Idle issues

[EmCel]

Hi, not sure if this is the correct spot to post this but I need advice on a idle issue I’m having. Would appreciate it if someone can give me some advice on what to do or replace.

When I start my car the rpm is usually between 800-1000 rpm then a few seconds later goes up to 2k rpm then a second or two later drops down again. I’ve seen it low as 500 rpm where it felt like car was going to shut off. It constantly goes up and down when I start it. Driving the car is fine and all but like start ups and stop lights it feels like the car is just going to shut off because the rpm is so low.

The air/fuel ratio constantly goes up and down which I recorded today. I recorded two different videos, one showing my rpm going up and down and other one showing air/fuel ratio. I haven’t taken it to the mechanic yet. I called one but they said without codes they would need to do a bunch of diagnosis. I did have maintenance done on my car about a month ago where the guy replaced my spark plugs, serp belt, flushed the coolant & trans fluid. This rpm issue was happening before but it’s gotten worse seems like. I would take it to him again but I don’t talk to him anymore so just trying to see if anyone here can give me any advice on what I should even tell a mechanic to replace or to do even. Thanks

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[njweatherman]

When was the last time your mass air sensor and throttle body were cleaned?

 

[EmCel]

I haven’t done those. These were the only major things I’ve done so far besides regular oil changes.

 

[shogun32]

here's a capture from LiveLink of the first 60 seconds. Does anyone see anything seriously amiss? @Wengerd Performance ?
car is '16, no mods, no codes, stock tune. Only notable item not mentioned above is the fuel pump had been replaced about a year ago.

The F/A ratio is unsteady, going back and forth 14 +/- 2 in a slow wave, over and over and over. RPMs similarly track the F/A gyrations.
If there are PIDs I need to select and datalog once more, just say the word.

engine trace

 

[Cobra Jet]

The first (2) things I can think of, which are the most common Coyote idle culprits:
- The IMRC intake issues.
- The VCT issues.

Both will cause idle issues, both will not always throw codes unless there is a complete failure of the functional component.

Check the IMRC articulation shaft. In this thread, another M6G member repaired the broken IMRC shaft using JB Weld and it was fully functional again after the repair.
https://www.mustang6g.com/forums/threads/our-first-dtc-p0308.160243/

99% of the time, the IMRC failures are due to the broken shaft. Looking at images of the shaft, the break is occurring because the diameter of the shaft is too small for the torque being applied by constant activation.

—
VCT issues:
The VCT solenoids - operational issues can happen at any time. Usually debris gets into the solenoid which could cause idle stumbles. Changing oil can flush out the debris or the Ford Service Center has a procedure that will flush out the VCTs without an oil change. I don't think a Service Center will do this voluntarily, only if a VCT code exists. I’m also not sure if there is a way to use Forscan to do a similar “flush” as a Tech @ Ford would using IDS.

Here's (2) threads for VCT info that I had previously posted in other threads:
https://www.mustang6g.com/forums/threads/2015-2021-s550-5-0’s-ssm-50067-vct’s-again-various-dtc-codes.169419/

https://www.mustang6g.com/forums/threads/p0018-code.123932/

 

[EmCel]

Thank you @Cobra Jet

 

[nustang]

also possible loose intake pipe at throttle body. happened to me, loose band clamp. thats easy to check,

then what he said - lol.

 

[Bitten in '69]

Since you recently had work done, I would start with the basics, which you can do. Under the hood, divide the area into sections. Go through each area bit by bit checking the connections in the wire loom. It is possible that something has vibrated loose. It could also be a connector that was left undone after the job on the plugs.
It may not turn up anything, but the only cost is a bit of time.

 

[EmCel]

Thank you @nustang and @Bitten in '69 Appreciate it!

 

[Cobra Jet]

Since you recently had work done, I would start with the basics, which you can do. Under the hood, divide the area into sections. Go through each area bit by bit checking the connections in the wire loom. It is possible that something has vibrated loose. It could also be a connector that was left undone after the job on the plugs.
It may not turn up anything, but the only cost is a bit of time.

OoOoOo….. speaking of connectors, I did forget one thing even though you’re not getting a specific code (yet), or maybe not even a misfire - make sure the crank sensor connector is secure. That’s another known common hot spot on a 5.0 Coyote…. See here:

A faulty crank sensor OR one with loose wire contacts in the actual connector, which will also cause sporadic "random misfire" events. Other M6G members have found that the P0300 was related to a faulty crank sensor. Review each thread carefully because each owner came across it in a different manner.

Check this thread:
https://www.mustang6g.com/forums/threads/misfire-at-high-rpm.174380/#post-3531453

AND this one:
https://www.mustang6g.com/forums/th...e-sensor-tone-ring.156234/page-2#post-3197692

I don’t think that is your issue, but just throwing it out there - as this and the (2) prior mentions are THE most common Coyote 5.0 culprits for idle/drivability issues.

 

[EmCel]

Thanks guys! @Cobra Jet thank you again.

 

[EmCel]

Alright so @shogun32 and I cleaned the mass air flow sensor, throttle body, tightened the band clamps for the intake, and also put the air box cover on properly because it wasn’t on right. I started the car and the rpm is below 1k I wanna say like 750-850 range which is good, it wasn’t jumping up and down. The air/fuel ratio still has some play but it’s staying around 14 and a little over 14. So I will know for sure if all this worked tomorrow morning once the car sits for a while and kind of like a cold start. That’s usually when the rpm problems occur.

So thanks to you guys that replied, we tried the simple things for now.

 

[Cobra Jet]

Alright so @shogun32 and I cleaned the mass air flow sensor, throttle body, tightened the band clamps for the intake, and also put the air box cover on properly because it wasn’t on right. I started the car and the rpm is below 1k I wanna say like 750-850 range which is good, it wasn’t jumping up and down. The air/fuel ratio still has some play but it’s staying around 14 and a little over 14. So I will know for sure if all this worked tomorrow morning once the car sits for a while and kind of like a cold start. That’s usually when the rpm problems occur.

So thanks to you guys that replied, we tried the simple things for now.

Sounds good!!! Always a great strategy to work in that manner starting with the basics - and @shogun32 is a very helpful M6G member.

 

[Red65]

How many miles on the car? If it's over 50-60k, I highly recommend changing the MAF sensor if all your intake connections seem to seal fine. I had some real idle hunting / near-stall low rpm when stopping at stop signs and after a new MAF sensor, it's working properly.

 

[EmCel]

Ok I will do that too. I have like 80K+

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