2 quick questions about settign base idle
Thread Starter
Racer
Joined: Dec 2004
Posts: 289
Likes: 3
From: new york
2 quick questions about settign base idle
89 here
I read that there is a punch out to get to the idle screw I assume this is it. below is a link to the picture.
http://s599.photobucket.com/user/gun...8d526.jpg.html
Depending on where I look I see tat it's best to unplug the timing connector. Can some one tel me if one of these 2 wires is it?
http://s599.photobucket.com/user/gun...tml?sort=3&o=0
My idle is a mess 'im at 1200-1300 in neutral and when i start the car. When starting from cold it's about 800 then climbs to 1300. If i am looking in the rite spot the idle screw has never been touched. I just changed my IAC
I read that there is a punch out to get to the idle screw I assume this is it. below is a link to the picture.
http://s599.photobucket.com/user/gun...8d526.jpg.html
Depending on where I look I see tat it's best to unplug the timing connector. Can some one tel me if one of these 2 wires is it?
http://s599.photobucket.com/user/gun...tml?sort=3&o=0
My idle is a mess 'im at 1200-1300 in neutral and when i start the car. When starting from cold it's about 800 then climbs to 1300. If i am looking in the rite spot the idle screw has never been touched. I just changed my IAC
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
Don't mess with the idle screw.....don't punch out the cover on the screw. Your idle is controlled by the IAC valve at the base of the TB.
If the picture you have circled and labeled as #1 is a SINGLE wire then that is it. Unplug the wire. I usually find the mark on the balancer and use something like paper white out to paint the slot in the balancer so it shows up with the timing light. Loosen the bolt on the distributor so you can turn it. Attach the timing light to the battery and be careful where the cords off the light are....don't want to get them into the belt!!!
. Start the engine and use the light to align your marks by turning the distributor. Tighten down the distributor when you have it set....recheck with your light to be sure it didn't move.
You will set a code 44 when you unplugged the single wire. Turn off the car and disconnect the negative battery cable for about 30 seconds. This will erase any codes and turn off the check engine light. You are ready to go.
To replace the IAC you will have to remove the TB, so get gaskets. Clean the TB while it is off.
Good luck.
If the picture you have circled and labeled as #1 is a SINGLE wire then that is it. Unplug the wire. I usually find the mark on the balancer and use something like paper white out to paint the slot in the balancer so it shows up with the timing light. Loosen the bolt on the distributor so you can turn it. Attach the timing light to the battery and be careful where the cords off the light are....don't want to get them into the belt!!!
. Start the engine and use the light to align your marks by turning the distributor. Tighten down the distributor when you have it set....recheck with your light to be sure it didn't move.You will set a code 44 when you unplugged the single wire. Turn off the car and disconnect the negative battery cable for about 30 seconds. This will erase any codes and turn off the check engine light. You are ready to go.
To replace the IAC you will have to remove the TB, so get gaskets. Clean the TB while it is off.
Good luck.
Melting Slicks
Joined: Sep 2008
Posts: 2,376
Likes: 111
From: Cherokee National Forest TN
Remove the base idle plug.
Connect a paper clip, to your diagnostic terminal under your dash connect to terminal A and B (the top right two pins).
Turn on ignition but don't run the engine.
wait at least 30 seconds and then remove the idle air valve connector (IAC) (the square plug) then turn off ignition and unplug the paperclip.
Now remove the timing connector a single wire near the fuel pump relay.
Start your vette and set the idle speed to 400 rpm in neutral (auto trans) 450 rpm (manual trans) then check your throttle position sensor,
the top two wires it should be set to 0.54volts dc, also confirm with engine off that the tps rises to 4.5 volts at full throttle.
Turn off the ignition and reconnect the iac valve connector and timing connecter and start your vette.
it should go to 1200 rpm then drop slowly to 600 rpm, take the car for a 15 minute drive with the usual stop lights.
It is normal for a little hunting while the ecm relearns, also do a few spirited take offs.
