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More Idle issues and a Question about tunes!

775 views 7 replies 4 participants last post by  Joshua99 
#1 ·
My Mustang has been idling very inconsistently now that the weather is getting colder. After the car warms up, the idle will be from 500ish to 800ish and bounce in between those throughout the entire drive.

When coasting in neutral it sometimes will hover at 800 or so consistently, but usually it will bounce in the 500-800ish range.

The driver side exhaust manifold has a very minor leak, at least it sounds like it to me.

Also Im running a Strategy 87 tune from SCT (the preloaded tune, not custom) and I have a bunch of bolt on mods. I feel as though I need to get a custom tune to really get the car to run better, but I'm not exactly sure about that.
Ive cleaned the TB, EGR, New IAC, adjusted TPS
Bolt ons: CAI, TB, Plenum, X-pipe, and Magnaflow catback

Really Im asking if fixing the exhaust manifold or changing to a custom tune should help me out. Or if its something completely different!
 
#2 ·
Have you verified there are no vaccuum leaks? This, to me, has vaccuum leak written all over it....

As far a custom tune, not really needed in your case BUT it will help pull all your mods together (by custom I mean a dyno tune).
 
#7 ·
Sometimes an exhaust leak will have the same symptoms as a vacuum leak. A couple things, the tps is not an adjustable item. You can change your voltage on the tps thru turning it but once the extra goes into sensor calibrate mode it will set closed throttle voltage where it wants it. Also, try loading the stock tune back in and see what it does. Sometimes when it comes to idles the tunes can be finicky. Normally you will have timing advance set a couple degrees advance over idle but it'll be a few rpm lower than what you want idle to be. Meaning when idle drops the timing advances making the engine speed up so it goes back to target rpm. Canned tunes don't really adjust that because every car runs different and they can't really tell what it wants without logging or being there.
 
#8 ·
Thanks for the response!

Back on the stock tune now and its runs a bit smoother overall, but the idle drop when I stop is more significant then before (probably because I raised the idle a bit on the tune). Im thinking I just need to fix the intake manifold and the exhaust manifold and all will be right in the world again
 
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