How do I lower the engine idle speed?
Le Mans Master
Joined: Feb 2000
Posts: 7,032
Likes: 2
From: Newburgh NY
I would get two new IAC's from Autozone, NAPA,or somewhere. Don't muck them up or anything. Pull the olds ones out and adjust the pintle of the new ones to match the old ones (They should screw in and out to adjust). Once the depth is the same install them carefully.
If it works, done. If not, return them and get your money back.
If it works, done. If not, return them and get your money back.
Thread Starter
Intermediate
Joined: Dec 2008
Posts: 43
Likes: 1
Then I checked the timing, (yes, I unplugged the tan w/blk wire to do it) it was set high about 12*b, so i set it to 6*,
with that aluminum tube plugged idle is very low, with it hooked up to the air cleaner i'm getting an idle of about 950 to 1250 and sometimes i need to blip the throttle to get it to go down to 950ish, but that still seems a bit high.
Is vacuum on that tube normal?
Any ideas?
Thanks!
.
Thread Starter
Intermediate
Joined: Dec 2008
Posts: 43
Likes: 1
Anyone???
There is Vacuum suction on the 3/4" Diameter aluminum tube that comes out of the passenger side valve cover!, even when the PCV valve vacuum line on the other side's valve cover was removed, when i cap this alum tube the car idles close to what i think is normal.
Then I checked the timing, (yes, I unplugged the tan w/blk wire to do it) it was set high about 12*b, so i set it to 6*,
with that aluminum tube plugged idle is very low, with it hooked up to the air cleaner i'm getting an idle of about 950 to 1250 and sometimes i need to blip the throttle to get it to go down to 950ish, but that still seems a bit high.
Is vacuum on that tube normal?
Any ideas?
Thanks!
.
Then I checked the timing, (yes, I unplugged the tan w/blk wire to do it) it was set high about 12*b, so i set it to 6*,
with that aluminum tube plugged idle is very low, with it hooked up to the air cleaner i'm getting an idle of about 950 to 1250 and sometimes i need to blip the throttle to get it to go down to 950ish, but that still seems a bit high.
Is vacuum on that tube normal?
Any ideas?
Thanks!
.
Melting Slicks
Joined: Jul 2005
Posts: 2,740
Likes: 3
From: Aurora Ontario
You should go here and ask that question http://www.crossfire.homeip.net/
I don't remember. My car is stored for the winter. I don`t think there should be vaccum on that tube.
Have you check the EGR valve? Is it sealing. If you push up on the orfice the idle should change. If it doesn't its not working.
Do you still have the polution control stuff on the car? Those copper tubes in the exhaust manifolds all come together. Between them and the rubber hoses is a one way valve. There is one on each side. They go. Check them as well.
Jim
I don't remember. My car is stored for the winter. I don`t think there should be vaccum on that tube.
Have you check the EGR valve? Is it sealing. If you push up on the orfice the idle should change. If it doesn't its not working.
Do you still have the polution control stuff on the car? Those copper tubes in the exhaust manifolds all come together. Between them and the rubber hoses is a one way valve. There is one on each side. They go. Check them as well.
Jim
Last edited by jdp6000; Jan 17, 2009 at 11:27 AM.
Thread Starter
Intermediate
Joined: Dec 2008
Posts: 43
Likes: 1
Hi,
I checked that forum and like your car theirs too seem to be hibernating for the winter.
Where is the EGR orifice?
YES, this car seems to have all pollution controls in tact.
it is a CA car, but i think not much different than the other 49 state emission in 1982 Corvette.
What are the symptoms when the one-way valves 'go"?
Thank you!
I checked that forum and like your car theirs too seem to be hibernating for the winter.
Where is the EGR orifice?
YES, this car seems to have all pollution controls in tact.
it is a CA car, but i think not much different than the other 49 state emission in 1982 Corvette.
What are the symptoms when the one-way valves 'go"?
Thank you!
You should go here and ask that question http://www.crossfire.homeip.net/
I don't remember. My car is stored for the winter. I don`t think there should be vaccum on that tube.
