High idle won't go down

[BigBenb84]

Problem:
My idle has been perfect all summer. Just the other day I noticed my idle sitting at 1000 when at operating temp. If I turn the AC on it pulls it down to the 800ish normal level. I know how to adjust the idle screw and idle micro switch screws. So I back out the idle screw to lower the idle but it never goes down. I mean I look behind the arm and the screw isn't even touching the stop, its all the way closed. And at the same time the idle micro switch is closed so the idle motor can't even bring it down. I can't even push the arm anymore closed.

My guesses:
-Theres an air/vacuum leak. When cold it idles fine, even with the idle screw all the way out. I tried to listen but I don't hear any whistling. I should blow some cleaner/smoke in there to see what happens.
-Idle motor stops working when hot?

Someone please confirm...when you unplug an active idle speed motor it just stays in the position its in when you unplug it?

I had this problem like 2 years ago and adjusted the idle screw & micro switch positions and must have fixed it cause it wasn't a problem til the other day.

Whatya you guys think??

[DMCMW Dave]

Are the three brass screws closed?

A good quick test of the idle motor/ECU - with the engine running at idle, disconnect the plug on the idle ECU that is closer (of the two) to the center of the car. The engine should immediatly run up to about 2200 RPM. It should go right back to 775 when you plug it back in.

If it doesn't do that, the motor is sticky, ECU is bad, etc. If that test works, keep looking elsewhere.

To your original question - yes. When the motor is unplugged while running, typically nothing changes.

[BigBenb84]

Are the three brass screws closed?
Well I moved each about a 1/8 turn clockwise (hope thats what you meant) and the closest one to me broke off. I guess they were closed then, I just over tightened them. More like bolts then screws. The furthest one from me has green chalk(?) mark on it like how they do on ball joints sometimes to see if the nut is backing off. I'll start it tomorrow to see if it made a difference, its too late now.
6374

[Bitsyncmaster]

I had the same problem (but my bypass screws are fully closed). It turned out on mine to be the deceleration valves had crappy springs so they would open at closed throttle.

[DMCMW Dave]

Well I moved each about a 1/8 turn clockwise (hope thats what you meant) and the closest one to me broke off. I guess they were closed then, I just over tightened them. More like bolts then screws. The furthest one from me has green chalk(?) mark on it like how they do on ball joints sometimes to see if the nut is backing off. I'll start it tomorrow to see if it made a difference, its too late now.
6374

Oops - they are closed. Not a problem. Generally finger-tight will do it. They are supposed to break away like that to be "tamperproof" but the factory never broke them away. The only one that really matters is the one with the screwdriver slot - it cuts off both the other ones and is not a breakaway screw.

The two breakaway screws are the left and right bank idle bleeds, they feed into the third screw which controls both together.

[kings1527]

Problem:
My idle has been perfect all summer. Just the other day I noticed my idle sitting at 1000 when at operating temp. If I turn the AC on it pulls it down to the 800ish normal level. I know how to adjust the idle screw and idle micro switch screws. So I back out the idle screw to lower the idle but it never goes down. I mean I look behind the arm and the screw isn't even touching the stop, its all the way closed. And at the same time the idle micro switch is closed so the idle motor can't even bring it down. I can't even push the arm anymore closed.

My guesses:
-Theres an air/vacuum leak. When cold it idles fine, even with the idle screw all the way out. I tried to listen but I don't hear any whistling. I should blow some cleaner/smoke in there to see what happens.
-Idle motor stops working when hot?

Someone please confirm...when you unplug an active idle speed motor it just stays in the position its in when you unplug it?

I had this problem like 2 years ago and adjusted the idle screw & micro switch positions and must have fixed it cause it wasn't a problem til the other day.

Whatya you guys think??

Ben, did you solve this problem? What did it eventually turn out to be? I'm going through the exact same thing right now so any input would be invaluable. Thanks.

Alex

[BigBenb84]

Ben, did you solve this problem? What did it eventually turn out to be? I'm going through the exact same thing right now so any input would be invaluable. Thanks.

Alex


I unplugged my O2 sensor and now it idles as it should. I should replace it and then plug it back in but I hardly drive it and been busy. I was thinking maybe it was running really lean making the idle high?? I know unplugging it makes it default rich.

My gas mileage is about the same as it was before unplugging it but it has sooo much more power/throttle response now (thats the real reason I haven't plugged it back in I think :hihi2:) before it was sluggish to accelerate and quick blips of the throttle would produce hesitation for a second then feel the acceleration.

[TTait]

I had very high idle (2500 rpms) intermittently. Especially when hot. In my case the idle speed temp sensor in the valley was failing (but it could have also been the wiring to it or the ECU). If yours is only around 1000 rpms its probably either a misadjustment in the idle linkages, or if you have not messed with them, its probably a vacuum leak.

You can get some starting fluid and spray it around here and there in short shots all around the vacuum and air flow system - when ether gets sucked in the rpms will change.

[kings1527]

I had very high idle (2500 rpms) intermittently. Especially when hot. In my case the idle speed temp sensor in the valley was failing (but it could have also been the wiring to it or the ECU). If yours is only around 1000 rpms its probably either a misadjustment in the idle linkages, or if you have not messed with them, its probably a vacuum leak.

You can get some starting fluid and spray it around here and there in short shots all around the vacuum and air flow system - when ether gets sucked in the rpms will change.

Thanks TTait.

I tried a brand new ECU and that wasn't it. It's nice ruling things out. I think I really need to go over the vacuum lines and check for leaks.

Alex
6575

[Rokkinlen]

I had the same problem (but my bypass screws are fully closed). It turned out on mine to be the deceleration valves had crappy springs so they would open at closed throttle.

When you had this issue, did turning the AC on bring the rpm back down to normal? If so, what do the deceleration valve springs have to do with the AC compressor? Any ideas on how to troubleshoot?

TIA!

[Bitsyncmaster]

When you had this issue, did turning the AC on bring the rpm back down to normal? If so, what do the deceleration valve springs have to do with the AC compressor? Any ideas on how to troubleshoot?

TIA!

I don't recall. But any additional engine load would reduce idle RPM if your idle motor is already all the way closed.

[Ron]

When you had this issue, did turning the AC on bring the rpm back down to normal? If so, what do the deceleration valve springs have to do with the AC compressor? Any ideas on how to troubleshoot?

TIA!The deceleration springs are supposed to be closed at idle. If the springs are too weak or the valves are bad, extra air is allowed in. The system will increase the fuel to maintain the air-fuel ratio. If the ISM can not compensate for the extra air, you are left with a high RPM.

Remove the W pipe and inspect the valves and springs. The spring's coils should be uniform...

Left bad. Right, probably weak:
64402

Both bad:
64403