HIGH RPM WHILE SHIFTING

90sickfox said:

Still sounds like it to me. So you had to shim the solenoid body away from the housing to get the pintle to take the pressure off the disc...allowing the unit to seal ?

You are correct that air should not pass through both sides when off. Seems like a legit fix.

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Thanks that’s what I did and it has been working consistently.

7991LXnSHO said:

Are you close enough to go for a ride this spring? My TB and IAC whistle, and I have not done the fix so I can tell when the IAC is working.
If an IAC or EGR valve is leaking, idle will be a problem.

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That sounds like more than one leak, mine was not making a whistle sound, only hanging high rpm while shifting or coasting in neutral. I reached a point that even driving slowly in first or second it felt like the cruise control was engaged.
Now all of that is gone and very pleased

7991LXnSHO said:

I think you are still operating on the wrong theory of operation and fought a bad IAC and did not set the base idle speed like recommended in post #2 here.

Help me create the "Surging Idle Checklist"

Updated 26-Oct-2019 to clarify creeping idle RPM increase as the car is being driven. Many of you are familiar with the "Cranks OK, but No Start Checklist for Fuel Injected Mustangs" checklist and the No Crank Checklist. They are very effective in finding and eliminating the problems by use of...

www.stangnet.com

The IAB, aka IAC, can only add air to raise the idle speed. It is a normally closed valve. If yours needed shimmed to close, you spent a lot of time trying to band aid then fix it.

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I think you’re wrong in your assumption about me not setting the base idle correctly. I did set the idle the same way but used different values. The values in that checklist are for a stock engine, it specifically states to add more idle speed if using different components and that’s what I did. As far as the IAC being “fixed” or bandaid by way of gaskets in between the valve body and the solenoid, well I’m not so sure about that assumption either. If you can help me understanding this... What part of the valve is bad? The valve itself, or the solenoid? The valve is nice and clean, there is not even a trace of carbon and the disc moves freely, the solenoid is not shorted and it comes in and out when energized. I’ve seen those valves brand new out of the box and they have open flow. Are my gaskets in between of the two pieces a permanent “fix”? Based on my “wrong theory” I truly believe so, and I will prove it with six more valves I have in the same conditions (“Bad”) to my disposal as R&D. I predict all of them will work flawlessly with my “Bandaid”

Boostedpimp said:

Yeah I'm confused now.. so you had to add extra gasket to the iac valve to shim it further away from the manifold for better valve sealing?

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Nothing to do with the manifold, the gaskets go in between the IAC aluminum body and the solenoid. As pic shows in page 1

7991LXnSHO said:

If the air goes through a new valve that has power to it, it is bad. They are a normally closed valve. If you get several new ones that do not seal, they made a bad batch.
I seem to miss the part about a feeler gauge and certain amount of turns with this procedure. I do have the idle set a bit higher due to a larger cam.

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It is possible that I have all of those valves from a bad batch, but then again if I will be able to "fix" all of them by making a gasket material spacer in between the valve body and the solenoid it will be great. With regard to setting the idle speed with a 0.010" feeler gauge it is not that complicated even with a big cam. For this I'm using a spacer commonly used on some old ford Taurus in between the TB and the IAC which has two set screws. The advantage of using that spacer is that once you set the TB butterfly opening as your base idle you can add more air thru those set screws bypassing the IAC without disturbing the TB stop screw and or the TPS. That works really nice for me and like I said with that idle setting procedure plus the spacer plus the modified IAC the RPM's are no longer hanging high while shifting or while cruising in neutral. The aluminum spacer works great for really fine idle adjustments with the obvious and proper ECU resetting after every adjustment.

All I'm saying and not in a contentious way, it's been working flawlessly for me.