HKSevo

Hey guys,

I have a 1996 Mustang GT. Got it about a year ago now.
After i bought the car, the idle was pretty good. I would say it wasnt rough at all. As time went by, my idle has been getting worse and worse. I mean it still isnt horrible, it just is rough. The weird thing is, there is no variation in my rpms as far as i can tell by my tach. So its more like my engine is just not running 100% or something.

Ive put a little over 10k miles on it since January or this year. Ive done two oil changes since ive gotten it, with fully synthetic Royal Purple oil and Royal Purple oil change. Also, right before the first oil change that i did, like immediately before, i ran Sea Foam through a vacuum line hoping to fix the idle problem. After the royal purple and first oil change, I changed my plugs to some platinum spark plugs.

I have also cleaned out my IAC Valve with electronic cleaner a little before my first oil change.
And i run nothing but Cheveron 91 octane in this car, even though i know it doesnt really matter for a non-tuned stang and whatnot.

One last thing is m car runs at a higher rpm when warming up, higher than it was when i first got the car.

What is your guys input on this?

Is this an easy fix?
Im thinking maybe timing? Or spark plug wires? I dont know tho, knew to these 4.6L's...was more of an import guy before this mustang...still am a little shhhhh

Thanks for any help that you guys can give me I appreciate it!!!

MU71L4710N

you cannot clean the IAC valve per ford. cleaning it is SOMETIMES a temporary fix for SOME people, but does not guarantee any results and cleaning it will not fix a faulty IAC.

idle problems are almost always caused by the IAC. do you have any misfires while driving? misfires can be hard to tell at idle but should be really apparent when your WOT. you could try adjusting your throttle stop a little bit, your car might just be choking at idle (which usually means the IAC isnt fully doing its job).

and stop wasting your money on premium gas, you just said yourself you know it does nothing. it does not help your car to run cleaner, it gives you no horsepower, it doesnt have any positive results for your car what so ever. your just wasting money. but if it puts a smile on your face to know that your spending money you don't have to, then by all means keep doing it.

HKSevo

Okay well i think ill go mid-grade now until more upgrades haha

As for the IAC valve, do you suggest just buying a new valve?
Im a little hesitant to buy a $80-$120 dollar part if it isnt too bad right now and I dont know for sure if it this part ya know? Unless you guys can tell me for sure it is it, then ill purchase it.

Thanks for your info MU71L4710N! :]

MU71L4710N

well....

1) are you getting any misfires when your driving it hard?

2) i would try adjusting your throttle stop a little bit and see if that clears it up any. go to paladinmicro.com its cliffyk's website theres instructions for how to adjust your throttle stop. its a little hex screw on your throttle body that pushes the butterfly open a little bit.

HKSevo

Oh sorry i didnt answer your question. Ummm for misfiring, nope it doesnt misfire at all when driving hard.

Hmmm ill look into adjusting my throttle stop. Thanks for the info!

deviousgt

I was also having problems with my idle you can get a new IAC at autozone for $50 It probably needs to be changed I would try that see how it goes

HKSevo

Wow it is only $50 at AutoZone!!

O'Reilly cheapest one is like $89 bucks iirc on their website.

Thanks for the heads up!!!
Ill most likely go buy one soon so i can check that off the list if Im still having issues!

Gordon A

Change the IAC - You cannot fix them by cleaning them

I have gone through 2 IAC's on my 97 Mustang in the 6 years I have owned it.

Also, stick with regular gas, not mid or premium. Unless you have upped the compression your 4.6 is relatively low (8.5:1) and it runs fine on regular as it was designed to do. Any higher than this and you are just blowing $$$'s out of your tailpipes.