Random Idle balance; Erratic Idle & rough running

[Austin]

OK two things, probably the same cause though.

2011 GSA 83,000 miles. Valves in tolerance (just) last time I checked.

1. Random throttle balance

See this video filmed today after fiddling about with throttle cables and connectors to TPSs, Idle Valves, & Injectors in an attempt to find a cause for fault 2. At around 10 seconds, 33 seconds and 55 seconds the balance goes off the scale with no input from me other than holding the throttle above tickover (the gradual rising and falling of engine speed and associated gradual changes in balance are me - the sudden and extreme changes in balance are random and unexplained). I am using GS911 so the idle stepper motors are parked. Any thoughts? I did eventually get the balance to be around zero at 3,000ish rpm.

 [youtube]OK two things, probably the same cause though.

2011 GSA 83,000 miles. Valves in tolerance (just) last time I checked.

1. Random throttle balance

See this video filmed today after fiddling about with throttle cables and connectors to TPSs, Idle Valves, & Injectors in an attempt to find a cause for fault 2. At around 10 seconds, 33 seconds and 55 seconds the balance goes off the scale with no input from me other than holding the throttle above tickover (the gradual rising and falling of engine speed and associated gradual changes in balance are me - the sudden and extreme changes in balance are random and unexplained). I am using GS911 so the idle stepper motors are parked. Any thoughts? I did eventually get the balance to be around zero at 3,000ish rpm.

 [youtube]https://youtu.be/iOFkHllXLmY[/youtube]

2. Before I did this I have been suffering for some months of an intermittent and random poor tickover and roughness. Both come and go randomly together but never seem to last too long. I have had the GS911 on when it was doing the poor tickover thing and nothing seemed to have changed in real time values from when it was running OK. The poor tickover is either an erratic tickover pulsing of around 1200 - 1500 rpm, or a complete unwillingness to tickover. It feels and sounds like the engine is waaaay out of balance when it does this - hence my though that 1 & 2 are linked. In both cases of erratic tickover and roughness if I just weight the throttle the tiniest bit it runs ok(ish) and somewhat smoother - but revs are up to about 1500rpm. When its doing this if I ride it then it feels out of balance, and quite rough - lumpy rather than buzzy. Switching ignition off/on has cleared it but most times not.

The symptoms have NOT appeared on a proper cold engine, and most commonly occur after a long closed throttle slow down or when hot like in traffic.

Over the past couple of months I have had the following faults: Left Hand Lambda Sensor value out of range. New sensor fitted - no change. I also got hold of a used set of 4 stick coils. No change, I am back on the originals now. I had a knock sensor fault the other day - value too high, but that could be caused by anything. I have reset adaptations and done idle valve calibration umpteen times. Nothing simple like this seems to cure it.

Real time values on the GS911 all seem to be OK, specifically the lambda values are (now) both in range and jump about as they are supposed to. Other values that are also paired all seem to rise and fall together except for the Knock sensors which have a significant difference. Not sure if that is normal not or what a typical value should be.
Edit.....the additive Trim adaptation values also seem to differ quite a bit for each cylinder, but not sure what the scale is. -3.19% one side -3.98% the other. (an adaptation reset puts these back to zero and the ECU then learns what adaptation to apply).

Any ideas anyone.

Oh, and the flat spot between about 5,000 and 6,000 rpm seems to gone bigger than ever.[/youtube]

[Jughead]

Hi Austin

It would appear that you have covered virtually all the bases here, and this does narrow things down somewhat.

What immediately comes to mind is stick coils.  You have replaced all 4 so that does kind of eliminate them.  However, you need to check the actual stick coil connector/plug at the end of the harness.  These have a tendency to break internally.  There is a repair kit available from BMW.  (Part Number: 83 30 0 402 341)



Firstly, try the following:

Unplug the upper stick coils altogether and start the motor.  The motor should run fine and smoothly at idle.  Play around with the stick coil connectors and see whether the motor falters at all.  As you bring the revs up, the motor will die at around 3000rpm, as this is when the lower plugs stop firing.

