Strange engine Idiling problem

PeteB_2000 · 05-23-2008, 06:01 PM

Hello again

After my timing belt change the engine is now idiling at around 1000 revs...strange thing is if my depress the foot brake it drops to a more "normal" 750revs foot off the pedal and it goes back up

Any ideas what may be causing this ??? is it coincidence ??

All help graciously received

Pete

Steve1234 · 05-23-2008, 09:37 PM

You should probably change your timing belt again.

Hahaha - but seriously, are you talking about when in drive? Or parked in neutral?

ron1004 · 05-24-2008, 02:46 AM

My guess is that you have an intake manifold vacuum leak - check all the vacuum hoses and listen for the suction hissing while idling.

PeteB_2000 · 05-24-2008, 09:23 AM

just sat in neutral with the engine running up it shoots to around 1000 press the brake and it comes down to what IMO it should idle at around 750

PeteB_2000 · 05-26-2008, 06:23 AM

not noticed any hissing noises guys anymore ideas?

sedona no 1 · 05-26-2008, 07:53 AM

It does sound like a vacuum leak from somewhere as when you press the brake, it is also using the vacuum but if too much air is getting to the air intake without pressing the brake then the revs will shoot up. Could be a split in a pipe somewhere. Check the vacuum pipes coming from the alternator, air intake and the air tank on the bulk head.

PeteB_2000 · 05-30-2008, 06:41 AM

ok SN1 will have a mooch around the engine bay

TEXKIATECH · 05-31-2008, 08:18 PM

just gat like two cans of carb cleaner and spray your engine all over till you hear it die down then you have found your vaccum leak. i would check the brake booster line first

ron1004 · 06-01-2008, 03:31 AM

Quote:

Originally Posted by PeteB_2000

just sat in neutral with the engine running up it shoots to around 1000 press the brake and it comes down to what IMO it should idle at around 750

Inspect the non-return valve in the vacuum line going to the brake booster.

93fxdl · 06-02-2008, 08:56 AM

things seem a bit confusing here on a petrol engine the brake servo is fed by vacuum from the inlet manifold but pete yors is a diesel so there is no manifold vacuum to feed the brakes it is supplied by a separate pump which i believe (could be wrong mind you)
is attached to the alternator or it could be a separate pump sorry but i cant be any other help but it sounds as if putting the brake on is putting extra load on the engine either electrical or the vacuum pump a couple of tests to see where the load comes from 1 disconnect the brake light switch and try again if no improvement fault is in the vacuum system 2 disconnect vacuum pipe from pump and test again
another possibility is something haywire in the engine management but what do i know
ttfn glenn