Hard to Start

[roundy]

Morning all!

 

The last couple of days my 06 RT has been a struggle to start (it has been uber cold here in the UK) - have to give it some throttle to get it going but its fine once started.

 

Any pointers? She is due a service but can't imagine the valves are that bad?? Anything I can check with my GS911 ?

 

Incidentally (as my bike has been running rough and I took her off the road to install new suspension), since having my injectors serviced it seems to be running much better :-)

[dirtrider]

Morning Roundy

 

Giving it a bit of throttle to start is normal in very cold conditions. (how cold was it at starting)

 

Your riders manual has some cold starting info in it about holding throttle open a bit for very cold starting.

 

Have you done a fresh TPS re-learn since the last time the battery was disconnected?

 

 

[roundy]

Was maybe 0/1 Celsius...?

 

Hadn't done the TPS re-learn yesterday but did so before I started the bike this AM. (ignition on, cycle throttle 3 times, ignition off, back in and start)

[dirtrider]

Was maybe 0/1 Celsius...?

 

Hadn't done the TPS re-learn yesterday but did so before I started the bike this AM. (ignition on, cycle throttle 3 times, ignition off, back in and start)

 

Morning Roundy

 

How did it start after the TPS relearn?

 

To do the TPS re-learn correctly you really need to do a battery disconnect for a few minutes before the key-on throttle cycle.

[roundy]

It did the same start, needed some throttle.

 

Will try another re-learn when I get home.

[dirtrider]

Morning Roundy

 

Yes do a new (battery disconnect first) TPS re-learn. Then see how it starts.

 

You might wait & see how it starts when it warms up a little. If it starts with no throttle when a little warmer then probably nothing wrong with the bike.

[lkraus]

As D.R. said, this is normal behavior. From the owners manual: "At extremely low temperatures it may be necessary to operate the throttle twist grip during starting. At ambient temperatures below 32°F (0 °C), actuate the clutch after switching on the ignition."

 

For my '06 RT, slightly opening the throttle helps starting at any temperature under 40ºF (4ºC).

[roundy]

Ahhh, thanks for the clarification!

[roundy]

So I serviced the RT over the weekend and still having the same problem, won't start unless I give her throttle on start, was defo above 4 degrees this AM!

 

To be honest also I've never had this issue before, even in the depths of winter!?

[dirtrider]

Afternoon Roundy

 

I really don't know what to tell you on the cold starting issue.

 

If it isn't the cold weather then it might be a stepper reset issue if it starts OK with a little throttle.

 

Did you do the TPS re-set? If not start there.

 

Also, try turning the key ON, then waiting until the dash does it's full boot sequence before trying to start it. (maybe do this twice before pushing the start button). This allows time for the steppers to go completely through their homing process.

[roundy]

Hey DR, disconnected the battery overnight and did a TPS reset this AM - I also reset the steppers before I did the battery pull.

 

(One of my main drives for the ECU wipe overnight was that she's been running awful again.)

 

Started this AM without any additional throttle, and (most likely because of the ECU reset) ran great up until I hit town and traffic. Stalled on coming to a halt after blip'ing the throttle too! Idle just seems to be horrendous at the moment, can't understand why. Will see how the start is tonight when I leave work.

 

I did have a look at the O2 values last night and watched them plotting. What did confuse me was that they were well above and below the lean/rich markings on the GS-911 graph. Also, you can see one cylinder not matching the other throughout the plot. I did take a CSV export of the values so i'll post that up when I get home.

 

The other night when I got home I pulled the left side coil pack and you know what I am not sure I could notice a difference, or if there was it was very small. Wondering if I need to bite thee bullet and get a blank canvas with some new coils.

[dirtrider]

afternoon Roundy

 

The steppers automatically re-set at key-on so no real gain in doing it with the GS-911.

 

Your problem is pointing more & more towards either a bad o2 sensor or a bad stick coil.

 

If your starting problem goes away (every time) with a battery disconnect for 30 minutes or more & then a new TPS relearn that more points to bad o2 than to a stick coil.

[roundy]

Ok, will see what happens when I leave the office.

 

If I have the starting issue tonight I'll do a battery disconnect when I get home and see what happens.

 

Why would a bad o2 sensor be causing this? Can I disconnect them and see if its better?

[dirtrider]

 

Why would a bad o2 sensor be causing this? Can I disconnect them and see if its better?

