[SimpleJack]

My car ('15 F36) has recently started to hard idle pretty significantly, and it's definitely getting worse. I first noticed an issue when I put on a BMS intake, but it was minuscule. Almost unnoticeable stutter on cold start and then no problems at all... well a few mods later (I will list them below), and my car is now losing power and stuttering between 1-2k rpm. On idle, it's almost like the engine is fighting to stay on (I'll post a video). I thought it could be a leak or loose intake so I checked it and it was slightly loose. I tightened it up but the problem remains.. in fact it's getting worse. I'll have my car in park at a stop light and the engine will jolt and stutter at or below 1k rpm. I just replaced the spark plugs about 4 months ago (NGK's gapped to 0.022). Again, it's really just between >1k-2.5k rpm. Car runs great at high rpms. My thought is it could be the intake, the coils, or a spark plug problem. Hope it's nothing worse.. the car only has 27k miles on it...any ideas?


Mods;
- BMS intake
- ER catted down pipe
- ER charge pipe
- ER TIC kit
- ER Competition FMIC
- BM3 91 oct Stage 2 tune

I'll post the video shortly... just need to link it

[SimpleJack]

Video of RPMs stuttering in park.

[thejeremyman9]

1. Scan for codes

2. Flash back to stock

3. Go back to stock intake

4. Pressure test for leaks

5. Check turbo inlet for cracks or leak

Check if problem remains between each of these. If still doing it,

6. Stock plugs stock gap

Did the problem start right after doing a mod or service? Both the BMS intake and the NGKs with small gap can contribute to poor idle.

Also post a log, WOT 4th is fine.

[alrocsmash]

Jeremy has the better troubleshooting ideas here but I would bet $100 it's your gap. I just swapped my plugs at .025 and it started hard. No codes. Googled this and many have issues there. I swapped to .030 and it went away.

[thejeremyman9]

Originally Posted by alrocsmash

Jeremy has the better troubleshooting ideas here but I would bet $100 it's your gap. I just swapped my plugs at .025 and it started hard. No codes. Googled this and many have issues there. I swapped to .030 and it went away.

If it happened after the plug change, i would 100% just go back to stock plugs. I was just listing stuff in order of increasing time/difficulty, starting with the easiest, if it was fine after the plug change but started later.

Also, running the colder plugs and smaller gap makes you more suceptible to plug fouling if you do lots of cold starts and take only short trips.

[harkes]

Never ever gap plug unless you have misfire issues. The advice is all over the internet and probably so hard to kill because ProTuning Freaks is advocating it on their website.

I think a lot of problems could be prevented if people kept to the old "dont fix it if it isn't broken" saying.

[alrocsmash]

Originally Posted by thejeremyman9

If it happened after the plug change, i would 100% just go back to stock plugs. I was just listing stuff in order of increasing time/difficulty, starting with the easiest, if it was fine after the plug change but started later.

Also, running the colder plugs and smaller gap makes you more suceptible to plug fouling if you do lots of cold starts and take only short trips.

Yeah, I have the NGKs now at stock gaps. No issues.

[SimpleJack]

Originally Posted by thejeremyman9

If it happened after the plug change, i would 100% just go back to stock plugs. I was just listing stuff in order of increasing time/difficulty, starting with the easiest, if it was fine after the plug change but started later.

Also, running the colder plugs and smaller gap makes you more suceptible to plug fouling if you do lots of cold starts and take only short trips.

That's a really good point.

Issues definitely started after plug swap, but I didn't notice it right away (probably a 2 month delay) but it became progressively worse. Though with covid, I'm barely driving at all. So absolutely a lot of cold starts and short trips.

I'll try gapping the NGKs to stock gap and see how that goes.

Thanks for the support.

[SimpleJack]

Originally Posted by thejeremyman9

1. Scan for codes

2. Flash back to stock

3. Go back to stock intake

4. Pressure test for leaks

5. Check turbo inlet for cracks or leak

Check if problem remains between each of these. If still doing it,

6. Stock plugs stock gap

Did the problem start right after doing a mod or service? Both the BMS intake and the NGKs with small gap can contribute to poor idle.

Also post a log, WOT 4th is fine.

So I flashed back to stock and the problem has almost gone away in its entirety. I still get minor to moderate engine stutters (in Park only) but I'm no longer losing power between 1k-2.5k rpms, and the car is no longer jerking forward when fully braked in drive.

Working on getting the logs.

[SimpleJack]

Here's a neutral log

https://www.bootmod3.net/log?id=603a...729b5a22ccf9c2


And stock tune idle

https://www.bootmod3.net/log?id=603a...90c671d1d6deb0

[thejeremyman9]

Originally Posted by SimpleJack

Here's a neutral log

https://www.bootmod3.net/log?id=603a...729b5a22ccf9c2


And stock tune idle

https://www.bootmod3.net/log?id=603a...90c671d1d6deb0

Its hard to gather anything from these especially because people dont usually post idle logs for comparison, but the thing that stands out is that your fuel trims are swining from min to max (+/-30%) in both directions. It looks to still be doing it to some extent on the stock tune.

I would try a WOT log on stock tune and one on stage 2 if everything seems safe.

Also try going back to stock intake and scan for codes (including shadow codes)

[tomzjack]

Originally Posted by SimpleJack

So I flashed back to stock and the problem has almost gone away in its entirety. I still get minor to moderate engine stutters (in Park only) but I'm no longer losing power between 1k-2.5k rpms, and the car is no longer jerking forward when fully braked in drive.

Working on getting the logs.

Hi, May i know how your vehicle recently ? is it solve the problem because i also have same situation like you now.

If yes, would you mind share more detail for the spark plug model that you are using.


Updated: changed from ECU to Spark plug wiring then problem solved


Thanks bro