Engine Revs When Braking??????

Here’s an odd one.
I thought first time it happened I was touching accelerator pedal at same time as brake pedal but I watched what my feet were doing and not the case!!
When I take my foot off the accelerator pedal and brake the engine sometimes revs to about 3000rpm then drops back to normal tick-over.
Before I send it off to the expensive Lotus garage - any ideas?
(I guess Mark will say TPS )

I had a encountered a similar problem to yours which was caused by the throttle bodies starting to stick .

These were later replaced when they stuck completely .

I was also told that this might have been caused because my car was over fuelling , caused by a faulty map sensor .( look out for black smoke if it is )

Or try an emmisions test ???

I’ll have throttle bodies checked - but I can’t believe it is that cos car revs when I brake - sounds more like something is moving, that affects engine revs, with braking force - I can even blip the throttle by pumping brakes - really strange. Maybe if I put padgids in car would be faster??
Checked car at a stand still, it does not rev engine when I pump brakes then - so not linked to electrics/brake lights.

They solved my problems which were similar to yours .

I also remember having excessive black smoke when thrashing the car , when I was going through the gears on trackdays .

Also my emissions reading was 18 when a Mot pass is 5 ( I think ).

That was without the Cat though .

Hope you get it sorted whatever it is for the least expense .

Good luck

Thanks Graham.

If the throttle bodies are beginning to stick you need to get them sorted before they stick wide open - it is fun, but obviously can be dangerous!!

If they are sticking a bit open and you brake, the revs will come down, cos the brakes are stronger than the engine, but if you then dip the clutch you would get a sudden rise in revs…

Could this be what was happening?

(I guess Mark will say TPS )

TPS! TPS! TPS!!! Well just doing whats asked of me

Don’t think it is the TPS tho’, as folks say, TB’s sticking… Unless the throttle cable is too toight (yes toight, loike a toiger!) and is somehow affected by the brake pedel?

Bushes in the pedal linkage ?

Mike - engine only revs whilst I’m braking - if I press clutch revs drop to 1250rpm - like they should.
It’s only when I brake that the engine revs - and if I pump the brakes it blips the throttle!!!
Phil - I think you win the Blue Peter badge - I’m going to play with a bush!! I could be some time!!

Bushes in the pedal linkage ?

Found some leaves - but no bushes!!

Naa - it’s not that!

It’s going to have to wait until Friday afternoon now - I will take air box off and have a look at throttles - I guess that if I take off air box I will be able to see throttle damper is sticking??
Where are bolts for air box??

There are 4 bolts holding the air box, 2 at the top and 2 below, you need a very small rachet with a 8 mm socket.

However if by pressing the brake pedal the throttle cable moves the problem is definately at the pedal box end, maybe the bolts that hold the pedal box to the chassis, these have been know to come loose and are a ba*tard to re-tighten !

Thanks Phil.
I’m convinced it’s at the rear - cos by pumping brake pedal whilst stationary I can’t get engine to rev.


what about loose engine mount causing engine to rock under braking and so pulling on throttle cable??

Try one thing before attempting other complicated stuff:

Spray a lot of WD40 on the return spring in the middle of the TB’s.
The same happened to me after a good engine wash, did the WD40 thing and presto!

Thanks chaps
There are a few things to try there!