When I brake, my engine revs increase

[juk]

Has any one had this ?...seems like a brake servo problem, when braking for traffic lights etc, engine revs build up to between 2 and 3k with clutch pedal depressed. Diagnostics say all is OK

[BigOL]

As a long shot it could be your throttle butterfly rod (can't remember its techinical name) It sits in your intake manifold and controls the butterfly for idleing, it is located just beyond the map sensor and its a rod that basically when you take your foot of the throttle pedal which controls the butterfly (fuel / air mix valve into the engine) from closing completely which would make the car stall. Its controlled by a motor to help with the cold start routine and has a habit of getting gunk and stuff on it and might just need cleaning to help with a smoother operation.

This is especially the case if you use a K&N panel filter as the oil from the filter gunks up the MAP sensor and this part.

Do you rev's slowly die back down?? Or do they remain constant 2-3k.

If you want some DIY instructions on how to clean it, find the Clean Your MAP sensor thread in How to, as you need to remove this part to clean the MAP sensor, Sale (the poster) also includes a good description of what this part does as my explaination is a bit....erm...., vauge really.

Hope this helps

[Qwakrz]

Ok, try this.

Sit with the engine idle on the drive way, let the tickover stabalise & then press the throttle. If the revs increase it sounds like a leaking servo.

Stop the engine, let it sit for a while & then try the brakes. You should still get servo assistance for at least two presses (slightly less on 2nd press), if not then it is def the servo that has gone.

If you have an air leak into the manifold then it is possible that the ECU is adjusting the fuel to compensate and this is what is raising the idle.

[juk]

Cheers, I'll give it a go this weekend. I took the air filter out about an hour or so ago, it didn't seem clogged, but on a quick spin round the block without it, it seems to be behaving itself. I'm out in it tonight so will know better tomorrow. Many thanks for the contact

[BigOL]

Do not drive around without and air filter, although it maximises the engines airflow, it cannot stop any crap from flowing straight into the engine.

[Blackpug]

This is how I cleaned idle speed stepper motor on my car :

. Removed idle stepper motor to clean. It was covered in oily black gunk. You have to take cover off top of throttle housing. you do this by slackening a jubilee clip which you get to from the rhs of cover. Once off the stepper motor is small roundish thing with plug on it on rhs of throttle body. the stepper rod head can just be seen if you look down the smaller crescent shaped hole on throttle. The motor is held on by 2 torx screws. remove and clean rod with white spirit / turps. I used cotton buds and tissue.