 

Afternoon Roundy

 

The bad o2 causes a fueling learning off-set that it remembers until the battery is disconnected or it re-learns correct info.

 

Yes, you can try disconnecting the o2 sensors, just be VERY CAREFUL as the little connectors are very fragile & break easily.

[roundy]

Went out to the bike this AM and couldn't start without some throttle. Got the battery disconnected now and will pop back out there this evening to update!

[roundy]

Weird, this afternoon I reconnected the battery and did a TPS reset - wouldn't start without throttle :-S

 

Really confused now!

 

Attached is a log I grabbed the other night when arriving home from work - not sure if it gives any clues...?

 

https://dl.dropboxusercontent.com/u/46259303/log%202015-03-19.csv

[dirtrider]

Morning Roundy

 

You problem might be in the .csv data, unfortunately I am on the road with only my old lap top & the old Excel I have opens the data in a very garbled form.

 

When I get to a computer that can properly open the .csv I will look at it for you.

 

In the mean time if you are in a hurry you might PM that .csv to Roger to see if he can spot an issue.

[dirtrider]

Weird, this afternoon I reconnected the battery and did a TPS reset - wouldn't start without throttle :-S

 

Really confused now!

 

Attached is a log I grabbed the other night when arriving home from work - not sure if it gives any clues...?

 

Afternoon Roundy

 

I got your .csv to work & looked at the data, no smoking gun on the data so--- can you get me another data grab but this time get it at overnight-cold-soak cold start. (basically just a cold start after an overnight parking)

[roundy]

Will do! How long shall I log for?

[dirtrider]

Afternoon Roundy

 

A minute should show us what we need.

[roger 04 rt]

Afternoon Roundy

 

A minute should show us what we need.

 

Good Afternoon DR,

I agree with getting a cold start log.

 

One thing that stands out in the data in the CSV file that Roudy posted is that Lambda Control Factor 1 and Lambda Sensor Voltage 1 are running very differently from the #2 side. I believe #1 is Right and #2 is Left cylinder.

 

What I see in the first 50 or so data points is the Lambda Sensor Voltage looking very Lean, and then I see the BMSK ramping the Lambda Control Factor to 25% rich. Then over the next 50 or so points, the LCF1 comes back down to no added fuel (about 1.00).

 

It is possible that for some reason cylinder 1 is very lean at start up. It will take more tests to confirm.

 

Otherwise, the log looks good. Every sensor and the BMSK seems to be doing its job.

[dirtrider]

Afternoon Roger

 

I pretty sure the BMK-S doesn't fuel to the o2's until they start toggling. You can see the lambda control factor start responding about line 36 or so.

[roger 04 rt]

Evening DR,

As soon as the impedance of the O2 sensor drops the BMSK starts using it as a fueling reference. You can see sensor voltage 1 go low, and in response the BMSK starts increasing lambda control factor 1. LCF1 eventually reaches 25% and then starts to co down, not normal.

[roundy]

Took the car into work today guys so RT will be nice and "cold start" when I get home, will grab some more logs from cold start then.

[roger 04 rt]

Here is the picture (below) of what I'm seeing with the Lambda Sensor Voltage (LSV) and Lambda Control Factor (LCF).

 

The LSV lines show the actual, realtime voltage produced by the O2 sensor as the engine warms up. The LCF lines show what the BMSK has to do to get the calculated-fuel-pulse (which is about 2 mS after starting, while idling) into a range where the fueling meets the O2 sensor setpoint (stock sensors are all lambda=1 or in terms of gasoline 14.7:1).

 

Look at LSV2. You can see that it starts out at 250 mV and after about 15 data points it begins flipping from high to low voltage. Notice that the amplitude increases as the engine keeps running. Now look at LCF2. It varies between about 1.00 and 1.03. This means that the BMSK needed about 0% to 3% more fuel than the calculated-fuel-pulse to achieve 14.7:1.

 

Now look at LSV1 (right cylinder). As that sensor comes on-line, the voltage heads straight to about 300 mV. It means that the cylinder is running lean. Next look at LCF1. Between points 19 and 34 it ramps from about 1.00 to about 1.25. That means it took an addition of 25% to the calculated fuel pulse to get the Right Cylinder to reach 14.7:1.

 

The reasons for this that come quickly to mind are:

1) Too much air in the right cylinder due to: an air leak or a problem with the idle stepper motor.

