idiling at 650-750
- Thread starter dpkeefe11
- Start date
WTF? The ECU controls the IACV based on the programmed target idle speed versus coolant temp and the actual engine rpm measured.
It is but only to shut the thing off. The idle strategy operates as 3p says except he is no doubt deliberately simplifying it. In a nutshell the ECU is programmed with a set of target idle speeds for various conditions. By monitoring engine rpm it steps the valve open or closed until the current target is met. It's nothing more than your basic output drives process variable to match setpoint feedback loop except the set points vary and even ramp at times. The valve drivers are disabled when the engine is off idle and vehicle speed exceeds 11 mph. There's a bit more to it but 'dems the basics.
Yup, that's it in a nutshell but the idle program is actually very complicated with learned values stored for the IACV. Lots of inputs including IDL, NSW, DFG, and AC all playing a role in the target idle speed, not to mention high coolant temp and low oil pressure.
Well, his question still needed to be answered although a quick look at the TEWD would have done it.
While I'm here an interesting thing about AC idle up is the use of timing advance to prevent rpm sag while the valve is stepping. Iirc it's the only idle up function that does this.
While I'm here an interesting thing about AC idle up is the use of timing advance to prevent rpm sag while the valve is stepping. Iirc it's the only idle up function that does this.
I did look at tsrm, but it's only shows you how to test it and r&i. The reason I'm asking is because lately my idle has been surging from 400-800rpm with it dying out at times. At first I thought it was my map ecu tune, so I unplugged it and went back to the lex afm to rule that out. Still surging and dying. I keep hearing a hissing sound around the intake pipe come a go. The hissing goes right along with the idle going up and down. I took off the intercooler pipes and inspected all couplers for leaks. I then realized that it was coming from the pipe that goes from the IAC to the intake pipe pre turbo. I don't know why, but it keeps opening and closing after the car is at normal operating temperature. I did remove and replace the oring on the CPS, but I was having this problem before I did that. It just randomly started happening. I'm about to go to the garage and put power to it and test it out. I think it might be time to replace it. We'll see.
Suprapowaz!(2);1945963 said:
Are the wires to it still intact? I'm not sure if it does but it could be jumping a step. Instead of settling where it wants, it's bouncing back and forth to try and keep the ecu happy.
No, I took it out of the manifold to test it. I put + power to B1 & B2. I then touched S1-S2-S3-S4-S1,and S4-S3-S2-S1-S4 in that sequence. I can hear is click very faintly, but the piston doesn't move. I could still blow air through it. It does not close. It's stuck in the open position.
I need to look for a good one. I'll have to get with a friend with a known good IAC and test his then mine back to back to compare them.
I need to look for a good one. I'll have to get with a friend with a known good IAC and test his then mine back to back to compare them.
Take it apart and test it. See if the pintle moves or if the bearings are frozen. That said if stuck it's not the source of your surging. Remember, unplugging even a good ISCV simply freezes it in place. Thereafter any large changes in idle obviously can't be valve related.
And I said the TEWD. It clearly shows the ISCV being connected directly to the ECU. That idle is controlled by the ECU (along with spark advance) is by definition what makes this a TCCS. If that's not what you meant by "what controls the IAC valve?" I stand corrected.
And I said the TEWD. It clearly shows the ISCV being connected directly to the ECU. That idle is controlled by the ECU (along with spark advance) is by definition what makes this a TCCS. If that's not what you meant by "what controls the IAC valve?" I stand corrected.
Just unplug it. If its caused by the IACV hunting your idle will steady out. Somehow I doubt that's your problem though.
(JJ beat me to the punch!)
(JJ beat me to the punch!)
Great minds think alike. Why such an obvious conclusion about the valve needs great minds is a mystery 
Yeah, that's what I was asking. I'll take it apart and see what's going on inside.
If my timing is off will the ecu make the iscv open and close at idle like that? It is possible that I didn't put the CPS back in exactly where it's supposed to be. I did put the crank at 0 with the piston at the top, and mark the cps before I pulled it.
If my timing is off will the ecu make the iscv open and close at idle like that? It is possible that I didn't put the CPS back in exactly where it's supposed to be. I did put the crank at 0 with the piston at the top, and mark the cps before I pulled it.
It's off the car, and I've already took it apart. The inner workings move freely.
I tried to upload a vid, but having problems with this camera. Will use the camcorder and upload a vid when I get back home. I have to run an errand.
I tried to upload a vid, but having problems with this camera. Will use the camcorder and upload a vid when I get back home. I have to run an errand.
[video=youtube;sWBI4fqCEDc]http://www.youtube.com/watch?v=sWBI4fqCEDc&feature=youtu.be[/video]
I'm going to test it again to see if it moves up and down. I'll them put it back on my car and when my idle begins to surge I'll unplug it to see if it continues to idle funny or not.
I'm going to test it again to see if it moves up and down. I'll them put it back on my car and when my idle begins to surge I'll unplug it to see if it continues to idle funny or not.
Ok, I re-tested the ISCV and it still didn't move up or down.
3p, you were right. Unplugging the the ISCV did nothing different to the idle lope. It still did it.
The idle loping from 400-800 has mellowed out some. Still lopes a little but not as bad as before.
I'm going to my friends shop to use his timing light to make sure it's dead on. Then I'm going to change the plugs since they been in there for roughly 5000 miles. They're Autolite 3922 coppers gapped to 0.028. I pulled them out recently to check their condition and two of them wore down to 0.035 gap. They all looked black from running rich the last hundred miles or so. I was doing some street tuning with the map ecu and was running rich until I could dial it in.
Would hurt to do a compression test while I'll have the plugs out. Just for peace of mind.
This camcorder takes crappy vids. Half the time it's out of focus.
[video=youtube;XNNv1XTjoXs]http://www.youtube.com/watch?v=XNNv1XTjoXs&feature=youtu.be[/video]
BTW, when I unplugged the map ecu and went back to the lex afm set up I pulled the main ecu relay to reset it. I haven't took the car out for a good long drive for the ecu to relearn stuff. I only took it around the block a couple of times to readjust the lex afm screw and afpr to "normal" cruising/idle behavior. I just don't want to take it out that far until the idling issue was fixed.
3p, you were right. Unplugging the the ISCV did nothing different to the idle lope. It still did it.
The idle loping from 400-800 has mellowed out some. Still lopes a little but not as bad as before.
I'm going to my friends shop to use his timing light to make sure it's dead on. Then I'm going to change the plugs since they been in there for roughly 5000 miles. They're Autolite 3922 coppers gapped to 0.028. I pulled them out recently to check their condition and two of them wore down to 0.035 gap. They all looked black from running rich the last hundred miles or so. I was doing some street tuning with the map ecu and was running rich until I could dial it in.
Would hurt to do a compression test while I'll have the plugs out. Just for peace of mind.
This camcorder takes crappy vids. Half the time it's out of focus.
[video=youtube;XNNv1XTjoXs]http://www.youtube.com/watch?v=XNNv1XTjoXs&feature=youtu.be[/video]
BTW, when I unplugged the map ecu and went back to the lex afm set up I pulled the main ecu relay to reset it. I haven't took the car out for a good long drive for the ecu to relearn stuff. I only took it around the block a couple of times to readjust the lex afm screw and afpr to "normal" cruising/idle behavior. I just don't want to take it out that far until the idling issue was fixed.