Dies at start up, mild surge

Dontknowchit · May 15, 2025

I have been reading through the surging Idle checklist. Last night I did a smoke test and was able to attack a very minor vac leak. same symptoms today, thinking it is the IAB/IAC but i know that is a easy blame. symptoms are:
-Cold start, engine dies but not right away, sometimes twice. (checklist says this is big indicator)
-Minor surge. Does not get out of control like I have had before but slowly bounces 50-100 RPM, enough to hear but exteremly mild.
-Pulled IAC plug while running warmed up and nothing happened, no real change
-Idle is set kinda high~750 as that is where it seems to want to be the smoothest. (it's got a vortech, TB, and manifold upgrade)
-Idle seems to get a bit better after fully warm but minor surge never truly goes totally away.

-Planning on puling and cleaning after work but this is a recent replacement. Reasonable to clean it and then shoot a little WD40 in there?
-Going to try the Dx that is in the surging idle checklist but not sure if I understand it correctly.
-I believe my TFI is rather old, while that is not on the checklist, could this be Symptom of a bad TFI? Have been hesitant to replace preventitivley as I know its hit and miss even with motorcraft branded replacements.

Dontknowchit · May 15, 2025

Well, it's not the IAC and it's not the TFI.....

Dontknowchit · May 19, 2025

-Well saw something else that suggested it was the salt 'n peppa shakers being dirty. Hosed them out with electrical parts cleaner, new dielectric grease.
-Checked the recently cleaned MAF, it was still clean, hosed it off anyway.
-Pulled the IAC on startup, had to give it gas to turn over and surge was way worse and it died (blade adjusted to ~750rpm) so the IAC is not causing the surge, but rather chasing it. Plugged it back in and restarted it.
-Knowing I would have to do yet another TPS adjustment, turned the blade screw to increase idle a bit and this really seemed to calm the surge a lot.

Had it idleing at prob 850-900 and it was much more steady (iac in). Could not tell if it was just finally getting heat in it and switched to open loop or if it just wanted to be higher idle to not struggle. Put a fan on it and walked away. The coolant temp sensor is new.

I'm running out of ideas, sensors, and troubleshooting. Is it reasonable that due to the supercharger and the bigger injectors that it just wants to idle way higher?

Drove it to church yesterday and parked it on a incline, after services and meetings~3 hours I went to restart and did not want to start wihtout a fair bit of throttle input. Just for sanity, going to check fuel pressure (have to borrow gague from friend) but running 255 pump, new filter, and new FPR (non adjustable).

Dontknowchit · May 19, 2025

I stumbled upon this video, instructs that you pull the spout before base idle reset, I did it......it really seems like it worked. went through 3 strart cycles and the idle is not surging and it setteled in at a lower RPM. I think its too soon to tell. need a few more true cold starts, but I've never seen that you pull the spout to do base idle reset.....

View: https://youtu.be/s5W_n77YKZM?si=Vni8J5Ytl7dA5olf

Noobz347 · May 19, 2025

Admittedly, I don't see the actual procedures posted up much but here is the one that I've become accustom to:

It's the second post of the Surging Idle Checklist:

Post in thread 'Help me create the "Surging Idle Checklist"'

Apr 10, 2005

OK, now you have gone through the list and eliminated most of the possible problems. Now your mechanical and electronic problems are fixed, you can set the base idle speed.

Setting the base idle speed:
First of all, the idle needs to be adjusted to where the speed is at or below 600 RPM with the IAC disconnected. If you have a wild cam, you may have to raise this figure 100-150 RPM or so. Then the electrical signal through the IAC can vary the airflow through it under computer control. Remember that the IAC can only add air to increase the base idle speed set by the mechanical...

89ripper · May 19, 2025

Ive never heard about pulling spout neither but i have to ask, what is your timing set at? Also i mustve missed but are you running a radical cam in this?
When i had surging problems I did the 10 pin connector fix, (salt/pepper shakers) and it solved all my problems

Dontknowchit · May 20, 2025

Noobz347 said:
Admittedly, I don't see the actual procedures posted up much but here is the one that I've become accustom to:

It's the second post of the Surging Idle Checklist:

Post in thread 'Help me create the "Surging Idle Checklist"'

Apr 10, 2005

OK, now you have gone through the list and eliminated most of the possible problems. Now your mechanical and electronic problems are fixed, you can set the base idle speed.

