Flat spot/Hesitation - Update

[Mac77]

hi all, my 2007 has developed a flat spot/hesitation under hard acceleration. I use UK super unleaded (BP & Shell). To give some history, my cruise control wasn't working since purchase 8 months ago and only recently, rectified it (microswitch issue). Since I've been using the cruise control, this issue has developed.


In any gear, if I grab a fist full, it just doesn't want to go. It will accelerate, but with no 'guts', then pick up and take off. On my way to work, the on slip to the A3 is very short and to get up to speed is getting a bit dodgy now as I just don't know what she's going to do.


I replaced the fuel pump control relay this morning (they collect some crap down there!) thinking it was a fuel delivery issue, but it's not rectified the issue.


I'm getting no error messages or signs. Will a dodgy TPS cause this or is it a potential coil issue?

[T6pilot]

My buddies 07 had same issue turned out as a bad coil

[Sullivj]

Mine was a fault with where the wiring meets the stick coil.

[Mac77]

Thanks guys. Will have a look at testing which one has failed.

[Casbar]

We had the same on one of our RTPs in the end it was feeling controlled by the ECU. Had to buy a new ECU, so really hope that is not your issue ££££££

[Mac77]

I hope not casbar! After doing some more reading today, it looks like it's one of the stick coils, so going to order some and try that. The general consensus is they're only good for 40k miles...

[David.]

Ignition stick coils do seem to have caused problems for some owners, what diagnostic methods were used to determine the fault.

[Sullivj]

I don't actually know what the mechanic did to resolve mine, but I do know what a MASSIVE difference it's made.


It ran like a tractor before, but feels like it could pull a wheelie now as it has so much power by comparison!

[futterweasel]

I hope not casbar! After doing some more reading today, it looks like it's one of the stick coils, so going to order some and try that. The general consensus is they're only good for 40k miles...


if thats the case 40.000 and your bikes fuc!ed thanks BMW wheres the longevity

[johnarthur]

Hi Sullivj, can you please find out what your mechanic did so that we can all benefit? 

[Mac77]

David, none yet. I put new plugs in only a thousand miles ago, so the coils are the last thing to check. I'll replace them next week and let you know how it goes.

[David.]

Have seen a couple of videos & posts on other forums where, whilst the bike is running at idle, the LT lead on each coil stick is disconnected in turn.

The theory seems to be, if disconnecting the LT lead/coil doesn't make any difference to the running of the bike, that particular coil is suspect.

Has anyone else heard of or used this diagnostic technique?

2004 BMW R1150GS Ignition Stick Coils, https://www.youtube.com/watch?v=hMJWr_BdNO8

[Mac77]

I saw ones like this, but my issue is when under quick acceleration. So after some reading, this technique can give you a false reading as you get a good spark at idle, but the coil fails when under load. I'll replace them anyway, peace of mind.

[David.]

A more scientific approach might be to use an adjustable spark gap tester,
https://www.machinemart.co.uk/p/laser-5 ... rk-tester/



Or, check the coil primary & secondary resistances with a multimeter.

[T6pilot]

Have seen a couple of videos & posts on other forums where, whilst the bike is running at idle, the LT lead on each coil stick is disconnected in turn.

The theory seems to be, if disconnecting the LT lead/coil doesn't make any difference to the running of the bike, that particular coil is suspect.

Has anyone else heard of or used this diagnostic technique?

2004 BMW R1150GS Ignition Stick Coils, https://www.youtube.com/watch?v=hMJWr_BdNO8




That’s what we did with my buddies bike, replacing left coil solved the issue