Rough tickover and popping on a closed throttle

Bones · Mar 24, 2017

After a blast up the motorway I hit the London traffic to find the old girl running a bit rough. She is fine under load and with a few revs but low speed and sitting at lights at tickover is very lumpy. She is also popping away when closing the throttle when slowing. What do reckon? One of the plugs failing? Lambda sensor? Fuelling? Hopefully she will get me home, it beer night

comberjohn · Mar 24, 2017

If it only started after a blast up the motorway, I would hazard a guess at coils?
Never had it myself but have read that earlier models had a habit of overheating them and breaking down.
Bendy will be along shortly.

Bones · Mar 24, 2017

I wondered about coils (causing one of the plugs to not spark) as to my knowledge none have ever been replaced and I've had the bike 11 years/67K miles. Presumably the bike will still run with just one plug sparking on one pot. As long as I can clear the London traffic without a breakdown this evening I think it will be fine once I get on the faster roads, although I won't give it the usual caning.

Khulu · Mar 24, 2017

Coils can break down with heat - it's happened to me before on different bikes.

oldnfat · Mar 24, 2017

I have had a similar situation with plugs breaking down. I would go for those first as cheaper than the coils. Having said that I you are on the original coils you have done well and that is where I would go next.

Good luck.

Bendy toy · Mar 24, 2017

comberjohn said:
Bendy will be along shortly.

Popping on overrun suggests over fueling so it could well be coil or coils. If you have the black painted type they have to be top of the list.
It's not like an Alfa TS engine. The secondary coils spark a good deal later than primaries so engine will run tough when a primary fails.

Sent somehow.

Bones · Mar 24, 2017

Thank you all. Coil(s) seem the likely cause here then

tuftywhite · Mar 24, 2017

I'm going for secondary coils which are only used at low revs.

When mine started to go, it was rough at low revs, but made excellent popping noises on the over run.

unibar · Mar 24, 2017

I had similar.. Pop a meter across the pins on the throttle position sensor, set to ohms.. There should be no open loop.. Takes all of 2 mins

Sent from my SM-G920F using Tapatalk

harry · Mar 24, 2017

I'm going for TPS

Bendy toy · Mar 24, 2017

If it's the secondary coils simply unplugging the connectors should prove it.
However mine make no difference on or off that I can detect. Yet their plugs are always the correct colour suggesting they do still work.
Failing black painted coils will smell burnt.

Bones · Mar 25, 2017

Confused now. Started the bike for my 40 mile ride home after checking that I had the breakdown recovery number stored on my phone. Bike was perfect on startup, 'ahah' I thought, coils break down when hot. Rode home, bike was fine even after the motorway blast, although I did restrict my speed to 90 rather than the three figure speed I 'might' have accidentallyattained on the morning ride.

GS's really are miracle bikes, I had an ABS /speedo fault that fixed itself when the frosty weather stopped, and now a coil has self repaired. I have a replacement ABS sensor ready to go on. I fully expect both to play up again. New coils aren't cheap though, I did consider replacing all 4 because of their age but you are looking at around £400 for the set.

Bones · Mar 25, 2017

harry said:
I'm going for TPS

I did try the reset procedure when I parked up in the morning. The bike was fine in the evening so I do hope that you are correct

tuftywhite · Mar 25, 2017

Bones said:
New coils aren't cheap though, I did consider replacing all 4 because of their age but you are looking at around £400 for the set.

I bit the bullet and did all four of mine. It's now smoother than a smooth thing.

Edit: I did buy them at Motobins 20% off day. Could be worth waiting for, although I can't remember when it is.

Bendy toy · Mar 25, 2017

If you have the old black coils smelling burnt, you only need to replace the primary coils.
Run the bike for a while before checking the secondary plugs. If the tip colour is good the coils are working so no need to replace.
They run in air so assuming no corrosion they should last indefinitely.
Speedo sensors fail but more check out the connector before scrapping what may be a good sensor.

NZRalphy · Mar 27, 2017

Unplug and remove both O2 sensors. Light greys is good black n sooty is bad. If it is sooty then you may have a bad O2 sensor..... and the bike can adapt around this. It's worth a check.

Pukmeister · Mar 28, 2017

Closely inspect ALL your spark plugs for erosion of the centre electrode on its flanks, they wear oval pretty fast. If the plug gap gets around 1mm the engines get rough and the coils strain to produce a fat spark. Either bend the earth electrodes in to narrow the gap to 0.7mm a side, or fit new plugs.

20 minutes spent on the basics........

Rough tickover and popping on a closed throttle

Bones

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comberjohn

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Bones

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Khulu

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oldnfat

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Bendy toy

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Bones

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tuftywhite

getting away with it so far!

unibar

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harry

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Bendy toy

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Bones

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Bones

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tuftywhite

getting away with it so far!

Bendy toy

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NZRalphy

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Pukmeister

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