[yellow1098]

I have been having a hanging idle issue when the car is warm after just normal driving. I have it set at 950 at idle and at about 95% of the time it bounces from about 1,200-1,350 in gear. When I put it in park or neutral it gets all the way up to 1,500-1,600.

The IAC at Idle still shows 0 even though the idle is super high. Also, at a light if I put it in neutral and wack the throttle it will drop it down from that 12-1300 to about 1,100. Not sure why that affects it.

I am running a Wilson 1,200 cfm throttle body and have checked the blades multiple times and they seem to all the way closed. I am also running a 1 inch spacer under the throttle is that has any effect.

If anyone has any suggestions or can point me in the right direction I would appreciate it.

[RocktimusPryme]

Originally Posted by yellow1098

I have been having a hanging idle issue when the car is warm after just normal driving. I have it set at 950 at idle and at about 95% of the time it bounces from about 1,200-1,350 in gear. When I put it in park or neutral it gets all the way up to 1,500-1,600.

The IAC at Idle still shows 0 even though the idle is super high. Also, at a light if I put it in neutral and wack the throttle it will drop it down from that 12-1300 to about 1,100. Not sure why that affects it.

I am running a Wilson 1,200 cfm throttle body and have checked the blades multiple times and they seem to all the way closed. I am also running a 1 inch spacer under the throttle is that has any effect.

If anyone has any suggestions or can point me in the right direction I would appreciate it.

I actually fought a similar issue for a while with my Terminator X. It was intermittent; sometimes I could feel the car fighting me while I tried to brake when I was cruising. After searching my butt off for vacuum leaks and whatnot I broke down and asked the guys as EFISystemspro

They said it was somewhat common if you have a normal variable PCV valve in your system. I did a short youtube video about it. Switched to the metered LS style PCV valve and have not had the problem anymore.

https://youtu.be/nTkxtj29BtY

[yellow1098]

Wow that was an awesome video! Thank you so much! That sounds exactly like what I have going on with my system!

Buttttt let me throw alittle curveball question about my setup…I am not running a PCV valve or any breathers…I have a Moroso vacuum pump to a catch can coming from my passenger side valve cover. Any idea how that would play into the situation?

Also, it seems to pulling more oil and vapors into the catch than it seems it should be.

Other than this situation the engine runs amazing, lots of power, no smoke, great pressure …..thanks again!

[RocktimusPryme]

Thank you.

I cant say for sure, because Ive never ran a vacuum setup like that. But I think we are on the right track. Maybe when the relief valve activates or something like that, its triggering your system to start acting odd, just like a variable PCV was for mine.

I dont know if there are different orifice types available, or maybe adjusting your existing vacuum system so its at a higher pressure (Or lower) maybe it will be less sensitive? I would have thought you would still need a port for fresh air somewhere. Ill try to find some information on plumbing those systems later and see what we can come up with.

First thing I think I would do on your end is look up if you plumb a vacuum pump for a carbed system and an LS system the same way. If you would generally do it differently for the fuel injected setup I would do that. Because that was my fix. The LS engines wanted a fixed meter PCV vs the floating ball types used in classic cars.

[yellow1098]

I will definitely look that up to see where that takes me about the LS vs the carb setup….and like your thought on why wouldn’t I need to let fresh air in somewhere….since my whole setup is from butler maybe they would have an answer to that one as they run a lot of these vaccum pump setups on there engines ….thank you so much for your help and info

[yellow1098]

I actually think I might try your setup even though Im running the vaccum pump to see if that fixes it…for the money…can’t hurt

[Dlaw455]

I am running the terminator x with wilson 4500 throttle body setup and a vacuum. Pump so its somewhat similar to yours.. you need the IAC to be around 5-10% at idle. Otherwise it can't drop the idle any lower if it's already at 0. You either have the primary or secondary blades open too much, a vac leak or incorrect timing. First make sure the secondary adjuster screw is backed out as that will increase idle and not as easy to check as the primary screw. What's your MAP at idle? 60kpa for ex?

[yellow1098]

I am running the exact same throttle body…..Can I adjust the IAC to 5-10% in the tune? The throttle blades do looked close when you just take a look at them….I will check the MAP at Idle….here is what it looks like now

[RocktimusPryme]

IIRC you are supposed to do the mechanical setting of the IAC after you are at operating temp. By all means, check me on that, but I think thats what the manual said. So if you havent tried resetting your IAC, I would do that first per however the manual states to do it.

