engine revving on its own

B

Buckym120

Member
Evening all had a pretty scary evening tonight and i've search and looked through the problems post and cant find anything similar.

Tonight i was driving along put my foot down a bit and as i changed gear pressed the clutch down and the engine began to rev on its own, changed into 4th (thinking i had caught the accelarator in error) and when in 4th the car shot forward an began to accelarate hard. Went into neutral and it revved round to redline, went back into 4th and again it continued to accelarate as if the throttle was stuck open. went into neutral again and it began to rev round to the redline again so turned the engine off and then had to brake hard as i was approaching a roundabout (brake pedal is now rock solid and has no movement, so guessing i've done the master cylinder, but will worry about the later).

once i was pulled over started the car and it began to rev high straight away heading towards redline. all pipes appear to be ok, the throttle cable and linkage looks and feels like it is hitting the stoppers and not sticking. i've unplugged the maf which stopped the car from revving to the limiter but sat around 2k and was running rough.

I've recently had the manifold/turbo off to replace the gaskets so not sure if i have disturbed something.

sorry if the above makes no sense its 2 in the morning and i;m shattered
 
PobodY

PobodY

Moderators
Staff member
With the engine off you've got no vacuum assist on the brakes, so that's why they'll feel rock hard; you'll get maybe one good pump before any vacuum is gone.

Is it possible the throttles are stuck open? You've checked the linkages etc so probably not, but it's the obvious thing that would cause the engine to do that.

Take a look at it in the light today and take photos of anything you think looks off?
 
B

Buckym120

Member
Cheers for replying mate.

They appear to be opening and closing when looking at the linkage (hitting the stopper when released)
Could a faulty maf cause the above symptoms?

I'll collect my gready meter and plug in tonight to try and see the throttle position


With the brakesi had no pedal movement when the engine was running as I had to drive home with the maf off.
 
B

Buckym120

Member
Cheers for replying mate.

They appear to be opening and closing when looking at the linkage (hitting the stopper when released)
Could a faulty maf cause the above symptoms?

I'll collect my gready meter and plug in tonight to try and see the throttle position


With the brakesi had no pedal movement when the engine was running as I had to drive home with the maf off.
 
red reading

red reading

Active Member
air leak by the sounds of it, all the big vacuem pipes are under the trottle boddies and a bitch to get to, and it will be a big air leak to do what your car is doing.
 
J

j0ff

Member
if it's revving and has enough power to propel the car forward as though you've got your foot planted, then it cant be a simple vacuum leak - it has to be the butterfly's are stuck open somehow.
 
J

j0ff

Member
or... has the vacuum pipe to the master cylinder become disconnected? (I assume this is engine side of butterfly valves)
 
bensmith907

bensmith907

New Member
As danny says I would look for a vacuum leak under the tb's. a simple leak can deffo cause this as Ive had it before.
 
P

pulsarboby

Guest
its more than likely the throttle position sensor mark

just read your post again also about brakes.....check the solid vacuum pipe to servo unit has not blown out the rubber seal as that will cause your servo to not work and brakes feeling solid
 
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B

Buckym120

Member
tried to have a quick look tonight but buy the time i was home it was dark, unpluged the tps to see if the problem continued and it wanted to rev again so looking more like a leak some where
 
stumo

stumo

Active Member
Sounds like the vacuun pipe has either come off or has a big split in it as your brake pedal was hard even with the engine running which indicates the servo isn't getting any vacuum AND your revs were going skyhigh which also indicates an air leak even with the throttle pedal not pressed.
 
PobodY

PobodY

Moderators
Staff member
How is it getting the fuelling if it's a leak on the other side of the throttle bodies?
 
B

Buckym120

Member
well tonight i've seperated the rubber and solid pipes going to the brake servo and there was a slight vacum but not consistant (car was idling at 2k rpm) and the car was still experiencing the same issues, but at least it rules out the servo and rubber. Next to check the rubber going into the manfold. to make life easier i thought i would remove the top half of the inlet manifold and this also gave me the chance to check the throttle bodies incase the butterfly had jammed open.To my amazement i've found something lodged in the first throttle body, preventing the butterfly from closing. Dont know exactly what it is yet as i haven't removed the blockage, but will do it tomorrow after work and update here but believe i've found the problem. just hope its not broken up into the block and i can remove in one piece
 
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vss irvine

vss irvine

Well-Known Member
id check your turbo too then, depending on if you can work out what it is and where it might have come from.
 
B

Buckym120

Member
heres an image, i'm normally really careful taking pipes off and any exposed area on the car i block with a cloth to try and prevent this from happening (unless this object was on the cloth when i blocked the inlet manifold/intercooler pipe work.

Do hope it hasn't been pulled through the turbo as mine had no play when i reinstalled it. Aalthough looking at the size of it i doubt it would have gone past the turbine and would have got tangled up


 
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