Citroen Saxo (1997 - 2003) - 99 1.0 Random Revs pull car - Throttle position se

Honest John Back Room » Technical matters
View Threaded
Sun 13 Dec 2009 14:14
99 1.0 Random Revs pull car - Throttle position se - tom1066
Hi there,

I'm prone to waffle so I'll try to keep it short!

I've read the related threads on this subject and think the problem is either the Throttle Position Sensor, gunk in the Knock sensor...

But I know virtually nothing about cars...

The biggest clue I have (red herring?) is that the problems started immediately after I had a 'Repair' pipe fitted to the exhaust. I've just spoken to the guy who fitted it and he said that is the proper name for it and there are no sensors in that bit...

Anyway here are the symptoms:
-------------------------------------

About 10% the car is fine (particularly when the air is very dry?).

70% it just revs too high, but will sometimes drop back down to normal revs for a while. Sometimes the revs are strong enough to drive the car along by itself in gear with no throttle.

20% it will rev up and down like a boy racer waiting at the lights. This results in difficulty crusing along at low speeds with minimul throttle input as the car will 'bunny hop'.

It's not consistent and will vary during a journey.

NB Also independant from what the revs are doing if I'm holding a cruise speed the power/torque will frequently just vanish until I either press the throttle down until it 'catches' again or just quickly de-clutch like I'm changing gear. It seems to do this at higher speeds. 30mph+


I don't think that it's the ICV as the car can drive itself.

I suspect the exhaust work possibly got gunk into a sensor somewhere but the man from the garage hasn't even heard of a Knock sensor...

So over to you guys if anyone thinks they can isolate a problem I'd be very grateful!

I'm skint and am scared to let a garage loose on it as others on these threads with similar problems have changed loads of different parts before solving the problem.

Thanks in advance.
Sorry for the waffle!

Tom.
Reply | Report as offensive | Link
Sun 13 Dec 2009 16:56
99 1.0 Random Revs pull car - Throttle position se - injection doc
idle speed control valve are the most common on these. check that all the vacum pipes are all properly connected.
Reply | Report as offensive | Link
Mon 14 Dec 2009 18:33
99 1.0 Random Revs pull car - Throttle position se - tom1066
Thanks for your response.

Other people seem pretty sure that if the car can drive itself then it can't be the Idle Control Valve, and that the ICV only regulates an idling car or a car with a cold engine...

Today on the drive home it was very humid/raining and was playing up the whole way right from when I started the car. Revving up and down or just high revs. Even with a warm engine. I came most of the way home at 30mph in 4th gear with no throttle needed. Drives itself at low revs/torque, bunny hops at higher revs.


Reply | Report as offensive | Link
Mon 14 Dec 2009 19:32
99 1.0 Random Revs pull car - Throttle position se - injection doc
a faulty idle control valve will certainly drive the car along for you. I have known those to make the rev's hunt up & down to 3000 rpm
Reply | Report as offensive | Link
Mon 14 Dec 2009 19:55
99 1.0 Random Revs pull car - Throttle position se - tom1066
Thanks for the reassurance. I'll kick off by getting a new ICV.

Does the fact that the problems only started immediately after I got a 'repair' pipe fitted to the exhaust set any alarm bells off with you?

About how much do you think getting a new ICV fitted should cost?

Thanks for your help.
Reply | Report as offensive | Link
Wed 2 Feb 2011 13:36
99 1.0 Random Revs pull car - Throttle position se - alwaysblue

i am having the same problem iv replaced gaskets plugs now im told its the idle speed control but its had one of them to the diagnostic thing said thats the problem but you can here it sucking air in if you spray the engine with brake fluid it runs fine any ideas what the problem could be :( thanks

Reply | Report as offensive | Link

Looking for a garage you can trust? Honest John's Good Garage Guide has thousands of reader recommended garages, plus how-to guides and tips on servicing.

The Good Garage Guide