Sticking throttle during gear changes......

[Eccles]

Dear POBC, Please help!

I have a problem with my throttle bodies causing the revs to sometimes hang during gear changes, the revs will hold high for a few seconds then return to idle. It doesn't always hang around the same RPM but seems to be related to how wide the throttle was open before and only happens when the engine is good and hot.

The car is a Sigma 150 so has the Caterham throttle bodies on it. I have tried replacing the throttle cable, have balanced and rebalanced the bodies just in case there was something weird going on there, but have since seen that when I get it to do it while parked I can see the throttle doesn't return to its stop (also seen on Easymap), but this is only when the engine is running, I've never seen the throttle stay open with the engine off.

I have also taken them off, given them a good clean, baked them in the oven for 1hr at 150c (shhh, don't tell the other half) to see if I can reproduce any tightness but it remains as free as anything.
There are no tell-tale scuff marks down the bores if the butterflies were catching because of too much endfloat.

Tried a new lambda sensor because I had one and it was a straw I hadn't grabbed yet.

Both return springs are there and as strong as I ever remember them.

Before I order a new set of bearings for the throttle spindles is there anything else I should be checking?? Any other ideas what could be going on??

 

TIA

Ivan
 

[SM25T]

Pivot at top of pedal can stick/bind. Loosen bolt and lubricate it. Refasten as required but check when finished.

[Tom_Arundel]

No tight bends/curves in the cable line

[Eccles]

Thanks both, will have a look at the pedal end and see if there could be a problem there. Hopefully the cable routing is OK as I have tried it a couple of ways since changing it.