Have you check the EGR valve? Is it sealing. If you push up on the orfice the idle should change. If it doesn't its not working.
Do you still have the polution control stuff on the car? Those copper tubes in the exhaust manifolds all come together. Between them and the rubber hoses is a one way valve. There is one on each side. They go. Check them as well.
Jim
I don't remember. My car is stored for the winter. I don`t think there should be vaccum on that tube.
Have you check the EGR valve? Is it sealing. If you push up on the orfice the idle should change. If it doesn't its not working.
Do you still have the polution control stuff on the car? Those copper tubes in the exhaust manifolds all come together. Between them and the rubber hoses is a one way valve. There is one on each side. They go. Check them as well.
Jim
Thread Starter
Intermediate
Joined: Dec 2008
Posts: 43
Likes: 1
with the engine running, when i push up from underneath on the EGR diaphram the engine slows down and runs rough,
is that normal?
thanks!
is that normal?
thanks!
You should go here and ask that question http://www.crossfire.homeip.net/
I don't remember. My car is stored for the winter. I don`t think there should be vaccum on that tube.
Have you check the EGR valve? Is it sealing. If you push up on the orfice the idle should change. If it doesn't its not working.
Do you still have the polution control stuff on the car? Those copper tubes in the exhaust manifolds all come together. Between them and the rubber hoses is a one way valve. There is one on each side. They go. Check them as well.
Jim
I don't remember. My car is stored for the winter. I don`t think there should be vaccum on that tube.
Have you check the EGR valve? Is it sealing. If you push up on the orfice the idle should change. If it doesn't its not working.
Do you still have the polution control stuff on the car? Those copper tubes in the exhaust manifolds all come together. Between them and the rubber hoses is a one way valve. There is one on each side. They go. Check them as well.
Jim
Le Mans Master
Joined: Apr 2001
Posts: 5,000
Likes: 1
From: Minneapolis, Mn USA
Whats your email address?
I have a pdf that covers CFI tune-up from the old CFI forum. Its better than this article and has some more tribal knowledge:
http://www.corvettefever.com/techart...ing/index.html
As far as vacuum in that line, it is pcv evacuation going to the air cleaner, so I dont have a good answer as to why covering this lowers your idle
I have a pdf that covers CFI tune-up from the old CFI forum. Its better than this article and has some more tribal knowledge:
http://www.corvettefever.com/techart...ing/index.html
As far as vacuum in that line, it is pcv evacuation going to the air cleaner, so I dont have a good answer as to why covering this lowers your idle
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Pro
Joined: Mar 2008
Posts: 716
Likes: 1
From: Albuquerque New Mexico
[QUOTE=MN-Brent;1568591276]Whats your email address?
I have a pdf that covers CFI tune-up from the old CFI forum. Its better than this article and has some more tribal knowledge:
http://www.corvettefever.com/techart...ing/index.html
Thanks for posting that link by the way - very nice read.
I have a pdf that covers CFI tune-up from the old CFI forum. Its better than this article and has some more tribal knowledge:
http://www.corvettefever.com/techart...ing/index.html
Thanks for posting that link by the way - very nice read.
Melting Slicks
Joined: Jul 2005
Posts: 2,740
Likes: 3
From: Aurora Ontario
Hi,
I checked that forum and like your car theirs too seem to be hibernating for the winter.
Where is the EGR orifice?
YES, this car seems to have all pollution controls in tact.
it is a CA car, but i think not much different than the other 49 state emission in 1982 Corvette.
What are the symptoms when the one-way valves 'go"?
Thank you!
I checked that forum and like your car theirs too seem to be hibernating for the winter.
Where is the EGR orifice?
YES, this car seems to have all pollution controls in tact.
it is a CA car, but i think not much different than the other 49 state emission in 1982 Corvette.
What are the symptoms when the one-way valves 'go"?
Thank you!
Have you messed with the throttle control screw on the front TBI? Is the weld broken? Its factory welded. If the weld is broken it may have been tampered with.
