[driven72]

Hello Folks. Happy New Year.

I had a question about my car. I have a 2013 BMW 328i Xdrive Sportline F30, that has 74K miles.

I noticed a slight hesitation of the engine when idle today. Like dropping the RPM and then coming back up...but it almost felt like it was going to stall. It also had a slight hesitation when accelerating slightly and it felt like it was going to stall again but it then normalized. It drove fine for 30 min to our destination.

On my way back, it felt like it was going to stall at idle again. First time I am feeling this occur during idling. It's been relatively trouble free from the time I bought it used at 13k miles, certified, and have not had any major issues.

Everything is stock and nothing is modified on the car. The car has not been "pushed" or battered around. Relatively mild driving habits. All oil changes and maintenance done as per schedule.

However, I have seen some recent bulletins about a water pump connector recall and another issue with a timing chain to be replaced after 70k miles (which I think is utter nonsense to have to replace a timing chaing and spend 5K before 100k miles)

Lastly, no check engine lights or warnings on the screen(though it may pop up if it becomes more frequent).

There was however, a brief issue with the coolant dropping below min. two weeks ago. I took it to the BMW dealer and they said to top it off and that it may not be a concern. If I have not checked the coolant it could burn some coolant. I saw an error message that the coolant was low. It took only 2 cups (50/50 ratio distilled water and coolant) to get it back to max level. I took it to another shop and they changed the oil, performed a pressure check and found no leaks anywhere in the system.

Oh yeah..I have yet to replace any spark plugs for this car since ownership.

Has anyone else experienced this issue? Sorry in advance if this has been discussed on a previous post. Any advise or help would be appreciated.

I am wondering if it's time to trade this vehicle in before something major happens.

Cheers.

[fe7565]

Your description is detailed, but not enough IMHO to pint point anything specific.

How is your coolant level now after two weeks? If low again, you have issues.

If you have time, inclination, and planning to tinker with BMWs in the future, I would download ISTA+ (free) and buy a $10 ENET cable (Amazon/Ebay) and check for BMW hidden specific codes. This should guide you in the right direction.

ISTA+ is available in antoher thread, just ask for it.

As far as timing chain. Replacing the timing chain tensioner is a must. $60-80 (do not buy on EBay/Amazon the Chinese junk $30), buy from a dealer online or from FCP Euro etc. This replacement will give you peace of mind, less noise, and takes about 40mins -1 hour, easy DIY job, just getting to it is a bit hard due to space.

[driven72]

Originally Posted by fe7565

Your description is detailed, but not enough IMHO to pint point anything specific.

How is your coolant level now after two weeks? If low again, you have issues.

If you have time, inclination, and planning to tinker with BMWs in the future, I would download ISTA+ (free) and buy a $10 ENET cable (Amazon/Ebay) and check for BMW hidden specific codes. This should guide you in the right direction.

ISTA+ is available in antoher thread, just ask for it.

As far as timing chain. Replacing the timing chain tensioner is a must. $60-80 (do not buy on EBay/Amazon the Chinese junk $30), buy from a dealer online or from FCP Euro etc. This replacement will give you peace of mind, less noise, and takes about 40mins -1 hour, easy DIY job, just getting to it is a bit hard due to space.

Thanks for the response. Coolant level is fine. I am not sure what the level is when it's cold vs warm but I had filled it to the max line and the mechanic who checked it added more(At least I think he did since it was above the max). He said no issues with pressure.

Currently, I have a guy that is working on the car and he said the MAF was spotless..very clean. The spark plugs didn't have any build up but we replaced it anyway... but the PCV diaphragm was cracked. That was outlined in one of the posts. So I had him replace that. We didn't replace ignition coils as that would most certainly kick out an error code/check engine light.

I will get the car back today. He's currently testing it to see if there are any idling issues. I'll keep you all posted. Sort of frustrating to not have a root cause identified.

Ill ask the mechanic about the timing chain tensioner.

[fe7565]

Replacing the timing chain tensioner is a must for your model. It's the best insurance. I did my DIY. Was easy.

Looking forward to hear back once you got your car back.

[driven72]

Originally Posted by fe7565

Replacing the timing chain tensioner is a must for your model. It's the best insurance. I did my DIY. Was easy.

Looking forward to hear back once you got your car back.

