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Dont be mad that you didn’t specify. Why would it be unreasonable to test it in the condition where it actually has the issue?Aren’t base idle resets done with the engine warm?
Lol... Nobody is asking you to do an idle reset, nobody told you to warm it up before checking the iac. You're arguing with the only person actually trying to help you troubleshoot instead of just doing what is asked of you. Good luck.
 

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Discussion Starter · #42 ·
Lol... Nobody is asking you to do an idle reset, nobody told you to warm it up before checking the iac. You're arguing with the only person actually trying to help you troubleshoot instead of just doing what is asked of you. Good luck.
Im clearly using the idle reset as an example of doing adjustments and diagnostics with the engine warmed up. I thought that was pretty obvious and I further explained why I tried it with the engine already having some heat in it.

And once again, no one told me to check it cold either. They did not specify. If you’re going to berate me for “not following instructions” then perhaps you should provide clearer instructions.

The “only person actually trying to help me” hasn’t offered a shred of any explanation whatsoever aside from “the engine isn’t getting enough air”. All they’ve done is repeat what I already posted, and hurl insults my way. I really don’t understand why you guys just can’t talk about this like adults, and I don’t understand why you’re coming here to defend them when you have nothing further to add to the discussion.

If anyone wants to offer advice and have a civilized conversation about this like adults, I’m game. I’m not interested in bickering back and forth and I’m not interested in dealing with internet tough guy edgelords.

Thanks.
 

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I plan on starting it up when cold and unplugging the IAC to see if the car dies. If it keeps running and potentially doesn’t stall (despite probably exhibiting some surging) I’ll know it’s the IAC
To indy's defense, you did say you'd start it cold and unplug IAC.

Also, he comes off as a complete dick sometimes (OK, most of the time), but if you follow his directions and think of what and why he's suggesting certain test or asks certain questions, you'll get through it.
 

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Discussion Starter · #44 · (Edited)
To indy's defense, you did say you'd start it cold and unplug IAC.

Also, he comes off as a complete dick sometimes (OK, most of the time), but if you follow his directions and think of what and why he's suggesting certain test or asks certain questions, you'll get through it.
To indy's defense, you did say you'd start it cold and unplug IAC.

Also, he comes off as a complete dick sometimes (OK, most of the time), but if you follow his directions and think of what and why he's suggesting certain test or asks certain questions, you'll get through it.
That’s fine, I just meant that I would start it cold and wait until it died, which as I understand it meant the car had heat in it. I should have clarified.

I’m going to try it cold later this evening
 

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honestly? i am gonna ask you to unplug the IAC when the engine doesn’t run??????????
 

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Discussion Starter · #48 ·
So I went out just now and started the car up, and immediately disconnected the IAC. The idle dropped to about 500 RPM. The car barely stayed alive but did continue to idle for a bit. I did happen to notice that the fuel pressure, which was at 33-35 PSI before, was now hovering closer to 37 PSI. Not sure if that’s related or not.



My best guess as to what’s happening is that the idle is set too low via the set screw, and the IAC is held or stuck wide open. This allows it to idle just fine while in open loop, but as soon as it goes into closed loop, the IAC has no further to open and the car shuts off.



My other theory is that the IAC is just clogged or stuck in a partially closed position where it can’t open any further, with the same result. This would make more sense since the problem appeared after the car had been driving fine for a while. The IAC could have deteriorated or have had time to get gummed up.



So maybe if I adjust the idle via the set screw with the IAC disconnected, or if I perform a base idle reset and replace the IAC with a fresh one, that might solve it. But I’m really not sure.



Any thoughts?
 

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'87 Cougah 428W - ⚡Cougar7.0⚡
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Seems the IAC is working. What else could have changed to provide less air? Do you have a PCV on the car?
 

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Discussion Starter · #50 ·
Seems the IAC is working. What else could have changed to provide less air? Do you have a PCV on the car?
Not sure. I haven’t changed anything on the car. I do have a PCV line that goes back into the throttle body. I checked the line, it’s newer hardware and isn’t cracking or anything. The clamps are still secure
 

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Do you have the hose from the valve cover to the throttle body connected?
 

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Also check that the PCV isn't clogged or otherwise not pulling air - it's in back of the intake.
 

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Does it have a tune? If so do you know who it is tuned by? If the ecu thinks it's getting hot and has a decipha tune (even his free base tune has it) it may be shutting off due to over heat protection. Overheat protection allows the car to run for about 15 seconds before dying again.
 

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Discussion Starter · #56 ·
Does it have a tune? If so do you know who it is tuned by? If the ecu thinks it's getting hot and has a decipha tune it may be shutting off due to over heat protection. Overheat protection allows the car to run for about 15 seconds before dying again.
I do not believe it has a tune, and no aftermarket chip or anything. That would make sense, but how would this develop suddenly and how would I fix it? Would the ECT be involved in sending a bad signal that the car is too hot?
 

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PCV meaning the line that runs from the valve cover to the throttle body?
No, that's the return air line. The PCV is inserted into a grommet in the back of your intake and has a hose that goes to vacuum tee under the intake overhang - assuming stock configuration.
 

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I do not believe it has a tune, and no aftermarket chip or anything. That would make sense, but how would this develop suddenly and how would I fix it? Would the ECT be involved in sending a bad signal that the car is too hot?
yes, IF the ect is sending an incorrect signal, the ecu could think its running hotter than it really is. The stock tune doesnt have overheat protection so this would only happen if your car has a chip based on A9L2 which is deciphas base tune. There are a lot of DIY tuners and probably some other shops using it as their starting point. You can tell if it has a chip by pulling the passenger side kick panel and pulling the ecu down. I would think if it has a HCI upgrade it would have a chip but maybe it doesnt. The gauge and the ecu use different sending units so the gauge could read normally but the ecu could think its over heating. I would at least verify if it has a chip.
 

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Discussion Starter · #59 ·
No, that's the return air line. The PCV is inserted into a grommet in the back of your intake and has a hose that goes to vacuum tee under the intake overhang - assuming stock configuration.
I just checked it, it looks good as far as I can tell. All that plumbing is apparently new from when the new intake was installed
 

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Discussion Starter · #60 ·
yes, IF the ect is sending an incorrect signal, the ecu could think its running hotter than it really is. The stock tune doesnt have overheat protection so this would only happen if your car has a chip based on A9L2 which is deciphas base tune. There are a lot of DIY tuners and probably some other shops using it as their starting point. You can tell if it has a chip by pulling the passenger side kick panel and pulling the ecu down. I would think if it has a HCI upgrade it would have a chip but maybe it doesnt. The gauge and the ecu use different sending units so the gauge could read normally but the ecu could think its over heating. I would at least verify if it has a chip.
I just looked, stock computer no chip unless I’m missing something
 
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