Low Idle after LC Header install
11-16-2021, 10:38 AM
#1
Low Idle after LC Header install
I have a 94 Toyota pickup with a 22RE. It has 250K miles and a 5 speed manual transmission. I Just installed an LC Engineering header on it, and after installation it idles very low and a little rough (500rpm when warm). I adjusted the idle screw as much as possible and got it to 750rpms which is still much lower than before the header install (11-1200rpms) and it's still a little rough. It idles at 1000rpms when cold and gets lower as it warms up, so I believe the IAC valve is functioning properly. I have no check engine light for the O2 sensor, so as far as I know it is functioning properly. Not sure what to check to try and fix this. Thanks for the help!
11-16-2021, 10:43 AM
#2
Also as a side note: The only thing I disconnected during the header install was two spark plugs. When I first started it back up, I realized I reconnected them in the wrong order and quickly fixed it. Not sure if I could have damaged something by having them connected in the wrong order.
11-16-2021, 11:32 AM
#3
Registered User
Did you check the air passages under the idle adjustment screw? Did you adjust the idle adjust screw, or the cover screw over it? Not that *I* ever did that...<ahem>...
Did you count the turns from the bottom the idle adjust was by screwing it all the way down, counting the turns as you go. Once it bottoms out, not tight just against the air passage, unscrew it all the way. Check it's o-ring. After all, how old is it? Rubber doesn't last forever, after all. It gets brittle eventual, and can fall apart. Not only does it allow too much air into the air passages, it can also clog one or both of them with little chunks of rubber.
Anywho, once the screw is all the way out, a short shot of carb cleaner into the two air passages is usually adequate to get them nice and clean. Replace the o-ring if required. They are readily available all over. A thin layer of Vaseline or silicon dielectric grease will make the o-ring last a lot longer, and make a better seal. Put the screw back in, screw it all the way to the bottom, and unscrew it to where it was when you started. It may not be right, but it's a starting point.
Set the idle RPMs, and then set the timing. I know, you already did, but cleaning out the air passages can have some effect on it. Then check the idle RPMs again. Should be about 750-850. If it's too high, the computer has a program in it that will cause the idle to drop way down, go back up high, drop way down, etc, as long as the brake pedal is pressed.
A short squirt of carb cleaner into the various vacuum ports can also have a beneficial effect.
Hope this is some kind of help for you.
Pat☺
Did you count the turns from the bottom the idle adjust was by screwing it all the way down, counting the turns as you go. Once it bottoms out, not tight just against the air passage, unscrew it all the way. Check it's o-ring. After all, how old is it? Rubber doesn't last forever, after all. It gets brittle eventual, and can fall apart. Not only does it allow too much air into the air passages, it can also clog one or both of them with little chunks of rubber.
Anywho, once the screw is all the way out, a short shot of carb cleaner into the two air passages is usually adequate to get them nice and clean. Replace the o-ring if required. They are readily available all over. A thin layer of Vaseline or silicon dielectric grease will make the o-ring last a lot longer, and make a better seal. Put the screw back in, screw it all the way to the bottom, and unscrew it to where it was when you started. It may not be right, but it's a starting point.
Set the idle RPMs, and then set the timing. I know, you already did, but cleaning out the air passages can have some effect on it. Then check the idle RPMs again. Should be about 750-850. If it's too high, the computer has a program in it that will cause the idle to drop way down, go back up high, drop way down, etc, as long as the brake pedal is pressed.
A short squirt of carb cleaner into the various vacuum ports can also have a beneficial effect.
Hope this is some kind of help for you.
Pat☺
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Dodgerfan (11-16-2021)
11-17-2021, 12:13 PM
#4
Registered User
Did you check the air passages under the idle adjustment screw? Did you adjust the idle adjust screw, or the cover screw over it? Not that *I* ever did that...<ahem>...
Did you count the turns from the bottom the idle adjust was by screwing it all the way down, counting the turns as you go. Once it bottoms out, not tight just against the air passage, unscrew it all the way. Check it's o-ring. After all, how old is it? Rubber doesn't last forever, after all. It gets brittle eventual, and can fall apart. Not only does it allow too much air into the air passages, it can also clog one or both of them with little chunks of rubber.
Anywho, once the screw is all the way out, a short shot of carb cleaner into the two air passages is usually adequate to get them nice and clean. Replace the o-ring if required. They are readily available all over. A thin layer of Vaseline or silicon dielectric grease will make the o-ring last a lot longer, and make a better seal. Put the screw back in, screw it all the way to the bottom, and unscrew it to where it was when you started. It may not be right, but it's a starting point.
Set the idle RPMs, and then set the timing. I know, you already did, but cleaning out the air passages can have some effect on it. Then check the idle RPMs again. Should be about 750-850. If it's too high, the computer has a program in it that will cause the idle to drop way down, go back up high, drop way down, etc, as long as the brake pedal is pressed.
A short squirt of carb cleaner into the various vacuum ports can also have a beneficial effect.
Hope this is some kind of help for you.
Pat☺
Did you count the turns from the bottom the idle adjust was by screwing it all the way down, counting the turns as you go. Once it bottoms out, not tight just against the air passage, unscrew it all the way. Check it's o-ring. After all, how old is it? Rubber doesn't last forever, after all. It gets brittle eventual, and can fall apart. Not only does it allow too much air into the air passages, it can also clog one or both of them with little chunks of rubber.
Anywho, once the screw is all the way out, a short shot of carb cleaner into the two air passages is usually adequate to get them nice and clean. Replace the o-ring if required. They are readily available all over. A thin layer of Vaseline or silicon dielectric grease will make the o-ring last a lot longer, and make a better seal. Put the screw back in, screw it all the way to the bottom, and unscrew it to where it was when you started. It may not be right, but it's a starting point.
Set the idle RPMs, and then set the timing. I know, you already did, but cleaning out the air passages can have some effect on it. Then check the idle RPMs again. Should be about 750-850. If it's too high, the computer has a program in it that will cause the idle to drop way down, go back up high, drop way down, etc, as long as the brake pedal is pressed.
A short squirt of carb cleaner into the various vacuum ports can also have a beneficial effect.
Hope this is some kind of help for you.
Pat☺
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