Infamous Idle Hanging Issue....need help.

[BOOM_FIST]

Alright....before you start flaming with me starting another thread, I have used the search option and came up with nothing similar to my issue.


OK......so, I've read all about these idle issues with our Stangs and eventually came across the IAC restrictor plate "mod". I first cleaned my IAC and MAF with MAF cleaner and Q-tips. All is spotless. Then, I bought one of these restrictor plates off of ebay for like $3.50 and installed it yesterday afternoon. I used the smallest hole (don't know exactly what it measures) and all was good....until I took it for a test drive. Now, when I'm up in the RPM's and shift through gears, it does what it's supposed to, which is make the RPM's drop quicker and I love that. It does exactly that with no problems. It's when I coast in neutral or come to a stop, that the RPM's still hang high for about 3-5 secs at like 1500-1600 RPMs! And even when it drops back down after the 3-5 secs, my idle RPM's sit at like 900-1000RPMs instead of the normal 750-800?? I love everything about this restrictor plate as far as dropping the RPMs faster during driving....but the hanging idle really really annoys me to no end. In addition, I have a SCT SF3 tuner and thought that I would just lower the neutral idle and it'll be fixed. Nope. I have the driving idle set at the lowest it will go (can't remember at the moment) and the neutral idle RPM's set at the lowest it will go (456 RPMs IIRC), and it stills idles at around 900-1000 RPMs. What's the deal??? Do I need to adjust something else in the tuner?? Any SCT SF3 experts out there to help?? I will get all of my current settings from the SCT at lunchtime and list them to see what I need to change.

My mods are:

262 Comp Cams
Densecharger intake - K&N Filter
MSD ignition/coilpacks/wires
Stock TB/Plenum
Stock MAF
Stock injectors
Stock everything else motor wise.


Any ideas!?

 

[94-427]

A good cleaning with AC delco X-66A cleaner bought at any AC delco parts outlet
remove air inlet hose start engine and spray in throttle body [small hole feeding ISC] and clean every thing, engine running

 

[BOOM_FIST]

A good cleaning with AC delco X-66A cleaner bought at any AC delco parts outlet
remove air inlet hose start engine and spray in throttle body [small hole feeding ISC] and clean every thing, engine running

I have cleaned everything, fairly well. I have taken the TB off and completely cleaned it with TB cleaner and Q-tips. Taken off the IAC valve and cleaned with MAF cleaner with Q-tips. Sprayed the MAF sensor with MAF cleaner. Checked all hoses and clamps, no leaks that I can see/hear.

I can be cruising at 40 MPH in 5th gear with the RPMs around 1200-1300, I push the clutch in while still coasting, and the RPMs jump up to 1700, and hang there until I come to a complete stop. Then 3-4 secs later, it comes back down to 900-1000 RPMs to idle when completely stopped. That's still not the correct neutral idle speed even though I have it set to the lowest on the SCT. It sounds like ass and it's annoying as hell. I'm already thinking about removing the plate if I can't figure this out soon. All was "normal" before the plate.

 

[98mustanggtkid]

I say try removing the plate, if its fine you know exactly what it is and you could try a bigger hole. if not then you know its something else thats where I would start

 

[BOOM_FIST]

I say try removing the plate, if its fine you know exactly what it is and you could try a bigger hole. if not then you know its something else thats where I would start

This is what I plan on doing once it stops raining it's ass off here in MD. Might try the bigger hole and if that one doesn't work, probably just remove it all together.

 

[98mustanggtkid]

I say try removing the plate, if its fine you know exactly what it is and you could try a bigger hole. if not then you know its something else thats where I would start

good plan, let me know how it goes
This is what I plan on doing once it stops raining it's a*s off here in MD. Might try the bigger hole and if that one doesn't work, probably just remove it all together.

 

[2002BLGT]

the car is supposed to keep the idle a little higher until you come to a stop its programmed that way from Ford , if its too high most likely cause is a vacuum leak

 

[BOOM_FIST]

So I flipped the plate around to the bigger hole, and it put the neutral idle back down where it's supposed to be, but now the slow falling RPMs when I shift and drive is back, the whole purpose of me getting the plate. So I guess you really can't have both unless you get your car professionally tuned. I plan on boring the smaller hole out a little bit to try and get an even medium of the two holes and see what that does. Worst case, I'll make some more plates and keep doing the trial and error thing.

More importantly, messing under the hood has made me find a few more minor issues....coolant leak!!! Woo-Hoooo!