see if anything is really out of whack.
 

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go to my site, click on basics and read the sections on iac and tps...follow the instructions :)
 

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I'm troubleshooting something similar with idle and 0 iac counts when warm with a car I recently picked up. I noticed two things I am hoping someone might be able to shed some light on. First is on the throttle body, on the passenger side is what appears to be a vacuum source that is wide open. Does anyone have any idea what this might be and why someone would just leave it open? I can send in a picture if necessary to see it. The second is the valve on the passenger side valve cover. This also appears to look like a vacuum send and receive and both are wide open. Does anyone have any information on what this is and also why someone might just leave both of these open? Any information and or suggestions are greatly appreciated. :headbang:
 

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The ports on the tb are water ports for connection to the heater lines...to supply warming to the tb in order to improve drivability in very cold weather. Most of us disconnected the supply years ago in the hope that it would make more power by allowing cooler air. Most of us now believe this was a myth, but, we suffered no loss in drivability so we did not bother to reconnect them.

The wastegate solenoid is mounted on the end of the passenger valve cover. One port was open, and, the other went to the factory boost control plumbing. Sounds like yours has been plumbed directly to use the wastegate rod as the boost control solely rather than the factory "Y".
 

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Discussion Starter · #7 ·
ok i found my tps and understand how to adjust it, but the iac i found it but can't find where the screw is to set it?????????? help
 

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The idle adjusting screw is on the drivers side of the throttle body. Adjust your idle to within specs and then re-adjust your tps to specs. Takes some playing with back and forth but it's easy.
 

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Discussion Starter · #9 ·
ok i found a phiilips head screw like right behind the tps its the only srew i see on the drivers side that must be it, i checked it it and it was tight so i turned it just a bit counter clockwise and it apears the srew has no tension on it, if thats the case won't it viberate looser???
 

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The screw should have a little spring on it which maintains tension. Here's a picture.
 

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The idle speed set screw will have enough tension on it where it will not vibrate loose. Do you have an after market tach or a scantool to set idle rpm's. The factory tach sucks.
 

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mgjbbc said:
ok i found a phiilips head screw like right behind the tps its the only srew i see on the drivers side that must be it, i checked it it and it was tight so i turned it just a bit counter clockwise and it apears the srew has no tension on it, if thats the case won't it viberate looser???
Screw is on driver side, across from TPS. Large headed torq head, it screw thru the TB to a throttle plate. If you ever worked on a carb it would be the idle screw..
HTH
Jim
 

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Discussion Starter · #13 ·
ok thanks for the picture i found it, i know you all said drivers side but i was looking on the passengers side the whole time ever sence the brain surgery i get real confused some times, hope this helps as my goal this year is to drive more than last years 288 miles........thanks again for the help
 

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turbojd said:
Do you have an after market tach or a scantool to set idle rpm's. The factory tach sucks.

That screw won't change the idle speed (unless you go waaaaaay out of spec). It's there to set the amount of air bleed past the throttle blade to just below the amount the engine needs to idle. Then the chip sets the speed with additional air through the IAC.
 

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yeah like earl said- unless your way out it wont mess you up- you have to be within a certain perameter so the computer can adjust it with

but he said hes reading 0 at idle so that would mean its closing the IAC all the way due to the throttle being too far open correct?
 

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It means the blade is being opened such that the air is allowed to bypass the iac passages and the idle is being controlled by the blade instead.

The iac screw needs to be turned ccw until counts come up. The tps voltage will drop, but, given the width of the window, may not need to be readjusted.

The iac range is not nearly as many believe. Anywhere from 10-40 counts may not make a difference on many cars. :)
 
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