2) Too little fuel: a clogged or bad injector.

3) Some problem that has caused the Long Term Trim for Cylinder 1 to become very lean. The Long Term Trim cannot be seen and it would take an oscilloscope to measure right pulse width versus left pulse width. A way to debug this type of problem is to use the GS-911 to clear all adaptive values and then take a new Cold Start Log and see what happens.

 

An odd thing that is happening is that as the engine warms up, LCF1 settles back down to the same value as LCF2. I don't know if that's due to warming of the engine or due to the Long Term Trim for Idle being bumped up, reducing the LCF.

 

This data doesn't tell us what the cause of the problem is but gives roundy some things to look at. In any case, 25% added fuel to the right cylinder is a lot!

 

It will be interesting to see if the Cold Start log behaves in the same way.

 

[mneblett]

Given that plot, I'd want to look at the injector spray pattern to see whether the right injector is partially fouled.

[roundy]

Really interesting reading, on my tablet right now in the garage so going to pop indoors and take it all in.

 

Here is the log I took tonight, cold start, but weirdly thus time I needed no additional throttle!?!

 

https://www.dropbox.com/s/9aoygkiihsq9a52/log%202015-03-24.csv?dl=0

 

With regards to the injectors, I had them serviced a few weeks back, were a little down on WOT flow, but otherwise very good for a 75k mile bike!

 

When I was watching the logs tonight from cold I thought the o2 sensor readings looked very weird....?

[dirtrider]

Afternoon Roundy

 

I just don't see any smoking gun in that cold start data.

 

But as you say, it started good so it probably wouldn't look

bad.

 

Maybe try to catch it & record data on a no-start without throttle condition.

 

I do see the fuel pump (shown) not running at key-on so I looked at the data from my (perfect starting 1200RT) & it shows the same (0) in the fuel pump at key on. (can you hear your fuel pump run for a couple of seconds at (first) key on?)

 

I also looked at my good starting good running 1200RT (old trapped data) & my lambda control factor 1 & 2 look almost the exact same as your first .csv so I don't think that is telling us anything.

 

About the only thing that I see different between my 1200RT cold start & your cold start data is your cranking battery voltage is notably lower at first cranking. (so if nothing else found try keeping your battery on charge overnight, or jump from another vehicle for first cold start to see if that makes a difference.

 

[roundy]

Trump card this morning, I started a log before I went off to work in hope, and she wouldn't start!

 

Here is the log: https://dl.dropboxusercontent.com/u/46259303/log2015-03-25.csv

 

I forgot to say I dumped some SeaFoam in the tank the other night, so perhaps that was why it started better, but maybe not! Had a generally nice ride into London this morning, just seems to be when she gets hotter the general running gets worse.

[roger 04 rt]

I took a look at the data this morning and don't see anything in it that will be useful for debugging the problem. The only significant difference I could see between the no-start condition with no throttle, and the did-start condition, was that you'd cracked open the throttle. Every sensor and the BMSK was doing its thing.

 

As DR mentioned, the battery voltage dips to about 9V for a moment but I don't have my other R1200 logs with me so can't compare.

 

I noticed the temperature is about 5 degrees C, which doesn't seem terribly cold.

 

Since the difference looks to be that you open the throttle and the engine gets a bit more air, are the throttle bores in need of cleaning or are the stepper motors sluggish and not adequately opening?

 

 

[dirtrider]

Morning Roundy

 

As Roger mentioned, no smoking gun on that data stream.

 

As noted some low voltage during cranking but it actually dropped lower on the second try where it started.

 

About the only thing I see is that you didn't pull the clutch in today (when it didn't start) & did pull the clutch in yesterday when it did cold start. But it isn't that cold so it shouldn't make that much difference.

 

As Roger mentioned it might be a basic (closed throttle air flow problem) but the stepper counts were the same today (no start) as they were yesterday at OK start so nothing positive on this one.

 

We might be chasing something that isn't trapped, like low initial fuel pressure (bad FPC, or low output fuel pump, or ??) or something like oil fouled lower spark plugs that clear up after start up, or a bad lower coil or coils.

