Car Idle speed suddenly very fast

[JediGoat]

I took my 10 year old Renault into Autoglass this morning for a replacement windscreen. As I left, I thought they'd pushed the mat under the accelerator pedal as it seemed to only go part way down (and the car didn't quite feel 'normal'). When I stopped at the traffic lights I pulled the mat back and set off again.

It wasn't until I went to brake that I realised the engine was really racing. When I stopped, the idle speed was between 3-3.5k (normally about 1-1.2k), and if I blipped the throttle, it just went up higher (4k RPM - which is higher than recommended for any gear other than 5th!).

I've never had any mechanical problems with this car (although plenty of electrical issues), and the throttle/idle speed have never had a problem. If anything, the idle was possibly a little bit low.

I've called them and am taking it back in tomorrow for them to look at it, but does anyone have a clue what it is they could have done that has caused this?

I've rather annoyed about it as the car is due for it's MOT next week, and if this is going to cost me any money to fix, then I'll have to just sell (or scrap) the car instead.

Thanks in advance.

Jo

[Luckypants]

Unlikely that changing the windscreen will have affected anything mechanical. It may be that a bit of debris (glass / sealer / etc) has fallen into the accelerator mechanism, jamming the throttle open. As you state that the accelerator only goes 'part way' I'd say that supports the theory, as some of the accelerator movement already taken up. Follow the cable from the accelerator and look for something jammed in any of the moving parts of accelerator / cable / throttle linkages etc.

but does anyone have a clue what it is they could have done that has caused this?

Dont assume it was them just because if the timing.

[JediGoat]

Originally Posted by beabert

Dont assume it was them just because if the timing.

Yes I can understand that, it's just amazing timing that it was working fine when I took it in, and not fine immediately they gave it back.

The 'something jammed' sounds feasible, or I thought maybe they have bent the pedal. But the revs do drop when I'm moving along, they just soar again when I'm not pressing the pedal.

If it has a throttle body maybe a vaccum pipe has come off, same happened with my astra

[Spiderman]

I'd go with a sticky throttle cable as Luckpants said above. Weather its from bedris of their work or just a coincidence that the cable has decided to give up the ghost now after 10yrs of service.
its the fact that the pedal isnt moving easily that leads me to this and not vaccum hoses etc ....tho of course it could be those if the cable is fine and moves freely.

HTH jo, good luck.

Why is 4k revs not recommended in anything other than 5th gear?

Is it fuel injected or carb, and if it is carb is it manual or automaticm choke?

[JediGoat]

Originally Posted by svdemon

Why is 4k revs not recommended in anything other than 5th gear?

Recommendation (which I think is with many cars) is that you don't hold steady revs for too long above 3.5k in any gear except 5th. Don't ask me why, I have no idea. What I do know is that I sound like some impatient muppet at traffic lights

Originally Posted by shifter

Is it fuel injected or carb, and if it is carb is it manual or automaticm choke?

It's fuel-injected. I just got home and tried it again and it's starts fine but idles at just over 2k, and after blipping the throttle, it goes to 2.5k.

Autoglass were very nice when I called them about it - I felt a bit daft as how could a change of windscreen cause this? I can't really believe it myself, but it is incredibly freaky that it has never happened before, and only happens immediately after they had the car.

They will have a look at it tomorrow in case it was something they did, which I'm grateful for. If anyone hears what they think is a boy-racer heading towards Hendon early tomorrow morning....it's me

Jo

wd40 the throttle cable.