Need help, I've ran out of ideas..

[mustang4lyfe]

Ok guys bear with me here I have alot to say and I would appreciate some help. Recently my car has been dipping into the low rpms after I rev the motor and then spiking back up to normal idle. I first tried to just clean my IACV but that didn't do the trick, so I purchased a new one, which was not a motorcraft one it was a BWD brand from orileys. Along with this I also bought the accufab 70mm TB and plenum combo off AM. I installed them all today, and I put in the normal IACV gasket, not the restrictive one to make the hanging rpms go away, because i tried to use that gasket but the car would idle at 1300 rpms where before with the stock plenum and TB it idled fine. I have an o/r prochamber midpipe and borla stinger catback on the car, along with a cold air intake and steeda underdrive pullies. I also have the car tuned with my Bama handheld tuner. After having everything installed and the car running, I noticed that even with the new IACV the rpms still dip after revving. Also now a new sound has showed up, when I'm slowing down and push the clutch in when the rpms hang I can hear almost like a humming/howl/vibration sound coming from upfront where the instake is. And when I rev the car to 2k rpms it makes the noise and right before the rpms start to decent I hear almost like a Sneezing or quiet blowoff sound before the rpms drop. I made a videa here for everyone to see and help try and fix my trouble. Help is really appreciated I'm gettin a big headache over all of this. Please help and give me some things to try.

Also the rattling sound in the video is my U Joints I believe.

Link to Video ---> ‪YamahaEnergy's Channel‬‏ - YouTube

 

[04torktech]

My first though when I started reading this was your IAC valve but it seems you have fixed that. Now assuming all the vacuum lines are secured and there are no stragglers you could check a few other things. One would be the PCV valve. I believe if you PCV goes it will idle higher but you should check anyways. Remember the PCV is a one way valve so after you "unscrew" it and pop it out try to blow into it and you should be able to push air through one way and not the other with your mouth. The other thing it may be (and this doesn't make sense with the noise you are hearing) is your MAF. Before I put my supercharger on I ran a 90mm lightning MAF for a week cause I was doing a swap with a friend and he needed my stock MAF. During that time my car did very similar things the idle would drop until it would almost stall. I am assuming you have the stock MAF but it might be worth it to check and make sure it is clean and working properly because that can definitely affect your idle. Let me know how it goes. Good luck

 

[mustang4lyfe]

Thanks, I will try the PCV valve thing you suggested and also yes my MAF is stock, is there a certain way to clean it that I should follow by? and what do you think the howl kinda sound is that I'm hearing? is it just a noise that comes along with more airflow from the TB and plenum?

 

[mustang4lyfe]

Well i solved one problem which was the humming, it was the faulty IACV I just bought from orileys. Well taking that back and getting myself an actual IACV udner the motorcraft brand, paying the extra bucks for a better quality part. Hopefully that will fix the idle going low, since the one i just bought wouldn't because it was faulty in the first place..

 

[hotstang_46]

I would eliminate the following two. I believe it could certainly be a tune. Can you try putting it back to stock to see what happens? Have you checked the plugs?

 

[mustang4lyfe]

At first I thought actually getting the car tuned would fix it but it didnt, Thats some of the reason why I got a tuner so I dont think thats the reason, and I have not checked the plugs, tomorrow I'm going to order a new functional IACV the one I bought was faulty so I'll find out