5.0 Rough Idle issues

[Ayee__Jay]

Hey guys, for months my car has been randomly giving me drops in idles at red lights. Seems to happen more often when I’m especially driving in sports mode and at one time the car actually stalled on me. Rpms will drop and then go back to normal sometimes even shakes the car but then back to normal. I took it to the dealership this is gonna be the 3rd time and they changed the “driver side” vct solenoid (only 1, why? I dont know) and its still acting up. Has anyone had this problem and FOUND the solution?

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[Cory S]

Sound like a gasket/vacuum leak somewhere......

 

[Mustangmatty]

I have the same problem but have not taken it in yet. Usually happens in track mode for me at red lights. Annoying.

 

[Dfeeds]

Could be gas. I had this problem my first six months of ownership and was consistently filling up at one exxon mobil that's on my way to work (high traffic, top tier). Didn't think much of it but later started filling up at a shell much closer to my house and the issue went away. Since then I've filled up at a few different BP and shell stations without issue. I then tried filling up at that mobil again (about a year later) because it was significantly cheaper than shell and within two days the problem returned.

 

[K4fxd]

Mine was doing this. Cleaning the fuel injectors fixed it.

 

[Ayee__Jay]

I will add that it doesn’t happen immediately but after the car warms up and depending for how long i drive it and how i drive it if that makes sense

 

[mindo389]

Mine is a '15, same issue. Turned out to be bad gas. I bought a large can of seafoam and a Shell 93 octane fill up. A few floor board runs that night on an open interstate cleared it up.

 

[K4fxd]

Mine would just randomly drop 50 to 100 rpm then settle back to normal. Drove me nuts.

 

[Jackson1320]

Codes?

 

[ice445]

This a lot of times is the result of cam phasers/VCT solenoids. It's hard to diagnose though, you need a decent scan tool to watch how well the cam angle is controlled at steady state idle.

 

[19gtMD]

Im supercharged and my car does this idle jumping too. I thought it was the tune. I tend to get gas from one of two places so I'll try a shell station.on the next fill up

 

[Ayee__Jay]

Codes?

No Codes

 

[Ayee__Jay]

Im supercharged and my car does this idle jumping too. I thought it was the tune. I tend to get gas from one of two places so I'll try a shell station.on the next fill up

So I took it back up to the dealership and my tank was almost on E so they made me go fill up at least half a tank in which I went to some random gas station and filled up. Since I took it, they still couldn't find a problem BUT they also couldn't get it to act up with the idle like it has been doing. I got the car back and tbh I've been testing it to see if it will do it and nothing. So maybe I've been filling up at the wrong pump for months? (I consistently go to a certain gas station majority of the time) but its only been the weekend since I've had the car back so I'll see how it goes.

 

[Whitedevil95]

This is not the widely known Gen 3 Cam Phaser Issue?

I fail to see how "Bad Gas" can cause an INCONSISTENT low idle issue. If the gas was truly bad it would be a rough idle at all times.

 

[Cory S]

So I took it back up to the dealership and my tank was almost on E so they made me go fill up at least half a tank in which I went to some random gas station and filled up. Since I took it, they still couldn't find a problem BUT they also couldn't get it to act up with the idle like it has been doing. I got the car back and tbh I've been testing it to see if it will do it and nothing. So maybe I've been filling up at the wrong pump for months? (I consistently go to a certain gas station majority of the time) but its only been the weekend since I've had the car back so I'll see how it goes.

Most 91-93 octane pumps pull water these days. Only about 1-2-% of the country uses premium grade fuel. It sits in the tanks for months vs. 87.

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