Well I just got back. After replacing the parts, it still didn't fix it. So that definitely sucks. He thinks it may be the timing chain because it may be loose ONLY during idle because under load there are no issues.

I did tell him what you said about the timing chain tensioner and he thinks it could be an issue and if it's something he can do without tearing down the engine, then sure...he can do it.

I am really getting annoyed because out of ALL the comments and posts about this issue, no one seems to have a smoking gun or actual root cause. Like WTH? How can that be even possible?

Even the dealerships are saying it's the timing chain, and some guy had the dealership replace it and that STILL didn't fix the issue! Now they say it's something else. If this is so common, how is there no solution?

Anyway..I will give your suggestion a shot. What model year do you own? F30 I assume? From your profile you drive an N26. Is the design different from the N20 engine?

[fe7565]

I have a 2012 F30 328I N26. Tensioner is about $60-80. Get the genuine BMW, not the $30 EBay / Amazon.

By the way, the BMW timing chain replacement process includes the timing chain, the timing chain guide the tensioner, the oil pump assembly, including the oil pump chain.

[driven72]

Originally Posted by fe7565

I have a 2012 F30 328I N26. Tensioner is about $60-80. Get the genuine BMW, not the $30 EBay / Amazon.

By the way, the BMW timing chain replacement process includes the timing chain, the timing chain guide the tensioner, the oil pump assembly, including the oil pump chain.

Ok...but what is causing the engine hesitation. Is it the timing chain?

[fe7565]

Did your mechanic check with ISTA+ if there were any hidden errors? At this point the hesitation could be caused by many factors.

A stretched timing chain may cause timing issues, but I think you would hear a pronounced whining noise coming from it at increasing rpm’s. Did your mechanic check your timing with an oscope or ISTA+?

[driven72]

Originally Posted by fe7565

Did your mechanic check with ISTA+ if there were any hidden errors? At this point the hesitation could be caused by many factors.

A stretched timing chain may cause timing issues, but I think you would hear a pronounced whining noise coming from it at increasing rpm’s. Did your mechanic check your timing with an oscope or ISTA+?

No. He did not check it. However, there was no whining noise (at least not yet). Certainly no whining noise under load when driving over 30 mph or if the rpms are over 1000.

There is hesitation at accelerating at the start but it goes away when driving on the highway.

We checked the codes too and there was nothing related to timing chain issues or even any historically stored errors related to it. It was pretty clean from that perspective. I had another mechanic shop specialized in german cars tell me the same thing. They did the diagnostic for free but told me that the chain, according to the computer is meeting the spec in terms of being centered. (not sure how he was able to do it) they concluded that I should do the maintenance and replace the chain within 10k miles. However, they are charging way too much. around $6500 and they are not even a BMW dealership.

The mechanic I am working with now, is doing this on the side. He races Bimmers and works on them. Just bought a garage and has a lift. So he is prepared to do the timing chain replacement for half the cost when I am ready.

BTW...is there a video of what the whining noise sounds like?

[fe7565]

What I’m trying to say is that without that whining noise and no diagnosis of a timing chain issue you need to focus on something else. And the only way to find out what to focus on is to check the hidden BMW error codes, unless your mechanic has the ability to diagnose with an oscilloscope. And I’m not aware of any other easy way to check otherwise besides ISTA+, which is probably the best way to find out if there is an underlying issue

Regardless of what causing the hesitation, you must replace the timing chain tensioner if it’s original. There are numerous posts on this and there’s absolutely no way to get around it but to replace it. As far as replacing your entire timing chain and oil pump chain etc (as it is prescribed in the BMW bulletin ) if they are saying that you don’t have any guide or stretching issues then don’t replace it.

There are several threads over here where people post their whining, timing chain sound, or you can search on YouTube. But based on all you tell me you need to focus elsewhere for the problem.

Why don’t you post the other error codes? You said they are not relevant, well let others here look at them just for assurance.

Is the hesitation, persistent, does it happen every time you drive it? If not, it’s quite difficult to diagnose it without hooking up a device/laptop and taking real time readings, because a lot of these error codes eventually clear themselves out after a few restarts.

