Rough idle

[Virge]

My Mustang have a rough idle with a cold start. It does so especially with few gas in the tank.
I check the spark and it was smoke. I changed the spark but I'm not resolve the problem.
No engine light and no code/cel.
What could it be?
it could be a problem about EVAP purge valve? How can I check it?

My mustang is a 2017 Ecoboost stock

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[ronemca]

My Mustang have a rough idle with a cold start. It does so especially with few gas in the tank.
I check the spark and it was smoke. I changed the spark but I'm not resolve the problem.
No engine light and no code/cel.
What could it be?
it could be a problem about EVAP purge valve? How can I check it?

My mustang is a 2017 Ecoboost stock

Possible water in bottom of tank. Add a bottle of gas line anti-freeze (Methyl Hydrate).

 

[Virge]

Possible water in bottom of tank. Add a bottle of gas line anti-freeze (Methyl Hydrate).

the problem has been doing for months, I changed more gas stations, but nothing..

 

[TorqueMan]

My Mustang have a rough idle with a cold start. It does so especially with few gas in the tank.
I check the spark and it was smoke. I changed the spark but I'm not resolve the problem.
No engine light and no code/cel.
What could it be?
it could be a problem about EVAP purge valve? How can I check it?

My mustang is a 2017 Ecoboost stock

This doesn't sound like a malfunctioning EVAP purge valve. If your purge valve sticks open it can cause hard starts and rough running, but usually right after refueling. See this for more info:

https://www.samarins.com/glossary/purge-valve.html

 

[Virge]

Yesterday I tried to disconnect the hose from the purge valve, and closed both with tape.
Then I turned on the car, but I have the same issue..

 

[EcoBoostang]

I did a KAM reset and it resolved it temporarily but it's back, MPG isn't effected and its not stalling but it reminds me of my 68 mustang with a hot cam in it. It rocks the engine and the RPM flutters.

 

[BoosTang23T]

I had a bad fuel pressure sensor and vapour hose... The video below is what mine was doing. If it's the same behavior, have that checked out.

 

[nicolasfinta1]

I had a bad fuel pressure sensor and vapour hose... The video below is what mine was doing. If it's the same behavior, have that checked out.

Have the same issue did you find a solution

 

[BoostedNate]

Mine kind of does this but I'm manual and seems to be more noticeable when AC is on. It's typically only on a semi-cold, or warm start. PD Tuning has done a lot to improve it but I'd still like to know the cause.

 

[ctorres2332]

I had rough idle nothing like car wanting to shut off or anything like that. Just rough idling.

Didnt even knew i had rough idle because i import a salvage mustang and and repairing it the mechanic told me you have a ripped wire harness.

Turns out when checking it was a vacuum line that goes from drivers side to passenger side all the way down the car.

Replaced and car idling was normal.

Maybe check if you have a vacuumm leak in a hose.

There is a black vapor cannister right behind the air intake with two or three hoses one goes in drivers side other goes to passenger side.

You can identify the cannister it has like a tip pointing upwards.

 

[ctorres2332]

btw i never got an error code on the car.

 

[FreePenguin]

random, I also read and hear that a super free flowing exhaust can make an idle not 100% steady. I guess a little back pressure makes an idle nice and smooth, and when you chop all restrictions out, it can be 95% steady. not a miss or anything just not as smooth. but nothing like op experiencing

 

[BoostedNate]

I had rough idle nothing like car wanting to shut off or anything like that. Just rough idling.

Didnt even knew i had rough idle because i import a salvage mustang and and repairing it the mechanic told me you have a ripped wire harness.

Turns out when checking it was a vacuum line that goes from drivers side to passenger side all the way down the car.

Replaced and car idling was normal.

Maybe check if you have a vacuumm leak in a hose.

There is a black vapor cannister right behind the air intake with two or three hoses one goes in drivers side other goes to passenger side.

You can identify the cannister it has like a tip pointing upwards.

Are you talking about the evap purge valve? If so I replaced that about 2 years ago because the original was throwing a code. I recently enabled the evap can purge gauge % and I do notice that it drops to 0 when the idle drops. I’ve been trying to chase this for a while...
The issue isn’t present or as noticeable with AC off. It’s the most noticeable when I first turn on the car after it warms up and the idle RPM drops

 

[ctorres2332]

I noticed mine when idling because when i placed car in neutral and turned on RPM dropped. When replaced hose RPM stayed the same no matter is car was on D or N when stopped.
No code or anything it is a hose that was ripped in a collission. i replaced 6J005B on diagram, the cannister i mention is the one labeled as 6J005D

 

[BoostedNate]

I noticed mine when idling because when i placed car in neutral and turned on RPM dropped. When replaced hose RPM stayed the same no matter is car was on D or N when stopped.
No code or anything it is a hose that was ripped in a collission. i replaced 6J005B on diagram, the cannister i mention is the one labeled as 6J005D

Would it consistently drop or was it irregular? With mine it will drop for a few seconds and then go back up.

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