Throttle body sticking on R400

[Steve Campbell]

Hi folks. Strange problem today at track day. This is a 2008 R400 standard set up.

The throttle body is sticking around the idle point, resulting in the car revving at between 3k and 4.5k when idling. Stripped it down and tried to clean with WD40 (that's all I had). It's definitely the body and not the cable as it was sticking with the cable disconnected. Didn't help. It seems to come on when the engine is hot, but not when cold. Bizarre as the car was fine first thing, and this developed during the day. Feels like the butterfly valve is catching ..... but couldn't really see any deposits after I cleaned.

We tried all sorts but no luck. Will clean it properly now I'm home but anyone experienced this and got any pointers to look for ?
Thanks

[downsman]

I don't have an R400, but I have heard of some Caterhams where the throttle body can distort if the jubilee clip attaching the air filter is over tightened.

[allen l]

In my case WD40 did the trick.

[Steve Campbell]

Thanks for the thoughts so far. The overtightened clip idea was one we played around with....but it still did it when hot when the clip was only just nipped enough to just hold the air filter on !

Keep the ideas coming :-)

[DCL]

Any big back-fires? Could be that the spindle or butterfly have become damaged (bent). But it could just be that it's not aging well and has distorted it a bit.

[Some Gump]

Mad an R300 butterfly stick open due to the plastic bush bit wearing and jamming open. Are there plastic bits on the r400 bodies? If so, similar thing could happen I suspect.

[anotherjohnv]

mine stick because the engine spat a bit of valve through it. But I suspect that's not your problem

[Steve Campbell]

Ok think it's fixed :-). Having given it a proper clean with carb cleaner, the butterfly valve was 'just' catching at the bottom. On closer inspection, it looks like the valve was ever so slightly misaligned....so I undid (<1/2 a turn) one of the torx screws holding it to the centre arm, realigned, then tightened it all up. Seems to be ok but have not taken it for a full hot run yet .....but it does look ok.

Phew...thought I was going to have to buy another at ~ £350 !