[driven72]

Originally Posted by fe7565

What I’m trying to say is that without that whining noise and no diagnosis of a timing chain issue you need to focus on something else. And the only way to find out what to focus on is to check the hidden BMW error codes, unless your mechanic has the ability to diagnose with an oscilloscope. And I’m not aware of any other easy way to check otherwise besides ISTA+, which is probably the best way to find out if there is an underlying issue

Regardless of what causing the hesitation, you must replace the timing chain tensioner if it’s original. There are numerous posts on this and there’s absolutely no way to get around it but to replace it. As far as replacing your entire timing chain and oil pump chain etc (as it is prescribed in the BMW bulletin ) if they are saying that you don’t have any guide or stretching issues then don’t replace it.

There are several threads over here where people post their whining, timing chain sound, or you can search on YouTube. But based on all you tell me you need to focus elsewhere for the problem.

Why don’t you post the other error codes? You said they are not relevant, well let others here look at them just for assurance.

Is the hesitation, persistent, does it happen every time you drive it? If not, it’s quite difficult to diagnose it without hooking up a device/laptop and taking real time readings, because a lot of these error codes eventually clear themselves out after a few restarts.

Yeah...the hesitation happens all the time at idle. I think it's gotten worse with the stalling. Before..it was rough idling for a split second...now it's rough idling and the auto start/stop ignition turns off and it seems to be ok but then it will stall out.

I can post the error codes. No problem. My mechanic can do the timing chain tensioner. I will look that up in the posts here to learn more about it.

What exactly is the issue with the tensioner and what are the symptoms? I don't want to take too much of your time...I can look it up. I appreciate all the info you have provide me so far. Much appreciated.

[driven72]

These are the error codes. I am not sure what ISTA+ is but this is what my friend sent me when he hooked it up to his laptop.

Info memory

Date: 1/8/25, 7:08P
VIN: WBA3B3C55DJ812259

10 Central Gateway Module
11 errors
101008: Non-resolvable ambiguous routing - SG not in the SVT target table
101010: SIF error
101012: TM Error
100600: Flexray protocol startup time is too high
100100: Contact to FZM slave lost
100101: Sleep confirmations are not complete
100104: HW Weckgrund ZGW
100300: Commissioning could not be carried out because TAS is already busy
100001: VcmResultSvtCheck - identity check: Differences between the SVT actual and
SVT target have been recognized.
100203: DM software error info warning
100204: Message monitoring: no system context signal

12 Digital Motor Electronics
5 errors
118001: Mixture control: Mixture too lean
11CF30: Mixture control: group error
1FB601: Check control message (ID 450): Auto Start Stop function deactivated

1

1FB601: Check control message (ID 450): Auto Start Stop function deactivated
138A11: Exhaust flap, plausibility: adjustment time implausible

19 Transfer box
1 error
440011: VSM_EVENT_VEHICLESTATE

1C Integrated Chassis Management
2 errors
482651: Slip angle estimator - inputs not valid SBS
482656: Slip angle estimator - internal degradation due to SBS

29 Dynamic stability control
1 error
480AB5: Transfer case long-term protection function requested from LMV

36 Combox multimedia
2 errors
B7F1B8: DisconnectByDeviceDriver
B7F1B7: BT Linkloss

40 Front electronic module
2 errors
804029: NVM_QUEUE_EEPROM

2

93071F: Outgoing error message buffer is full

56 Roof function center
1 error
801A20: CAN_E_TIMEOUT

60 Instrument panel
3 errors
E12C2F: Interface HU (acknowledgment request combination, 0x172): signal faulty
E12C30: Interface HU (Status Service Call TeleX, 0x30F): signal faulty
B7F6DE: APIX communication error counter during startup

61 Combox emergency call
2 errors
61A003: SIM card not unlocked
619400: VSM_EVENT_VEHICLESTATE

63 Headunit Basis
1 error
101712: A PIA function will report its configuration information even though it has not been
prompted for it

72 Rear electronic module
3 errors
8049E5: CNM_E_NETWORK_TIMEOUT

[fe7565]

The tensioner was redesigned after 2015, and received a stronger spring, longer plunger, and new oil port-hole locations. The old tensioner allowed the chain to have too much slack and that beat the guides to death and they eventually shattered and were ingested into the engine and oil cavities.

BMW agreed to replace the timing chain and oil pump with extended warranties. This is just of of many notices that are/were applicable based on the car's original registration date and state of registration: /https://static.nhtsa.gov/odi/tsbs/2021/MC-10204534-9999.pdf

===========================================

Now, as far as your error codes. I am not a mechanic, only a random DIY guy, but your mechanic cannot tell me that these errors are irrelevant to your idle and hesitation and stall.