Setting the base idle speed:
First of all, the idle needs to be adjusted to where the speed is at or below 600 RPM with the IAC disconnected. If you have a wild cam, you may have to raise this figure 100-150 RPM or so. Then the electrical signal through the IAC can vary the airflow through it under computer control. Remember that the IAC can only add air to increase the base idle speed set by the mechanical...

jrichker

I've read this thing probably 50 times over the years and 3 foxbodies and I've never caught that part! Always used this as the guide for surging idle but not base reset.

Dontknowchit · May 20, 2025

89ripper said:
Ive never heard about pulling spout neither but i have to ask, what is your timing set at? Also i mustve missed but are you running a radical cam in this?
When i had surging problems I did the 10 pin connector fix, (salt/pepper shakers) and it solved all my problems

I don't think I have a cam but I could as motor was rebuilt before my ownership. I do though have a vortech which may be lowering vacuum at high idle by pushing more air through a cracked throttle blade than expecting.

AeroCoupe · May 20, 2025

Is the car tuned?

Dontknowchit · May 20, 2025

No, I have not yet. Nobody local wants to touch it and I have not yet saved enough for the stand alone ECU. Hard enough to find anyone that wants to mess with these cars at all, much less anything without a Holley ECU. The 3 semi local and 2 multi hour drive shops I checked all only do Holley/HP tuners or modern ECU. Hopeful to talk to more folks at Ford takeover this fall to see if I can find any shop.

AeroCoupe · May 20, 2025

Where do you live?

Dontknowchit · May 20, 2025

AeroCoupe said:
Where do you live?

Nashville area

AeroCoupe · May 20, 2025

@95steedamustang - you know any SCT custom tuners in the Nashville area?

95steedamustang · May 20, 2025

^^^^^
Only in the East TN area but thats 3 hrs away.

Dontknowchit · May 20, 2025

95steedamustang said:
^^^^^
Only in the East TN area but thats 3 hrs away.

Will they touch a fox? It would obviously have to be "a trip" but do they still mess with stock computer cars?

95steedamustang · May 20, 2025

Dontknowchit said:
Will they touch a fox? It would obviously have to be "a trip" but do they still mess with stock computer cars?

Yep. Fox and anything 79-04

Noobz347 · May 20, 2025

ROOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOAD TRIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIP

Dontknowchit · May 20, 2025

95steedamustang said:
Yep. Fox and anything 79-04

Need names and numbers!

Willybill32 · Jun 7, 2025

Dontknowchit said:
-Well saw something else that suggested it was the salt 'n peppa shakers being dirty. Hosed them out with electrical parts cleaner, new dielectric grease.
-Checked the recently cleaned MAF, it was still clean, hosed it off anyway.
-Pulled the IAC on startup, had to give it gas to turn over and surge was way worse and it died (blade adjusted to ~750rpm) so the IAC is not causing the surge, but rather chasing it. Plugged it back in and restarted it.
-Knowing I would have to do yet another TPS adjustment, turned the blade screw to increase idle a bit and this really seemed to calm the surge a lot.

Had it idleing at prob 850-900 and it was much more steady (iac in). Could not tell if it was just finally getting heat in it and switched to open loop or if it just wanted to be higher idle to not struggle. Put a fan on it and walked away. The coolant temp sensor is new.

I'm running out of ideas, sensors, and troubleshooting. Is it reasonable that due to the supercharger and the bigger injectors that it just wants to idle way higher?

Drove it to church yesterday and parked it on an incline, after services and meetings~3 hours I went to restart and did not want to start wihtout a fair bit of throttle input. Just for sanity, going to check fuel pressure (have to borrow gague from friend) but running 255 pump, new filter, and new FPR (non adjustable).

Have you considered having the stock ECU checked? ECUExchange is quite reasonable and they found stuff on my stock ECU.

Dontknowchit · Jun 8, 2025

I had but then realized I have a a9p, not a a9l, but I have a manual. At this point, I'm looking at stand alone ecu options. Does not feel like 200 towards fixing a computer that is already not right for my car is money well spent.

Dies at start up, mild surge

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Stangnet Facilities Maint Tech... Er... Janitor

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lube between the nut and the face. I know my lubes

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lube between the nut and the face. I know my lubes

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lube between the nut and the face. I know my lubes

I tend to be on the ocd side…

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I tend to be on the ocd side…

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But at least it's tight!

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