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Something changed. I suppose you can do your re-set of the idle procedure and see it if sticks. It may help to diagnose the issue, it will also satisfy our curiosity.
 

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I just looked, stock computer no chip unless I’m missing something
They are pretty obvious when the computer is pulled out of the bracket. The chip plugs into the J3 port and you can clearly see it. You cant see it unless the computer is pulled down out of the bracket. It will be on the opposite side of the ECU as the connector and stick out of the case slightly. Might have duct tape over it to ensure it doesnt vibrate loose.
 

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Discussion Starter · #63 ·
They are pretty obvious when the computer is pulled out of the bracket. The chip plugs into the J3 port and you can clearly see it. You cant see it unless the computer is pulled down out of the bracket. It will be on the opposite side of the ECU as the connector and stick out of the case slightly. Might have duct tape over it to ensure it doesnt vibrate loose.
Yea I pulled the computer down and I didn’t see anything. The guy who sold me the car included two chips with it, not installed, that are sitting in my parts drawer so I was looking for something that looked like that. He said he didn’t have a chip installed but I wanted to be sure
 

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Discussion Starter · #64 ·
Something changed. I suppose you can do your re-set of the idle procedure and see it if sticks. It may help to diagnose the issue, it will also satisfy our curiosity.
I did try disconnecting the battery and letting it drain down and I also verified that the timing is set properly (14 degrees base timing) but I don’t know if it would make a difference as far as the battery disconnect.

I really would like to diagnose the issue but it seems as though I’m at a dead end. I also had my mechanic friend do a once-over and make sure everything looks good visually, and he couldn’t find anything. He’s been a Ford tech for 30 years and he’s done quite a few foxbody builds over the years so I dunno. He didn’t do any in-depth stuff though.

I may just have it towed to a shop honestly
 

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I was thinking you could crank the throttle stop screw a set amount (so you can undo it if doesn't do what you like) to get it to idle without IAC, then plug IAC in (obviously cycle key to re-learn TPS zero position.)
 

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Discussion Starter · #66 ·
I was thinking you could crank the throttle stop screw a set amount (so you can undo it if doesn't do what you like) to get it to idle without IAC, then plug IAC in (obviously cycle key to re-learn TPS zero position.)
This is a very dumb question, but which is the throttle stop screw and which way do I turn it? I just don’t want to start haphazardly turning screws
 

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there is NO dead end, unless you want to give up and take it to a diagnostic based shop?

Your IAC works, the wiring is good, and the ecm has control

There is NO base idle reset with a HCI change, base idle reset is for stock engine airflow

After a HCI, depending on cam, will open the throttle stop, so that idle is no longer controlled by the ecm, like a carb

people that do this dont know how the ecm controls idle speed or dont want to do it correctly, recalibration is the only way

are you running the stock throttle body?

the ecm has adaptive learning, this goes for fuel, and idle speed control, the more starts, the more driving, adaptive will start adapting to achieve target conditions in the calibration

since you cannot meet the calibration conditions, things get worse

so now that we have proven the IAC works,

its time to start at the beginning, check for codes.
 

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Oh, I thought you were familiar with this since you mentioned it earlier. You can do the below as an experiment, but it might make things worse, thus you would want to note how much you turn the screw so you can undo the change.

Throttle stop is here:
1074959


You're supposed to turn the throttle stop (clockwise in your case to increase the base idle) to where it's a certain number of RPMs below where it's set by the ECU (I can't recall and there's only misinformation published on the internet - I can't find a single legitimate site now! The internet blows as everybody has copy/pasted BAD info!). Anyway, after you do so you can turn the engine off, reconnect the IAC and see what happens when you restart it.
 

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closed throttle airflow, must equal what is inputted in the ecm for the stock throttle body

0.55lb/min
 

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Discussion Starter · #70 ·
Your IAC works, the wiring is good, and the ecm has control

There is NO base idle reset with a HCI change, base idle reset is for stock engine airflow

After a HCI, depending on cam, will open the throttle stop, so that idle is no longer controlled by the ecm, like a carb

people that do this dont know how the ecm controls idle speed or dont want to do it correctly, recalibration is the only way

are you running the stock throttle body?

the ecm has adaptive learning, this goes for fuel, and idle speed control, the more starts, the more driving, adaptive will start adapting to achieve target conditions in the calibration

since you cannot meet the calibration conditions, things get worse

so now that we have proven the IAC works,

its time to start at the beginning, check for codes.
I appreciate the explanation.

It has a “new” (installed by the previous owner) 65mm BBK throttle body. I’m actually going through the list of stuff now and he also put a new IAC, TPS, and IAT with all the associated hardware.

I unfortunately do not have a code reader and I don’t have any knowledge of how to perform the other ways to check codes (I’ve heard it can be done with a test light and some weird procedure) so I’m stuck for the moment.

Is there a type of code reader you could recommend that I should have? I’m just going to order one

thanks again
 

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contrary to most will say, unless you can match the airflow of the stock TB and keep long term IAC trims within spec

a throttle body increase in size, needs a tune/recalibration

for the code reader

amazon

or search youtube for the paperclip trick
 

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Discussion Starter · #73 ·

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Maybe I missed it, after you pulled the IAC when cold and it was still idling around 500rpm, did you let it run until it shut off (keeping IAC disconnected)?

When cold, as stated earlier, the engine needs more air (and fuel) than at operating temp. If it's idling cold with IAC disconnected, it should continue to idle when warm, so it wouldn't be an air issue.
 

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Discussion Starter · #77 ·
Maybe I missed it, after you pulled the IAC when cold and it was still idling around 500rpm, did you let it run until it shut off (keeping IAC disconnected)?

When cold, as stated earlier, the engine needs more air (and fuel) than at operating temp. If it's idling cold with IAC disconnected, it should continue to idle when warm, so it wouldn't be an air issue.
Yes, I let it run. It ran for a little bit, maybe 20 seconds or so, before dying. It didn’t just “shut off”, rather, it sputtered lower and eventually couldn’t hold idle.
 

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Maybe I missed it, after you pulled the IAC when cold and it was still idling around 500rpm, did you let it run until it shut off (keeping IAC disconnected)?

When cold, as stated earlier, the engine needs more air (and fuel) than at operating temp. If it's idling cold with IAC disconnected, it should continue to idle when warm, so it wouldn't be an air issue.


read first post
 

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Discussion Starter · #80 ·
How much compression? Broken valve spring can do something similar.
I have not done a compression test, but the heads and the entire valve train are pretty new with less than 5k miles on them (all Ford Racing and Trick Flow hardware for the valve train, including the lifters) and about 1k miles ago I had a professional go through and adjust the rocker arms and in the process I also had him replace all the pushrods and some other hardware (including guide plates) out of an abundance of caution. Also the car isn’t exhibiting other symptoms of compression issues at any RPM. The only issue it has is it dies at idle. It runs fine otherwise as far as I can tell
 
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