First, are these codes recurring? I see these many error codes after a battery fail (different codes) or after the replacement of an ECU etc., or disconnecting vital connectors. Normally, when you use ISTA+ to delete all error codes, you should have most of these, if not all, go away. But if these codes are PERSISTENT, then you have issues. And many...


Your car's "director of operations" for all ECUs, the Central Gateway Module (ZGW ) and DME have either configuration errors, and/or there is a wrong part installed, or a part that was never configured to work with your car. You have HW (hardware) error, flexray error (network), SVT Actual and SVT target (misconfigured FA), etc. Basically, your car seems to have been retrofitted with non-original part(s) or part(s) were replaced and not properly coded to your car.


There is a lean mixture code that may or may not be the symptom of something else wrong and maybe putting the DME into minimalist mode. A lean mixture can lead to stalling and hesitation, etc

Also, there may be a "limp mode" issue where the car puts certain systems into a cripple-mode and they operate only at their very basic minimum parameters not responsive to changing power/etc requirements. https://x3.xbimmers.com/forums/showthread.php?t=1743471&page=2

How old is your battery? Is it registered properly? Does your battery run down often? What is your battery voltage when engine is not running and when engine is running?

[driven72]

Originally Posted by fe7565

The tensioner was redesigned after 2015, and received a stronger spring, longer plunger, and new oil port-hole locations. The old tensioner allowed the chain to have too much slack and that beat the guides to death and they eventually shattered and were ingested into the engine and oil cavities.

BMW agreed to replace the timing chain and oil pump with extended warranties. This is just of of many notices that are/were applicable based on the car's original registration date and state of registration: /https://static.nhtsa.gov/odi/tsbs/2021/MC-10204534-9999.pdf

===========================================

Now, as far as your error codes. I am not a mechanic, only a random DIY guy, but your mechanic cannot tell me that these errors are irrelevant to your idle and hesitation and stall.

First, are these codes recurring? I see these many error codes after a battery fail (different codes) or after the replacement of an ECU etc., or disconnecting vital connectors. Normally, when you use ISTA+ to delete all error codes, you should have most of these, if not all, go away. But if these codes are PERSISTENT, then you have issues. And many...


Your car's "director of operations" for all ECUs, the Central Gateway Module (ZGW ) and DME have either configuration errors, and/or there is a wrong part installed, or a part that was never configured to work with your car. You have HW (hardware) error, flexray error (network), SVT Actual and SVT target (misconfigured FA), etc. Basically, your car seems to have been retrofitted with non-original part(s) or part(s) were replaced and not properly coded to your car.


There is a lean mixture code that may or may not be the symptom of something else wrong and maybe putting the DME into minimalist mode. A lean mixture can lead to stalling and hesitation, etc

Also, there may be a "limp mode" issue where the car puts certain systems into a cripple-mode and they operate only at their very basic minimum parameters not responsive to changing power/etc requirements. https://x3.xbimmers.com/forums/showt...1743471&page=2

How old is your battery? Is it registered properly? Does your battery run down often? What is your battery voltage when engine is not running and when engine is running?

Oh my. That's a lot of info. I can't think of anything I could have done differently. The first 4 years of ownership, I took it to the dealership for all servicing but mostly oil changes. It was also a CPO vehicle so bought it used with only 16k miles from a BMW dealership. It was 3 years old so I can't imagine any aftermarket parts being put on so early with such less miles.

I do my own brake pads and rotors and I don't think I have done anything else on the car this whole time. The dealer did a full flush but that was the only thing we had done in all these years. We hardly drove the car during covid time frame so it just sat in the garage.

I have only been having issues now. The spark plug replacement, PCV diaphragm, engine air filter, and cleaning the MAF, are the only things I did a couple days ago. Otherwise, everything has been original.

Now, TBH, the battery may be original. I can't seem to remember. I am asking my other mechanic to see if I ever replaced the battery and had it registered. I thought I did....but not sure.

Someone posted in the forum that he replaced the battery and the hesitation went away...I didn't believe him. That said, I would get some sort of warning light if my battery had an issue?

Now regarding the mechanic, I need to clarify. The mechanic that just replaced my spark plugs and everything else does not have the error code output. He is a new guy and someone my friend and I know.