If all is well, reconnect the upper coils and unplug the lower ones.  Start the motor again and play around with the wiring to the upper coils.  If the motor misfires at all while moving the harnesses, you may have located the problem.

If all is well with the plugs/harnesses, maybe try replacing the TPS.  They do at times go faulty without any error being recorded.

[Austin]

Thanks I will try the coil connector thing shortly. 

I have also posted this query on UKGSer where the TPS has also been suggested.  Is replacing the TPS plug and play?  My Haynes workshop manual suggests not, or is it just saying that an adaptations reset and throttle balance needs to be done after replacement. 

After posting my original post I went back to try out the bike, whilst it started and ran ok after about 400yards I had to slow to an almost stop and the bike would not run below about 1800rpm - revs just fell away completely and it died.  It took a big handful of throttle to get it going again.   With a bit more throttle it ran ok and I went a mile or so up the road but it felt lumpy and wrong and stayed that way until i got home again always having to keep the revs up to stop it dying. 

This morning it didn't want to run much at all for the first couple of presses of the starter but then suddenly cleared and I let it tickover until warm.  Blips of the throttle get a normal response.  I took a couple of CSVs from the GS911. 


CSV One is about 5 minutes of arm up.  Mostly at tickover but with a few throttle blips and steady throttle above tickover.

CSV two was an attempt to hold a steady throttle just off tickover.  The read shows a steady 1.18 for the throttle position (column L) with some intermittent drops to 0.78 whereas I held the throttle steady throughout except at the end.  Is this a sign the TPS is failing. 

[Jughead]

Thanks I will try the coil connector thing shortly. 

I have also posted this query on UKGSer where the TPS has also been suggested.  Is replacing the TPS plug and play?  My Haynes workshop manual suggests not, or is it just saying that an adaptations reset and throttle balance needs to be done after replacement. 

TPS replacement is straight froward plug and play, followed by an "Adaption Reset"

The symptoms you describe could very well be TPS failure.  In essence, the system doesn't know how to control the fueling since it cannot determine where the throttle position is.  It may be a good idea to just get a loan one from another bike to see whether it resolves the issue.  TPS can be rather pricey.

[Austin]

Someone on UKGSer did a good job identifying alternative parts.  £38.50 for this one https://www.ebay.co.uk/itm/172741967895?clk_rvr_id=1517610080367&rmvSB=true

Part number is 6PX008476-111

I think at £38.50 I will give it a go.

Here's the UKGSer thread  http://www.ukgser.com/forums/showthread.php/478103-Throttle-position-sensor-alternative-part

[Austin]

just did the check on the Coil sticks.  No amount of wiggling of any of the connectors made any difference.  They also look to be in great condition anyway. 

[Jughead]

Hi Austin

You ever resolve this issue?

[Austin]

Hi Austin

You ever resolve this issue?

Yes, I should have updated the thread.  A new Throttle Position Sensor seems to have sorted it.    Very easy to fit and with a throttle body balance the bike was transformed.    I began to suspect it was the TPS after closely watching the readout for the TPS on the GS911, there was just a little flutter in the readout every now and then at tickover and despite holding the throttle absolutely rock steady at just off idle I was also getting small fluctuations in the readout.   Water ingress probably.  I know they can be cleaned/repaired with care but I got a Hella TPS for a BMW car.  There's a link on UKGSer somewhere to an Ebay seller.  £25 instead of £125.  It was worth a try at that price anyway.  Identical part. 

[Jughead]

[emoji106]

Awesome.  Pleased you got sorted.

I purchased an accident damaged bike on auction about 2 weeks ago.  Had a very similar problem where the motor was very rough and sounded like it was only running on one cylinder, although both headers pipes were the same temperature.  Turned out to be the idle bypass valve that was faulty.

Have subsequently had a client's bike in with similar symptoms, also with a faulty bypass valve.