If the setting is from 2 to 10, and yours is at 2 or 3 maybe try it at 8 or 9 and see if that makes a difference.

[Dlaw455]

Originally Posted by yellow1098

I am running the exact same throttle body…..Can I adjust the IAC to 5-10% in the tune? The throttle blades do looked close when you just take a look at them….I will check the MAP at Idle….here is what it looks like now

Back those primary and secondary screws all the way out until they are not touching the throttle cams.. I would then start by getting it to idle by adjusting just the primary one 1/2 turn at a time just like a carb. Make sure to reset your throttle position sensor once you find the right position. Also make sure your timing is correct by setting it to static while running and checking the value matches the balancer. The IAC at idle will vary and together with tining adjust automatically to find your target idle rpm. What is your target idle speed anyhow?

[Dlaw455]

Originally Posted by RocktimusPryme

IIRC you are supposed to do the mechanical setting of the IAC after you are at operating temp. By all means, check me on that, but I think thats what the manual said. So if you havent tried resetting your IAC, I would do that first per however the manual states to do it.

If the setting is from 2 to 10, and yours is at 2 or 3 maybe try it at 8 or 9 and see if that makes a difference.

Yes set IAC when engine is warmed up. Otherwise there's a whole bunch of enrichments going on and IAC will probably be high depending on the idle speed vs engine temp curve. You cannot reset IAC but do reset throttle position sensor whenever the idle screw gets adjusted when dialing IAC to be around 8% at warm idle.

[yellow1098]

I have my target idle set right now at 950….I would ideally like it around 1,000 but I was trying to set it low to adjust for this situation especially in park

[Dlaw455]

Gotcha. Back those idle screws out and then see if it idles down. Probably will need pedal to keep running at that point. If you're using the built in MAP sensor, make sure you have that hose hooked up at both ends too.

[RocktimusPryme]

Originally Posted by Dlaw455

Yes set IAC when engine is warmed up. Otherwise there's a whole bunch of enrichments going on and IAC will probably be high depending on the idle speed vs engine temp curve. You cannot reset IAC but do reset throttle position sensor whenever the idle screw gets adjusted when dialing IAC to be around 8% at warm idle.

Reset was maybe the wrong word to use. I just meant go through this, copied from the manual.

If the “IAC Position” value is showing zero, you must close the throttle plates until it reads a value of 2-10. Slowly turn the throttle shaft
adjustment screw on the throttle body out (counter-clockwise). If the IAC position is “stuck” at 0, it is likely that the engine is idling at a
higher speed than you have set the target idle speed for. You need to adjust the throttle plates to resolve this issue.

If the “IAC Position” value is greater than 10, it is a good idea to open (turn the throttle shaft adjustment screw in, clockwise) the throttle
plates until the “IAC Position” value is between 2 and 10. Note that if you open the throttle plates such that the “TPS” position goes above
a value of 0, you will need to shut the vehicle off and perform a TPS AUTOSET. Then restart the vehicle and continue adjusting the throttle
plates. Once the TPS goes above a value of 0, the ECU goes out of its “idle” mode and will lock the IAC Position to a fixed value.

[Dlaw455]

Yup agreed. He needs to get those idle screws on both pri and sec backed all the way out and then set the primary to get it to idle around 8% iac and make sure to reset throttle position with key on.

[R 70 Judge]

I agree with the mechanical adjustment of the throttle body to start. Don’t forget to do the tps auto set after any adjustments. Have you taken any datalogs? I’d be curious to see what the timing is doing when the idle starts rising

[yellow1098]

Thanks boys …Ill try and reset the setup and start fresh with this process….I feel like I initially set it up this way….but I had a friend help me that’s no longer around… I will try these steps and see if it fixes the issue

[yellow1098]

Originally Posted by R 70 Judge

I agree with the mechanical adjustment of the throttle body to start. Don’t forget to do the tps auto set after any adjustments. Have you taken any datalogs? I’d be curious to see what the timing is doing when the idle starts rising

I can data log it when i drive it tomorrow….the only current data logs I have now are passes at the track which wouldn’t apply to the issue at all

[krisr]

There's also 2 settings to look at if you have a hanging idle that won't return to target. Under Idle --> RPM above idle to start ramp and Idle --> RPM above idle to re-enable idle control. Experiment with those once you get your IAC %age back to about 1 0% when hot and make sure your Idle Spark control is enabled. The last 5.3 turbo LS car I did, I used 70 for P and 90 for D. Car idles great. Returns every time back to target.

[R 70 Judge]

Any progress on the hanging idle?