 

Back to Roger's thoughts on coked throttle bores-- If you can trap us about 20 seconds of hot engine closed loop data (after a hot ride hook up GS-911 then run engine again for about 2 minutes (with a couple of throttle blips) THEN trap a little idle data. We can then compare the stepper counts to a known good 1200RT at hot idle. If your stepper counts are higher by much then you probably have restricted base idle air flow (like coked throttle bores)

 

 

[roger 04 rt]

Hi DR,

On a Hexhead, is there any way that the Idle steppers get sluggish enough that they don't open as much as commanded by the BMSK?

 

I ask because the BMSK knows the air and oil temperature so presumably it knows how much to open the idle motors for any temperature.

 

Also I noticed the 20 mS to 40 mS initial injection pulses. Quite a healthy shot of fuel.

[roundy]

Ok guys, some more logs, I hope I named them correctly but I think I may have confused myself!! :-D

 

https://dl.dropboxusercontent.com/u/46259303/after%201hr%20ride%20hot%20idle%20with%20blips.csv

 

https://dl.dropboxusercontent.com/u/46259303/after%201hr%20ride%20hot%20idle.csv

 

https://dl.dropboxusercontent.com/u/46259303/hot%20idle.csv

 

https://dl.dropboxusercontent.com/u/46259303/start%20hot%20and%20idle.csv

 

I didn't switch her off for the after logs, straight on the GS-911 when I got home, she sounded like a back of potatoes!

 

[dirtrider]

Hi DR,

On a Hexhead, is there any way that the Idle steppers get sluggish enough that they don't open as much as commanded by the BMSK?

 

I ask because the BMSK knows the air and oil temperature so presumably it knows how much to open the idle motors for any temperature.

 

Also I noticed the 20 mS to 40 mS initial injection pulses. Quite a healthy shot of fuel.

 

Afternoon Roger

 

Steppers are stepper motors so as a rule don't get sluggish, but being stepper in design they can get lost as the screw drive slips or jumps as the pintle position changes.

 

Steppers seldom cause problems on a cold start as they re-home at key-on then continue to move from there. Usually the stepper's biggest issue is getting lost after a long hi-way run with no idle time with stepper pintle continually following throttle position, OR, the other failure is simply quitting to operate.

 

I looked at the stepper cold start command & Roundy's matches a good starting bike so they appear to be commanded to the proper cold start position. A look at commanded stepper position after a nice long hot engine run should tell us IF the steppers are getting lost or not.

[dirtrider]

Ok guys, some more logs, I hope I named them correctly but I think I may have confused myself!! :-D

 

https://dl.dropboxusercontent.com/u/46259303/after%201hr%20ride%20hot%20idle%20with%20blips.csv

 

https://dl.dropboxusercontent.com/u/46259303/after%201hr%20ride%20hot%20idle.csv

 

https://dl.dropboxusercontent.com/u/46259303/hot%20idle.csv

 

https://dl.dropboxusercontent.com/u/46259303/start%20hot%20and%20idle.csv

 

I didn't switch her off for the after logs, straight on the GS-911 when I got home, she sounded like a back of potatoes!

 

Afternoon Roundy

 

OK, I took a quick look at the data (I will look closer, later, when I get a chance.

 

Your hot idle stepper position looks like it is quite a bit more open (higher counts) position than other 1200RT bikes that I have looked at. No way to tell if that is due to throttle bore coking or just a high mile engine (All the 1200 data I have with me here is taken at much lower miles. In any case it brings up a POSSIBLE throttle body coking problem as something to look at (or just clean them to eliminate that)

 

No chance you have tight valves is there?

 

The other thing that perks my interest is the EXACT SAME stepper count on both sides almost all the way through the data stream. I don't show that on any other proper starting good running warm engine 1200RT idling in closed loop. (again just something to try to understand)__ Almost like it isn't going into closed-loop stepper control. (Roger, any thoughts on this?)

[dirtrider]

Afternoon Roundy

 

One more question:

 

How did your bike start back in 4/2014? I have an old .csv file you sent me on your bike back on 4/2014.

 

It shows the same hot engine stepper count as you show now.

 

 

[roundy]

Fine, owned the bike 7 years and this only started in the last 3 months max

[dirtrider]

Fine, owned the bike 7 years and this only started in the last 3 months max

 

Evening Roundy

 

That is not good news as the current trapped data is pretty darn close to the data trap you sent me back on 4/2014 so it doesn't appear that your cold starting issue is something the BMS-K is tracking.