My friend owns an N55 335i. He does all his work. Does the coding, optimization, etc. He provided the error codes I posted above. He briefly looked at the output and he said nothing really stuck out. In fact I don't remember seeing the "mixture lean" error code. We may have overlooked it.

The 2nd round of checks was done by another mechanic shop for free...but they didn't mention any issues with the codes either. I have attached their diagnostics. I am not sure if they are the same as what my friend found. I will double check.

Really appreciate the education here. There's so much to learn. Sheesh. I just want the darn thing to run. LOL!!!

[fe7565]

Yes, I don’t see any relevant error codes in the second set of errors you posted just now. I believe the error codes you have now could be fixed with Bimmercode or some other program like Esys. But that’s for another topic.

I noticed that these errors were scanned with an Autel machine. Which may or may not be a very sophisticated machine, but I think because of the issues you’re having the best thing would be to diagnose your vehicle with ISTA+ and a $10 ENET cable you can buy on Amazon or eBay.

You can get ISTA+ for free on this forum in another thread, just request it. If you are planning to do some work on the car on your own in the future, it’s a worthwhile effort. It shows error codes that are specific to BMW that may not be detected by third-party code readers. ISTA+ is also the same exact software that is used by every BMW dealership around the world. And it does offer self-diagnostics, resetting systems, reinitializing, and recalibrating systems, in addition to all wiring diagrams.

It will read all your error codes, give you an option to delete them all, and if any of them come back, it will give you a step-by-step plan on how to resolve them.

[driven72]

Well...I talked with another BMW dealer. This time it was another BMW owner at work who has spent a lot of money on his maintenance and he gave me his mechanic to talk about the issues I am having.

It's just weird. He just said that the stalling is not a problem if there are no error codes. He said the F30s are completely software based systems and you can't even adjust the idle separately even if you wanted to. If there are no check engine lights coming on or any other problems, then it's just trial and error at that point. He recommended putting in sport mode to see if anything changes. ( I typically drive comfort or econ) However, it changed nothing. Still stalls in sport mode.

I don't get it. Anytime there are issues like this, there should be a fault tree analysis and list of root causes.

He did say that he didn't think it's tied to the timing chain issue. He recommended that I change the timing chain as maintenance because it's just a matter of time before it fails. Suggested I take the oil cap off and look at the plastic guard to see if there is any wear.

He wouldn't comment on the timing chain tensioner redesign. He didn't know about it or sometimes BMW keeps them in the dark on that stuff. If I replace the timing chain, hopefully they made design changes, I definitely do not want to do it every 75K miles. That's ridiculous.

He will do a deeper dive diagnostic for $230. The cost to replace the timing chain is $6k. My other mechanic will do the whole job for 3K with timing chain kits.

[fe7565]

As I mentioned, considering that you have no detectable issues with your timing chain, the focus should be on something else.

The chain tensioner replacement, which I did myself in 45 minutes and cost me $80 is a preventive measure. The tensioner has been redesigned, there are threads on this here with photos, there is also a different part number for the new tensioner. Once you replaced the tensioner and you had no other issues with the timing chain or guide prior to it, you should not have to do anything else, as the odds of failing will be the same as any other vehicles that were made after 2015 when they redesigned the timing chain tensioner. And to my understanding, failure of the timing chain for 2015 and later models is not frequent.

But this will not fix your idle issue and your hesitation. Anybody who is telling you that hesitation and near stalls are normal is wrong. If it would be normal, BMW would not sell many vehicles. And I’m quite sure that I have seen an idle adjustment option in ISTA+, although it’s true that it’s run by the computer. But adjusting the idol obviously will not fix your stalls and hesitation issues, because something is causing them.

I can’t tell you what you should spend your money on, and in a perfect world replacing your entire timing chain and oil pump/chain is a smart thing to do. But since there’s no indication that you have timing chain Guide damage or stretching you may want to spend your $3k ot $6k on something else (If you don’t want to DIY), like finding the cause of the hesitation and stalls. Maybe the mechanic can drive it (so he can experience himself that it’s not a normal occurrence) since you mentioned that it happens every time.

