'14 Mirage DE Idle Fluctuation–Fuel Delivery Issue?

[Bennett15ify]

Hi, all!

I've recently acquired a '14 Mirage DE CVT with 109k miles. I am having an issue with idle fluctuation. See attached video:

https://youtube.com/shorts/OXTQDav2vPM

This occurs immediately after starting the car. The engine can be hot or cold, though the issue is more prevalent when cold. The fluctuation has been even more severe than in the video, though it doesn't affect drivability and goes away after about a minute. It's only noticeable at idle.

ADDITIONALLY, (hopefully, this is related) the car recently sat for two weeks; when I tried to start it, the motor turned over for 20+ secs. I eventually held my foot on the gas pedal and it did start. I haven't had a starting issue with it since but also haven't let it sit for that long either.

I know the spark plugs were changed within the last year. It's had a recent oil change. I also did the CVT filters and fluid, though I'm sure that has no sway on the idle issue.

Any ideas are welcome... thank you!

[klroger]

No Check Engine Light, Right??? Just for a goof, put a couple of tanks of fuel thru it with Techron Cleaner added. People have reported good luck with this as it will help clean the injectors & the back of the intake valves. Try it first & see..

[CROSSBOLT]

Intake leak between throttle body and engine?

[Top_Fuel]

Maybe consider cleaning the throttle body. It will only cost you some time and a $3 can of throttle body cleaner. Just be sure to read that thread closely if you decide to do it. Cleaning modern throttle bodies is a little different from cleaning the throttle body on a 20 year old car.

[mohammad]

I had a similar issue, new spark plugs appeared to fix it for me. im on my third set with under 100k, km so who knows. coulda just been magic

[7milesout]

I'm going to 2nd the throttle body cleaning. My 03 Camry had a dirty throttle body. The symptoms were different, but I could see a dirty throttle body causing that hunt. Just imagine, there's gunk built up on the body or the butterfly valve edges, or likely both. That gunk reduces the amount of air that is going to be able to pass by for idle purpose. That lack of air would tend to slow the engine. The ECU is programmed to hold a certain rpm, so the ECU would add throttle to counter the engine slowing. Adding throttle could cause a small rev. Then the ECU lets off the throttle because it revved past its set point. The lack of air around the butterfly starts the cycle again. It would totally depend on the ECU programming (idle gain) as to how this battle manifests.

In the case of my Camry, the rpm dropped below and the ECU (gain) was low enough it just stopped it from dropping even lower. That lower rpm must have put the engine at a speed that it didn't balance well in conjunction with the firing rate ... very complex, so that's just a guess. But the engine had more vibration than it should've. I looked at the throttle body and it was very gunked up. So I pulled it out and cleaned up real good with cleaner and a tooth brush. Put it back in and OH WHAT A DIFFERENCE. Smooth idle, no vibration and just off idle acceleration smoothed out real nice too.

I never ever ever put any kind of deposit cleaner in any vehicle tanks. Because they do just what they advertise. The clean gunk. Very effective stuff too. However they start cleaning in the tank, and that crap once loosened gets sent on down the line. To the injectors.

If I want/need injectors cleaned, they get removed and cleaned manually. Guys that run shops that clean fuel injectors think fuel injector cleaner that is added to the tank is the GREATEST thing ever. They get a lot of business due to that stuff.

[FreeYourSOUL]

Same problem here, it's my Mitsubishi Xpander. Throttle body and sparks plug are clean, updated the ECU's firmware, recalled the fuel pump but no result.
It's noticeable from exhaust sound and tachometer.

[Dirk Diggler]

I watched your vid are you sure there's even an issue? I remember my rpm needle slightly ticking up a cm at idle when the AC compressor kicked on.

[Fummins]

You can also just pump the brake pedal a bunch of times and it'll probably do the same thing.

[CROSSBOLT]

Same problem here, it's my Mitsubishi Xpander. Throttle body and sparks plug are clean, updated the ECU's firmware, recalled the fuel pump but no result.
It's noticeable from exhaust sound and tachometer.

What's the problem here? Tach needle stuck on 1000 rpm? The only significant noise I hear is when you move around. Should not idle that long. Bad for you. Drive it like you hate it 'til it breaks sumptin' the fix that. Next...