[roger 04 rt]

Ok guys, some more logs, I hope I named them correctly but I think I may have confused myself!! :-D

 

https://dl.dropboxusercontent.com/u/46259303/after%201hr%20ride%20hot%20idle%20with%20blips.csv

 

https://dl.dropboxusercontent.com/u/46259303/after%201hr%20ride%20hot%20idle.csv

 

https://dl.dropboxusercontent.com/u/46259303/hot%20idle.csv

 

https://dl.dropboxusercontent.com/u/46259303/start%20hot%20and%20idle.csv

 

I didn't switch her off for the after logs, straight on the GS-911 when I got home, she sounded like a back of potatoes!

 

Afternoon Roundy

 

OK, I took a quick look at the data (I will look closer, later, when I get a chance.

 

Your hot idle stepper position looks like it is quite a bit more open (higher counts) position than other 1200RT bikes that I have looked at. No way to tell if that is due to throttle bore coking or just a high mile engine (All the 1200 data I have with me here is taken at much lower miles. In any case it brings up a POSSIBLE throttle body coking problem as something to look at (or just clean them to eliminate that)

 

No chance you have tight valves is there?

 

The other thing that perks my interest is the EXACT SAME stepper count on both sides almost all the way through the data stream. I don't show that on any other proper starting good running warm engine 1200RT idling in closed loop. (again just something to try to understand)__ Almost like it isn't going into closed-loop stepper control. (Roger, any thoughts on this?)

 

Good Morning DR,

Although I don't have my base of R1200 GS-911 data with me, from memory the counts are often the same. Where they diverge significantly is when the tank vent opens. Then the BMSK closes that stepper motor by a set amount.

 

We know the BMSK can independently get afr equal using the lambda sensor. Do you know if the BMSK can also get the idle air equal by measuring the rotation speed of the engine?

 

Even the older Motronic knows when rpm isn't stable (by measuring rotation speed) after starting and makes a spark timing adjustment if the engine isn't running smoothly. So it's conceivable that the BMSK could measure rotation by rotation rpm and make side-to-side idle air adjustment if needed.

[dirtrider]

Morning Roger

 

Unlike the old slow response 2 position reading HES of the 1100,1150 era the 1200 uses a modern type inductive sensor that reads off of the upper balance shaft drive gear so it's possible the BMS-K can get a RPM variation reading (but I would be very surprised if it actually does that).

 

On the early (independent cylinder head) input temp 1200's some (or most of) the idle air balance was done using the cyl head temp input & o2 input as fooling with either would effect the stepper position & balance.

 

On the later 1200RT's like my 09, BMW went to only one cylinder head temp input & split that for both side inputs. I'm not exactly sure how they control stepper balance on the later (single head temp) 1200's but my 09 1200 has the single cyl temp input (so both sides always read the same) & very seldom do the steppers match side to side at hot curb idle once it enters closed loop.

 

If I disconnect the o2 sensors the system goes open loop & then the steppers link up to be the same side to side as well as always lining up to be the same side to side as the throttle is opened, even in closed loop.

 

The other thing the later (not sure went it went into production) 1200's have is a system voltage idle RPM kicker that raises the engine hot curb idle RPM if it senses lowering system voltage. On this I'm not exactly sure IF the BMS-K allows independent stepper control or links the steps to be the same side to side.

[roger 04 rt]

Morning Roger

 

Unlike the old slow response 2 position reading HES of the 1100,1150 era the 1200 uses a modern type inductive sensor that reads off of the upper balance shaft drive gear so it's possible the BMS-K can get a RPM variation reading (but I would be very surprised if it actually does that).

 

On the early (independent cylinder head) input temp 1200's some (or most of) the idle air balance was done using the cyl head temp input & o2 input as fooling with either would effect the stepper position & balance.

 

On the later 1200RT's like my 09, BMW went to only one cylinder head temp input & split that for both side inputs. I'm not exactly sure how they control stepper balance on the later (single head temp) 1200's but my 09 1200 has the single cyl temp input (so both sides always read the same) & very seldom do the steppers match side to side at hot curb idle once it enters closed loop.

 

If I disconnect the o2 sensors the system goes open loop & then the steppers link up to be the same side to side as well as always lining up to be the same side to side as the throttle is opened, even in closed loop.

 

The other thing the later (not sure went it went into production) 1200's have is a system voltage idle RPM kicker that raises the engine hot curb idle RPM if it senses lowering system voltage. On this I'm not exactly sure IF the BMS-K allows independent stepper control or links the steps to be the same side to side.

