2005 Sprint 1050 ST - occasional low idle speed

[SteveSmith]

My Sprint usually idles at around 1000-1100 rpm (1500-1600 when cold), which is fine. it's not the smoothest idle I've ever heard, but for a triple it certainly isn't rough or lumpy.

In the last few weeks though, especially when dropping off the throttle too quickly, the revs occasionally seem to drop through the normal idle speed and try to idle at 700-800. At that point it either struggles or stops entirely but it won't pick back up to 1000 without a bit of throttle.

It's due a major service, which I'll do in the next few weeks. Does this sound like something that valve clearances and throttle balancing will fix, or could it be the first sign of something else going wrong?

Thanks,

Steve.

[jaffa90]

It's possibly a partially stuck idle stepper motor linkage, the linkage is between the stepper motor and the throttle body butterflies and can become a little ‘sticky’ over time, especially in the winter.
When this happens the stepper motor cannot open throttle valves enough for a fast idle and this will cause a poor idle when cold. You will need to remove the airbox, then spray some lube on the linkage to free it up.
It's a good idea to have it done at a dealership as they will be able to adjust the linkage if necessary, which is done using the Triumph Diagnostic Tool.
Another possibility is a faulty or misadjusted TPS, the only way to test this is again at a dealership with the diagnostic tool.
FOUND THIS ON ANOTHER FORUM.

[Meatybeaty]

Sound advice Jaffa

[SteveSmith]

[SteveSmith]

I'm just resurrecting this a year on in case anyone searches it with the same problem. Unfortunately lubing the linkage was only a temporary fix, the problem carried on and got gradually worse to the point where it would stall every time I let go of the throttle.

It was checked out with genuine triumph diagnostic kit and everything seemed to be working perfectly. There were no fault codes and the stepper motor and TPS were both bang on spec. I replaced the stepper motor and speed sensor (which is apparently involved in idle control) with brand new genuine triumph parts but the problem persisted.

Eventually last night I took off the complete throttle body and replaced it with one bought from a breaker for £35, and it has completely solved the problem. I wish I'd done that a year ago, but hindsight is a wonderful thing!

This has been a massively frustrating fault and I almost reached the point of selling the bike and starting again. On the plus side I've learned a lot in the process and now it's like having a brand new bike again.

I hope this is useful to someone else at some point.

[Evil Hans]

Always nice to get a final update like this - on behalf of everyone searching for a fix in the future, I thank you!
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Triumph Sprint ST 1050. And it's Red.