All should settle after 15 to 30 mins normal driving and have a stable idle.
http://www.batee.com/corvette/dcrg/r...scuss_sim5.htm
Connect a paper clip, to your diagnostic terminal under your dash connect to terminal A and B (the top right two pins).
Turn on ignition but don't run the engine.
wait at least 30 seconds and then remove the idle air valve connector (IAC) (the square plug) then turn off ignition and unplug the paperclip.
Now remove the timing connector a single wire near the fuel pump relay.
Start your vette and set the idle speed to 400 rpm in neutral (auto trans) 450 rpm (manual trans) then check your throttle position sensor,
the top two wires it should be set to 0.54volts dc, also confirm with engine off that the tps rises to 4.5 volts at full throttle.
Turn off the ignition and reconnect the iac valve connector and timing connecter and start your vette.
it should go to 1200 rpm then drop slowly to 600 rpm, take the car for a 15 minute drive with the usual stop lights.
It is normal for a little hunting while the ecm relearns, also do a few spirited take offs.
All should settle after 15 to 30 mins normal driving and have a stable idle.
http://www.batee.com/corvette/dcrg/r...scuss_sim5.htm
Race Director
Joined: Sep 2003
Posts: 16,838
Likes: 341
From: Database Error Indiana
The tan wire with the black stripe is the one for timing. The other one is your wipers. If you turn the idle screw, you need to set the TPS also. 
Sounds like you may have a vacuum leak or a worn throttle shaft though.
Sounds like you may have a vacuum leak or a worn throttle shaft though.
Thread Starter
Racer
Joined: Dec 2004
Posts: 289
Likes: 3
From: new york
Thanks, that's what I thought it was. I am going to to do the entire process TPS included as stated in FSM and posted by churchkey. I don't belivve I have any vacuum leaks, I had 1 and fixed it. I did just replace my IAC I am sure the base idle needs to be set. Most likely the TPS is not set to .54 volts. As I have had the TB off the car 2x in last week.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
The TPS comes off with the throttle body so removing the throttle body won't affect it.
I never touched the idle screw because my car is totally stock. Then it started dying at stops. The fix was to do the minimum idle adjustment. My theory is that the linkage bends over time and allows it to go out of adjustment.
High and/or wandering idle is almost always a vacuum leak. There are some pretty subtle vacuum connections (EGR valve sticking/stuck open?) so don't be so sure you have found them all. My car had a vacuum leak where the PCV tube connects to the intake manifold. I HEARD that one because it made a weird noise when the engine got hot and the rubber hose became flexible.
I never touched the idle screw because my car is totally stock. Then it started dying at stops. The fix was to do the minimum idle adjustment. My theory is that the linkage bends over time and allows it to go out of adjustment.
High and/or wandering idle is almost always a vacuum leak. There are some pretty subtle vacuum connections (EGR valve sticking/stuck open?) so don't be so sure you have found them all. My car had a vacuum leak where the PCV tube connects to the intake manifold. I HEARD that one because it made a weird noise when the engine got hot and the rubber hose became flexible.
Team Owner
Joined: Jul 2004
Posts: 28,472
Likes: 3,290
From: Hartford WI
I'd also check and clean the injectors if it hasn't been done in a long while.
Team Owner
Joined: Jul 2004
Posts: 28,472
Likes: 3,290
From: Hartford WI
Thanks, that's what I thought it was. I am going to to do the entire process TPS included as stated in FSM and posted by churchkey. I don't belivve I have any vacuum leaks, I had 1 and fixed it. I did just replace my IAC I am sure the base idle needs to be set. Most likely the TPS is not set to .54 volts. As I have had the TB off the car 2x in last week.
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Team Owner
Joined: Jul 2004
Posts: 28,472
Likes: 3,290
From: Hartford WI
The fix was to do the minimum idle adjustment. My theory is that the linkage bends over time and allows it to go out of adjustment.
High and/or wandering idle is almost always a vacuum leak. There are some pretty subtle vacuum connections (EGR valve sticking/stuck open?) so don't be so sure you have found them all. My car had a vacuum leak where the PCV tube connects to the intake manifold. I HEARD that one because it made a weird noise when the engine got hot and the rubber hose became flexible.