 

Interesting about the use of cylinder head temperature for idle balance.

 

The BMSK "could" use a slow average of the cycle by cycle rotation speed to change idle air but it is only speculation on my part to suggest that it does.

 

Back to roundy's issue, your suggestion that he connect a jumper cable to a car battery would be my next check.

[roundy]

Wow, its incredible reading your guys diagnostics and posts!!

 

I think the first step for me is to take the TBs off this weekend and give them a good clean - anything in particular I should pay attentions to?

 

Valves should be good, serviced last weekend and checked all that.

[dirtrider]

Afternoon Roundy

 

I think I would try a battery jump on cold starting first.

 

On the TB cleaning___

 

Probably no need to remove the TB's as about all you need to look at, or clean is the throttle bores around the throttle plate area. You can do that in place with cat converter/o2 safe carb cleaner. Put a drain hose on each TB bottom nipple to allow safe drain off away from painted surfaces on the bike.

 

Also look at the rubber boots between the TB's & the cyl heads for signs of cracking or air leaks.

 

If you do remove the TB's then look at the back of the intake valves for signs of heavy coking on the back side of the valve head.

 

If cleaning the TB's off the bike be very careful of the TPS sensor so you don't get any cleaner in or on TPS sensor.

 

Also be careful to NOT move any of the base idle stop screws as those are about impossible to return to proper position.

 

If you remove either stepper NEVER turn the key on with a stepper plugged in or it will screw itself all the way out & those are VERY difficult to get re-assembled again.

 

[roundy]

OK, will give all that a whirl.

 

Interesting about the battery, was a new one about 2 months ago.

 

So, just remove the air intake side boot and clean from that side??

[Boffin]

 

Interesting about the battery, was a new one about 2 months ago.

 

 

How clean are the terminals? The internal resistance of batteries increase with lower temperatures, add that to a slightly dirty terminal and you could well reduce the available starting voltage.

 

[greiffster]

Fine, owned the bike 7 years and this only started in the last 3 months max

 

Interesting about the battery, was a new one about 2 months ago.

 

Smoking gun?

[roundy]

I replaced the battery about 6 months ago, but the first unit was duff, had it replaced with a replacement unit.

 

I'll check out the battery on my tester tomorrow and check the connections. Where does the positive and negative cables go to, so I can check that end - assume positive to the alternator?

 

Interesting thing tonight though, when I pulled into the drive the bike was lumpy as hell, like handle bars rocking (

)

 

Switched the bike off, waited and re-started (no additional throttle needed) and the bike idle was much smoother - just thinking in regards to steppers going squiff and then re-setting.

[dirtrider]

 

Switched the bike off, waited and re-started (no additional throttle needed) and the bike idle was much smoother - just thinking in regards to steppers going squiff and then re-setting.

 

Afternoon Roundy

 

Possible, the only way that you would know that is to either try new steppers_ OR, grab a .csv file after riding home BUT WITHOUT turning the engine off. Once you key-down & restart, the steppers will reset, so your GS-911 will only catch the stepper counts being askew IF the engine remains running after the long ride.

[roundy]

Ah,the "after ride" log from yesterday was done without switch off

[dirtrider]

Ah,the "after ride" log from yesterday was done without switch off

 

I took another look at that .csv & unfortunately can't tell you much.

 

What I usually see with a stepper that gets lost is a post ride discrepancy on the counts as the BMS-K keeps adding (commanded) counts on one side to bring the idle RPM up to desired.

 

With your (commanded) stepper counts staying the same side to side I'm not sure what we are working with. Maybe the stepper counts locked even on both sides is telling us something but at this time I just don't know what it is telling us.

 

One thing you might do is add a couple of vacuum hoses to the TB nipples then run them up under the seat & plug them off.

 

Then after the ride home, & without turning the engine off, clamp off both side hoses (to prevent vacuum leaks) then unplug the hose caps & hook up your U tube manometer, then unclamp the hoses.

 

If your GS-911 shows even stepper counts side to side AND you show somewhat even idle vacuum side to side then the steppers are working OK.

 

On the other hand IF your GS-911 shows even stepper counts BUT the side to side vacuum is way off then you know one of your steppers isn't where the computer has commanded it & is basically lost.