kanine

Any help would be appreciated, starting about 2 weeks ago my Stang has began to start sporadically idling a little rough. At idle, RPMS would drop to about 500 and car feels like it is going to stall and it bounces back up, the same happens when I put the car in neutral and coming to a complete stop, feels like there is a little vibration even at normal idle.

Driving and acceleration, everything seems fine. No engine light. Just under 32k and engine is stock. Car is DD and has about 4k since last oil change. So far, I cleaned the MAF and throttle body and it seemed to "fix" the idle for 2 days, and it's back to doing the same. Tried to capture it on video the best I can, but wasn't idling as rough today. First vid it happens in the beginning and second vid around 8 sec mark.



Third vid, RPMs does some wierd jumping up and down a bit.

I went to check all the hoses and everything and I noticed the crankcase tube? has a crack in it. Looks like it happened from rubbing on the engine cover, looks like just the top part of the hose and not cracked all the way through to cause a leak. It also feels like there's a hard plastic tube under that hose, so I don't think it's leaking. Oil, plugs, any suggestions? Thanks

DeeJayTJ

is yours by any chance having a voltage drop also?

my 13 is doing the same thing you've explained, but i have watched the voltage and have found that the voltage will drop to about 10 or 11 or so and then bounce right back up and idle just fine.

i notice it mostly when my cooling fans turn on, noticed it a whole lot during the winter while running the heater. I cant figure out what's causing the voltage drop which is dropping my idle.

kanine

Now that you mention that, yes, I noticed it too, right after the RPM drops the fans turn on. I don't have a Premium so no voltage guage, I'll have to check with a multimeter. Normal with car on should be around 14 I think, so 10 to 11 is a bit low. That sounds like it could be the battery or alternator, how long has yours been doing that?

DeeJayTJ

yep, 14 is what it should be. Mine has been doing that since about november of 2017.

I was thinking about the battery or alternator also.

Just to mention, I let it sit for 2 months and would start it each week just to let it run for a while, then yesterday i actually had to jump start it and the battery is only a year old. Though it has kept a charge since yesterday morning while ive been driving it for the last 2 days... so that might cancel out the alternator idea (atleast i hope) so maybe it could be the battery...

I dont have a premium either but i swapped the cluster and was definitely one of my favorite "mods" to my base gt.

SpectreH

It may also be a dirty throttle body. Easy to remove and clean.

DeeJayTJ

i watched my voltage gauge tonight, its now reading 13.7 even while driving. it used to be 13.9 all the time, until it would drop and idle rough for a few a second of course.

Gabe

It's normal to have an rpm dip and a voltage draw when the electric fan kicks in.
Mine does it too.


.

wanted33

Could you have some dirty injectors? They will cause the car you idle rough, and drop the rpm's. I'm old school, grab you some Marvel Mystery Oil, and run a tank full. It will clean anything. Just a thought. Good luck.

kanine

Yes, but not like this. It never started doing this till now, rpms dropping to 500 and shaking. I checked my battery, it is fine, around 12, with the car on, it goes up to 14, and then turning everything on, drops to 13.8 but goes back up, so that all seems normal.

kanine

That was one of the first things I did, cleaned the MAF and throttle body, cleaned it with the flap open too. It sort of "fixed" the idle for 2 days, but it went back to doing the same after. There was a little carbon build up, but wasn't that bad. I think I'm going to try some fuel system cleaner next, see if that does anything.

Gabe

Sounds like it might have a vacuum leak

Brian Trevino Aguirre

Experiencing something similar with 2014 5.0 71k miles, feel like car is being forced, happens mostly after a complete stop at yield lanes,stops,lights etc... i also noticed that when that happens cluster info such as speed,miles, gas,MPG turn off. Been trying to figured this out but not luck...

Bert

for weird electrical issues, first and simplest suspect is the battery -- if you are on the original battery it's about time to replace it so that's probably the first thing I would do

if that doesn't fix it I'd probably go to the dealer for a diagnostic

SpectreH

Manual or auto transmission?

Whyte50h

Hey Guys,

New here, I stumbled across this thread looking for the cure to this problem. I have a 2013 gt premium, 59k miles and it’s manual. Mine is idling low and jumping back up. I’ve checked the battery, alternator , I’ve checked for vacuum leaks, cleaned the maf sensor, put some some injector treatment in the tank but I do that from time to time anyways. Only thing I haven’t done is cleaned the throttle body really good. I never drive the car cause I work out of town so I haven’t burned through the tank of gas yet. Just curious if anyone found a fix?

Matt

SpectreH

Clean the throttle body.

Whyte50h

I'll do this when I get home Friday. Hoped I wouldn't have to do that, but I guess I'll take the time and pull it off and clean it good. I had just got my car back from getting it tuned and I thought it was that , but I put in an old tune I had from steeda and it still does it. I'll reply back and let y'all know if it helps. Thanks for replying!

Bert

I don't think you have to take the throttle body off; just remove the intake hose and be gentle when you open the butterflies

SpectreH

You don't have to remove it, but it isn't hard to do. Mine had the same idle issue plus occasionally stalling. Cleaning the TB cured it.

Whyte50h

Even better lol, thanks fella's, hopefully it'll solve the problem. I finally got it dyno'd and running like it should now this. Maybe this will be the trick!