Its hard to figure this out over the net. Being there would make it easy. But its all we got...
5th Gear
Joined: Jun 2009
Posts: 5
Likes: 0
high idle
i have exactly the same problem. when i plug off the hose on the drivers side going into the bottom of the air cleaner the revs drop to normal ,thier is a strong vacuum presant. someone said that hose is to do with the pcv .if so ,why should it have such a strong vacuum ???
Melting Slicks
Joined: Jul 2005
Posts: 2,740
Likes: 3
From: Aurora Ontario
i have exactly the same problem. when i plug off the hose on the drivers side going into the bottom of the air cleaner the revs drop to normal ,thier is a strong vacuum presant. someone said that hose is to do with the pcv .if so ,why should it have such a strong vacuum ???
Follow the hose from the tbi. It plugs unto the temperture sensor bleeder valve. When the sensor reads 100 degrees it opens allowing the suction to open the door in the snorkel. Something on yours is not working. It could be the bleeder valve, the hose or hoses or the orfice.
Jim
Last edited by jdp6000; Jun 9, 2009 at 08:46 AM.
Melting Slicks
Joined: Jul 2005
Posts: 2,740
Likes: 3
From: Aurora Ontario
High ilde on an 82 is most always a vaccum leak. The ECM contols the idle. The ECM will loss the battle if the leak is too extreme. It will fight to lower the idle by adjusting the fuel/air mixture. The result is high unstable idle. The car will run rough.
Jim
Jim
Melting Slicks
Joined: Jul 2005
Posts: 2,740
Likes: 3
From: Aurora Ontario
Suction is not normal on that tube. Its a vent and should work in the reverse. It vents blowby from the rings. It should not be sucking. did you change the PCV as recommended?
You are going to have to replace the gasket on the top plate. The one the TBI's sit on. Change the TBI gaskets too. You really need to eliminate this as a source of vaccum leak. Otherwise you will chase this problem for ever.
Jim
You are going to have to replace the gasket on the top plate. The one the TBI's sit on. Change the TBI gaskets too. You really need to eliminate this as a source of vaccum leak. Otherwise you will chase this problem for ever.
Jim
Last edited by jdp6000; Jun 9, 2009 at 09:01 AM.
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
3/4" pass side tube
With the pcv valve pulled out of the drivers valve cover, there should be no vacuum in this tube. If anything, depending on the amount of engine blowby, and at higher rpm, you should have a slight bit of pressure.
With the pcv valve in place, you will see a slight vacuum at idle (5" or less).
Egr valve
Test this with a hand vacuum pump, opening it with vacuum will make the engine run very rough, smooth with no vacuum (egr closed).
You have a vacuum leak somewhere below the throttle plates, but my long distance diagnosis would be the intake to head gaskets.
Try the propane into the 3/4 pass side tube to confirm.
With the pcv valve pulled out of the drivers valve cover, there should be no vacuum in this tube. If anything, depending on the amount of engine blowby, and at higher rpm, you should have a slight bit of pressure.
With the pcv valve in place, you will see a slight vacuum at idle (5" or less).
Egr valve
Test this with a hand vacuum pump, opening it with vacuum will make the engine run very rough, smooth with no vacuum (egr closed).
You have a vacuum leak somewhere below the throttle plates, but my long distance diagnosis would be the intake to head gaskets.
Try the propane into the 3/4 pass side tube to confirm.
5th Gear
Joined: Jun 2009
Posts: 5
Likes: 0
i think you mean the smaller hose going to the snorkel at the front of the air cleaner? ime meaning the larger one that snakes up under and into a spout inside the air cleaner...it has a strong vacuum..when i plug it the idle lowers to a more normal rpm
5th Gear
Joined: Jun 2009
Posts: 5
Likes: 0
i think you mean the smaller hose going to the snorkel at the front of the air cleaner? ime meaning the larger one that snakes up under and into a spout inside the air cleaner...it has a strong vacuum..when i plug it the idle lowers to a more normal rpm