Throttle sticks open

[Yatz]

I had a "fun" incident with my Chimaera 450 today. I accelerated quite vigorously and the throttle stuck open. I turned off the ignition, pulled over, started the thing again and all was fine. As an experiment I did the same thing on the next straight bit of road and it happened again. Now, I drove about 10 miles to my home and all was well when driving gently, the problem only seemed to emerge when the throttle was depressed to over half way. I am assuming, therefore, that this is merely a lubrication issue (though the cable might need changing) and nothing electrical. Anyone else out there had this? I shan't be able to take it to a garage till after the yuletide ritual is over but it might be something I could fix "roadside" with a drop of oil.

[sixor8]

Check the throttle return springs are still attached under the bonnet. There should be two but many cars (including a past one of mine) only had one, possibly deliberately to make it less stiff. If this breaks or comes away, the throttle plate is liable to stick open.

[Pagey430]

Also maybe check carpet in the footwell by the throttle pedal arm as any movement in the carpet can easily prevent return of the arm

[Belle427]

Get someone to operate it through its range while you watch the mech under the bonnet, check the cable itself has not been trapped or run somewhere it shouldnt be.

[Bowks]

Pagey430 said:

Also maybe check carpet in the footwell by the throttle pedal arm as any movement in the carpet can easily prevent return of the arm

This. I had mine stick open on the raised section of the M5. The most terrifying thing I've experienced in a car as I didn't work out it was the carpet until I finally came to a rest.

[Classic Chim]

It happened to me in an E Type Jag with a very expensive light weight racing bonnet, very disturbing.
Always check carpet first as it often only shows itself with a good old flat out blast.
While your down in the footwell checking use a torch to look for bent/fraying throttle cable or restriction of throttle pedal.
Then move onto engine bay etc.
Some people remove one throttle spring to make pedal feel lighter. I replaced one spring for a lighter one but I’d never run with just one spring.
I’d expect it to be carpet/ rusty/ fraying cable or indeed trapped bent section of cable as the main suspects.

[Classic Chim]

Remove throttle springs in engine bay and see how free the cable operates.

[Yatz]

Thanks for the feedback, everyone. One aspect I am yet unsure about is whether the pedal itself was not coming back or whether the pedal was returning but the engine was still revving. As I am sure you can all imagine, the occurrence was a tad alarming and although I did deliberately make it happen again, I couldn't keep doing so as the road had too few straight sections and it was wet as hell. As a result I couldn't keep triggering the problem to see exactly what was going on. My worry is that the cable has become frayed and so a mere lubrication job won't be enough. However, the fact that I hadn't driven the car in six days and that the weather is so cold and damp (I don't have a garage) makes me think that the cable is merely sticking a bit. Once the turkey and stuffing ritual is out of the way I can have it properly looked at.

[cliffords]

I had a car where full throttle over extended the butterflies and so they stuck.
I had to adjust the cable to only go to the stop

[Belle427]

Can be beneficial to replace the cable as part of the maintenance.

[s p a c e m a n]

I had a stuck cable at the start of the year after it had been sitting for a few months, had to pull the pedal back up with my foot it was so stuck.

Was bit of a pig getting access to fit one of these...

https://www.ebay.co.uk/itm/155134716883?mkcid=16&a...

at the throttle body end but I managed to get half a can of plus gas down the cable and it worked perfectly again until the cable snapped a month ago