High and/or wandering idle is almost always a vacuum leak. There are some pretty subtle vacuum connections (EGR valve sticking/stuck open?) so don't be so sure you have found them all. My car had a vacuum leak where the PCV tube connects to the intake manifold. I HEARD that one because it made a weird noise when the engine got hot and the rubber hose became flexible.
Thread Starter
Racer
Joined: Dec 2004
Posts: 289
Likes: 3
From: new york
OOO hell yea, I just did intake gaskets. i cleaned the hell out of runners plenum tb everything all new gaskets. I just did the process idle is still high about 900 in neutral I have a 6 speed. TPS was at .46. I only drove it a few minutes i have to go out in ab it so i will be going on a 20 mile drive. i will check for vacuum leaks again. I recently fixed vacuum line from the EGR, i will check to make sure it is intact.
Last edited by guno89; Mar 30, 2013 at 03:41 PM.
Team Owner
Joined: Jul 2004
Posts: 28,472
Likes: 3,290
From: Hartford WI
OOO hell yea, I just did intake gaskets. i cleaned the hell out of runners plenum tb everything all new gaskets. I just did the process idle is still high about 900 in neutral I have a 6 speed. TPS was at .46. I only drove it a few minutes i have to go out in ab it so i will be going on a 20 mile drive. i will check for vacuum leaks again. I recently fixed on from the EGR i will check to make sure it is intact.
Take a propane torch WITHOUT THE FLAME and NO SMOKING to the hhoses and mating surfaces.
How do you know the idle is at 900? Not trying to be a smartass but the tach is usually off in a Vette. Did you do it via ALDL or use a timing light with tach? I did all 3 and according to the ALDL and the timing light, it is 300-400 RPM lower than what the tach says.
Thread Starter
Racer
Joined: Dec 2004
Posts: 289
Likes: 3
From: new york
I believe the TPS is at 0.54.
Take a propane torch WITHOUT THE FLAME and NO SMOKING to the hhoses and mating surfaces.
How do you know the idle is at 900? Not trying to be a smartass but the tach is usually off in a Vette. Did you do it via ALDL or use a timing light with tach? I did all 3 and according to the ALDL and the timing light, it is 300-400 RPM lower than what the tach says.
Take a propane torch WITHOUT THE FLAME and NO SMOKING to the hhoses and mating surfaces.
How do you know the idle is at 900? Not trying to be a smartass but the tach is usually off in a Vette. Did you do it via ALDL or use a timing light with tach? I did all 3 and according to the ALDL and the timing light, it is 300-400 RPM lower than what the tach says.
I did it via ALDL, yes I was going by the tach. After driving a bit when I am in neutral I fluxuate between 800-900, i think 700 is normal if I remember correctly. None the less the car runs way better now and has a much better response when hitting the gas. I have a timing light I will test with that tomorrow.
Team Owner
Joined: Jul 2004
Posts: 28,472
Likes: 3,290
From: Hartford WI
TPS is supposed to be at 0.54 I was at 0.46 I am now at .054
I did it via ALDL, yes I was going by the tach. After driving a bit when I am in neutral I fluxuate between 800-900, i think 700 is normal if I remember correctly. None the less the car runs way better now and has a much better response when hitting the gas. I have a timing light I will test with that tomorrow.
I did it via ALDL, yes I was going by the tach. After driving a bit when I am in neutral I fluxuate between 800-900, i think 700 is normal if I remember correctly. None the less the car runs way better now and has a much better response when hitting the gas. I have a timing light I will test with that tomorrow.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
99.99% of the time a wandering idle is caused by a vacuum leak. They can be very subtle and in non-obvious places. A stuck/sticking EGR valve will do it, for example.
Advanced
Joined: Jan 2001
Posts: 65
Likes: 0
From: eau claire, wi. usa
I used the procedure in tech tips by Lars, he outlines the process very well and started that the process is in the FSM only it's in about 3 different sections of the manual. You can print the procedure and take out to the car for quick reference. You should have good results.