By the way, the timing chain issue is the most well-known issue with F30 car engines. There are several bulletins on this from BMW as part of a class action lawsuit settlement. I’m surprised that the mechanic is unaware of the changes made to alleviate this issue with production cars made after 2015. I recommend, if you are really interested, and you want to make a reasoned decision yourself, to search online this particular topic. The BMW bulletin outlines a step-by-step diagnostic of the timing chain and the oil pump chain which has to be performed by the dealer. The dealer uses a special device connected to several sensors to determine if your timing chain is stretched. This task can also be done in ISTA+ without a special tool, but will not work for every vehicle. As I mentioned before, there are some states where this is still covered under the extended warranty/class action lawsuit.

But let me emphasize again, the source of your hesitations and stalls by all indication are not related to your timing chain.

[fe7565]

[fe7565]

Here’s a procedure using ISTA+ to determine if you have a stretched timing chain. I was not able to do this with my car as it needs for some reason, the external testing module with sensors, but in some cars it may work.

[keithyo88]

I bought an old Audi and am chasing an oil leak. 3 different professional mechanics had different opinions on how to approach things. Of course each approach costs money and may not even fix things. Amounts to a chance to test own judgement, which I usually get wrong

[driven72]

Originally Posted by fe7565

Here’s a procedure using ISTA+ to determine if you have a stretched timing chain. I was not able to do this with my car as it needs for some reason, the external testing module with sensors, but in some cars it may work.

This is great info! Thanks so much. I will talk to my mechanic. I am a bit apprehensive about him doing the timing chain replacement but he could probably do the timing tensioner.

I will look through your other comments. Thanks again for helping out. Means a lot.

[driven72]

Originally Posted by fe7565

As I mentioned, considering that you have no detectable issues with your timing chain, the focus should be on something else.

The chain tensioner replacement, which I did myself in 45 minutes and cost me $80 is a preventive measure. The tensioner has been redesigned, there are threads on this here with photos, there is also a different part number for the new tensioner. Once you replaced the tensioner and you had no other issues with the timing chain or guide prior to it, you should not have to do anything else, as the odds of failing will be the same as any other vehicles that were made after 2015 when they redesigned the timing chain tensioner. And to my understanding, failure of the timing chain for 2015 and later models is not frequent.

But this will not fix your idle issue and your hesitation. Anybody who is telling you that hesitation and near stalls are normal is wrong. If it would be normal, BMW would not sell many vehicles. And I’m quite sure that I have seen an idle adjustment option in ISTA+, although it’s true that it’s run by the computer. But adjusting the idol obviously will not fix your stalls and hesitation issues, because something is causing them.

I can’t tell you what you should spend your money on, and in a perfect world replacing your entire timing chain and oil pump/chain is a smart thing to do. But since there’s no indication that you have timing chain Guide damage or stretching you may want to spend your $3k ot $6k on something else (If you don’t want to DIY), like finding the cause of the hesitation and stalls. Maybe the mechanic can drive it (so he can experience himself that it’s not a normal occurrence) since you mentioned that it happens every time.

By the way, the timing chain issue is the most well-known issue with F30 car engines. There are several bulletins on this from BMW as part of a class action lawsuit settlement. I’m surprised that the mechanic is unaware of the changes made to alleviate this issue with production cars made after 2015. I recommend, if you are really interested, and you want to make a reasoned decision yourself, to search online this particular topic. The BMW bulletin outlines a step-by-step diagnostic of the timing chain and the oil pump chain which has to be performed by the dealer. The dealer uses a special device connected to several sensors to determine if your timing chain is stretched. This task can also be done in ISTA+ without a special tool, but will not work for every vehicle. As I mentioned before, there are some states where this is still covered under the extended warranty/class action lawsuit.

But let me emphasize again, the source of your hesitations and stalls by all indication are not related to your timing chain.

So I finally got some time to start going through some stuff. I did open up the oil cap and didn't find anything wrong with the timing chain guide...at least not in the view I could see. I am not sure what it looks like without a borescope but I am thinking the diagnostic the other folks did at Mechanic One must be good and the timing chain is not stretched. (for now)

However, regarding your timing chain tensioner, I am not sure how this would go on. You say it only took 45 min but I can't find any youtube videos showing how to do this.

I did look up the forum and found people discussing this replacement and the costs but again, no pictures or videos on how this is done. Additionally, the chain needs to be held in place before un torquing so the chain does not skip a tooth? Some redditors are discussing the same issue and talking about a chain tensioner measuring tool to ensure the installation is good? Yikes!! sounds scary.

I wonder how much it would cost someone to do this job after I buy the part.