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      03-23-2020, 05:29 AM   #1
Yellowflash21
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Possible leaky fuel injector, looking for help

Having an idle issue on cold or when engine is warm.

It vibrates on every few seconds and rpm jump between 20-40.

When driving the car, car jerks between 1.2k and 2k rpm, in first and 2nd gear.

Everything above 2k rpm it works normal.

I believe that, that one of the fuel injectors is leaking very little and I think its number 4 after looking the logs.

Now, I'm looking to try to fix this by replacing it with the Bosh one, and I would like to know if fuel injector replacment requires re-calibration after the install?

Also, what are the torque specs for injectors and when replacing the spark plugs?

Thank you!

Here is the idle log:

https://datazap.me/u/yellowflash21/m...31&zoom=17-616

Last edited by Yellowflash21; 03-23-2020 at 08:25 AM..
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      03-24-2020, 04:36 PM   #2
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Quote:
Originally Posted by Yellowflash21 View Post
Having an idle issue on cold or when engine is warm.

It vibrates on every few seconds and rpm jump between 20-40.

When driving the car, car jerks between 1.2k and 2k rpm, in first and 2nd gear.

Everything above 2k rpm it works normal.

I believe that, that one of the fuel injectors is leaking very little and I think its number 4 after looking the logs.

Now, I'm looking to try to fix this by replacing it with the Bosh one, and I would like to know if fuel injector replacment requires re-calibration after the install?

Also, what are the torque specs for injectors and when replacing the spark plugs?

Thank you!

Here is the idle log:

https://datazap.me/u/yellowflash21/m...31&zoom=17-616
Get ISTA+ and run a diagnostics scan on your car would be the first step.

Next if it is the injectors ISTA will give you a step by step guide (including torque values) on what to do to replace it, and if injector coding is required ISTA will allow you to do so with the flow numbers or serial number that will be labeled on the injector.

Quick question, what makes you think it is an injector besides the rough idling?

Let me ask you another question do you have an aftermarket cold air intake? Because that did cause some issues for me awhile back on my m235i, some cars have a rougher idle and rough low rpm performance since it relies on the MAF sensor at those points, which is affected by a new intake.
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      03-24-2020, 05:22 PM   #3
Yellowflash21
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I've pushed the car on the empty highway and I've seen over 4 degree correction on cylinder number 4.

Regular oil and paper filter swap was done few weeks ago. So the intake is purely stock.
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      03-24-2020, 05:52 PM   #4
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Quote:
Originally Posted by Yellowflash21 View Post
I've pushed the car on the empty highway and I've seen over 4 degree correction on cylinder number 4.

Regular oil and paper filter swap was done few weeks ago. So the intake is purely stock.
I see. Is the car still under warranty? If so it's best to just take it to bmw since it will cost quite a bit.

If not then your first step is to get ISTA and an enet cable and run a diagnostics.
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      04-06-2020, 11:03 AM   #5
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Issue seems to be cause by too high octane fuel as I added small can of octane booster + 25 liters of premium fuel.

After adding 20 L of lower octane fuel, and driving for another 100 km. The issue is almost gone, and fuel trims are looking way better now.

There is still barely noticeable blip on low revs just in 1st gear while on idle it no longer chokes.

I will empty the tank, and refill with premium fuel.
Once that is done, I plan to change all plugs as it's right time and pre-cat sensor as well.

I didn't notice at first, but in logs you can see that LFTF was over 3% which means that engine was struggling to remove excessive fuel.

So please folks, don't pay with too many octane boosters, and I think the octane value in my case was bit over 105 or 108 octanes.
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      07-28-2021, 10:23 AM   #6
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I’m having the same issue. Rough cold start and slight stutter in idle(even warm). Shifting into first and second is bad. No misfire codes. I’m at 85k miles. I think I will do carbon cleaning and new injectors. Thoughts?


Quote:
Originally Posted by Yellowflash21 View Post
Issue seems to be cause by too high octane fuel as I added small can of octane booster + 25 liters of premium fuel.

After adding 20 L of lower octane fuel, and driving for another 100 km. The issue is almost gone, and fuel trims are looking way better now.

There is still barely noticeable blip on low revs just in 1st gear while on idle it no longer chokes.

I will empty the tank, and refill with premium fuel.
Once that is done, I plan to change all plugs as it's right time and pre-cat sensor as well.

I didn't notice at first, but in logs you can see that LFTF was over 3% which means that engine was struggling to remove excessive fuel.

So please folks, don't pay with too many octane boosters, and I think the octane value in my case was bit over 105 or 108 octanes.
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      06-08-2023, 07:09 PM   #7
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My car is completely stock, 32k miles 2017. Has the exact same issue as all of y’all. Slightly rev up at cold start then drop and stutter then rev back up and be normal. Only at cold start. Then when driving at low to med load and even with cruise control on at 2k rpm in 1/2/3rd gear and it will hiccup or jolt/stutter (whatever you want to say) and then continue and do it again and again when lightly accelerating or just cruising. Any advice? Injectors potentially?
From 50-WOT there is no issue and the car feels perfect. Any advice would be appreciated.
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