Car is tuned, runs great, at idle it dies when all the electronics are on

Makoto

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voltage at the alternator is a solid 14.6 on start and as it heats up drops to around 14V. battery stays topped off and the new fan acts like the old fan so that isn't the problem.

what rpm does it idle at?

1000

What year is the car? I know base idle reset procedure for mine asks to unplug battery 30 mins to clear the ecu memory. Unplug IAC and start car set the mechanical idle speed and shut off the car. Plug the IAC in with all electronics and AC off and start the car and let it idle for 2 mins and then shut it off again. Then start the car with all the electronics on and the AC which will kick on your high speed fan and let it idle for 2 mins. This allows the car to learn the idle characteristics with no load and full load.

its a 97. that makes sense so I might try it tomorrow. its never been reset and run with the low speed circuit working correctly. i got that working after the tune.
 

07GtS197

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Why does it idle so high? It sounds like maybe there’s a vacuum leak.
 

Makoto

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Why does it idle so high? It sounds like maybe there’s a vacuum leak.

i've sprayed starter fluid all over this thing and I don't see how it has a leak when it holds vacuum so well that i can pull the dipstick when its running and introduce a vacuum leak at will.

today i took the IACV back to autozone and got a new one. same issues. here's the pieces of the puzzle

1. with AC on when fan kicks on the car almost dies, lugs, then comes back to life.
2. pressing the brake pedal suddenly at idle will make the car die
3. car idles at 1K steadily which is kinda high already

here's something interesting. I did the base idle reset someone suggested (didn't work) but I noticed this new thing:

4. with IAC unplugged I can crack the throttle with my foot and hold it dead steady at like 700rpms and its all fine

I'm kinda wondering if the TB needs to be cracked with the screw a tiny bit more which is causing the IACV to work too hard and maybe it can't keep up when everything is lugging the motor. I know we're not supposed to do that but... I did it a long time ago and maybe when i put it back to where it was i went too far...
 
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ttocs

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the starter fluid does not always show leaks. You would be better off getting a cigar and doing a smoke test to find out. How old is your brake booster?
 

lwarrior1016

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He doesn’t have a brake booster, it’s hydro boost.

It sounds like it’s an airflow problem to me. I’d say try to crack the throttle blade open little by little and see if you can make it idle.
 

Makoto

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I got it to idle without the IACV plugged in so I think that might have been part of the problem since apparently setting base idle is supposed to be done by unplugging the IACV initially. I noticed when i crank it up initially I hear some sucking whistling noise near the IACV.

I'm going to check the upper plenum for vacuum leaks and maybe re-torque it in the proper sequence even if i don't find anything.

if starter fluid reveals nothing I'll get a thing of propane. I talked with the tuner today and he gave me some protips on adjusting the idle which seemed to help some so I might just try a base idle reset again tomorrow now that I have the throttle cracked a smidge (after I test for that possible leak of course).

This has to be something small. the tuner said my engine is strong as hell and everything did exactly what it should've done but we had a fan issue before he could tinker with the idle stuff.
 

Notthenow

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The brakes drag down the powersteering pump pulling down the rpms. Hydro does that.
 

07GtS197

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How is your pcv plumbed? The best way to look for a vacuum leak IMO is with a scan tool that can datalog.
 

ttocs

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The brakes drag down the powersteering pump pulling down the rpms. Hydro does that.
Hydroboost is not electrical right? So I am not sure how the problem with the fan relates since it is electrical. If it is creating enough of a load that the motor can't power it, something is up and it seems like something different from the fan unless the alt is creating a load the motor can't power and then something is really wrong. I almost wonder if the serpentine belt shouldn't be removed and check that all the pullies are spinning free.
 

Makoto

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Hydroboost is not electrical right? So I am not sure how the problem with the fan relates since it is electrical. If it is creating enough of a load that the motor can't power it, something is up and it seems like something different from the fan unless the alt is creating a load the motor can't power and then something is really wrong. I almost wonder if the serpentine belt shouldn't be removed and check that all the pullies are spinning free.

the common denominator is this: anything that loads down the engine at idle causes it to putter out.

electrical stuff puts load on the alternator which increases resistance there
PS related stuff (brakes, in this case) put load on the engine which increase resistance there

the engine is super healthy so that isn't at fault
IACV is good
fan is good
electrical system as a whole is good
PS pump seems to spin pretty freely (took the belt off and checked)

today im going to check the PCV's (they're new but who knows?)

here's the pcv routing. from what i can tell is what ford says to do

pcv routing.png
 

Makoto

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i just realized i had 1 pcv on each valve cover so that couldn't have been helping.
removed the passenger one and replaced it with a straight pass through
idled higher and seemed to help but still struggled with the brakes on and almost died when the fans kicked on.

gonna try base idle reset again after a while now that I have the pcv system hooked up right.
no sign of any vacuum leaks. soaked the hat with starter fluid, not a blip.
 

Makoto

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I wonder if the tune was affected by the pcv set up error...

so the idle, yes, but at full trot it should be fine.

I removed the passenger pcv, replaced it with a straight pipe, did base idle reset, and now the idle is higher (like 1250-1300rpms) but i think that's a good thing because the IACV was overworking itself. seems to be doing better. i'll check on her tomorrow. All i know to do is fix things until i run out of things to fix.

here's where it idles now. Based on this, I think the tune is now like "okay be open this much at idle" and so it rises to this. without the IACV its like 760-800rpms.
This is after driving her around for a bit so she's nice n hot. Seems like we might've gotten to the bottom of this.

hidle.jpg

i also met a nice police man today.

hipoliceman.jpg
 
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Notthenow

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Test driving can do that, he understood right?
Yeah, I figured idle would be most affected. Not like the carb days when you turned an idle screw to set it... The air flow the iac controls is messed up when any air, post sensor, entering the tb. Good catch, I hope you got it!
 

ttocs

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the tune has a set rpm that it tries to keep the motor at depending on temp. The IAC has a hold position that it stays at(programmable) when you are on the throttle but when you are off the tune reads the rpm and then will open the IAC if its below the point its programmed to be at or close the iac if its above it. The tune should not be holding the idle at 1200 or have changed the rpm it is supposed to be at with the physical changes you made if it is there is a big problem with it.
 

lwarrior1016

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I’d have to look at how a stock file controls idle compared to Holley, it is different. The gm stuff that I have tuned, you will set a base idle airflow telling the IAC to open a certain amount so you can get an idle. That is called open loop idle. Closed loop idle will make adjustments to the iac by itself to target an rpm. If this is set to open loop idle and the tuner command X amount of IAC to get the airflow required, then you introduce extra air, the iac will still add X amount on top of the extra air. So it’ll idle higher.
 

Makoto

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I’d have to look at how a stock file controls idle compared to Holley, it is different. The gm stuff that I have tuned, you will set a base idle airflow telling the IAC to open a certain amount so you can get an idle. That is called open loop idle. Closed loop idle will make adjustments to the iac by itself to target an rpm. If this is set to open loop idle and the tuner command X amount of IAC to get the airflow required, then you introduce extra air, the iac will still add X amount on top of the extra air. So it’ll idle higher.

yeah my tuner said he kinda had to peg the IAC because my throttle screw wasn't right and the pipe to the crankcase between the MAF and TB was essentially blocked off.

oh and the cop was cool. gotta get it sorted to get inspected to get it registered to get plates.
 
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