New idle control valve - now engine goes mental...

[Mike16v 10]

Any help much appreciated...

 

Fixed the sunroof, electric mirrors, spoiler, sunroof - just want to drive it now but I can't :(

 

I've got a 1993 16v and since I bought the car, the engine has idled between 1.5k - 2k revs.

 

Here are the things I've done to try and sort it:

 

New cat and lambda sensor

New coolant temperature sensor

Throttle body cleaned

New Idle control valve

Checked throttle cable

 

I changed the ICV today and a strange thing happened. When I started the engine, it still idled at 1500. Checked to make sure the switch on the throttle body was clicking when the throttle was closed, and I could hear it. Took the car for a quick drive to see of things would calm down. There was no change. Later, I started the engine again and it went straight to 5k revs and stayed there.

 

My next step is to change the throttle body switch in case that is duff. Should the odd behaviour after changing the ICV be telling me something?

 

I really don't want to admit defeat and book it in to the garage, but other than the throttle switch, I'm running out of ideas.

[CazzaVR 0]

Have you checked all the air hoses thoroughly e.g. behind, underneath etc?

[davidwort 0]

vac leaks usually lead to stalling as too much unmetered air and not enough fuel (metered by the air flap before the throttle body) is getting into the engine, it's worth checking all the vac pipes thoroughly though as CazzaVR says and also any potential leaks in the inlet manifold.

are you sure your throttle cable and throttle butterfly work smoothly and shuts OK?

 

It sounds like your ISV just cant restrict the revs at all, I had this happen with an old one, but taps on the throttle usually settled it (just sticking) there's a possibility the wires to your isv throttle switch are broken, you need to get a simple multimeter and check the circuit is making/breaking

[Mike16v 10]

Thanks chaps.

 

I've just taken the switch off the throttle body and tested it. There is continuity between the centre pin and the outer on with the spindle turned all the way in on direction. The circuit is broken when turned away from this position. This is pretty much what I was expecting it to do. I think its just an on/off switch on the 16v engine, am I right? At least it look like I don't need a new one - they're £100+new, ouch.

 

I've checked all the hoses for leaks using carb cleaner but not a sausage.

 

I'll check the wiring to the ICV next.

[davidwort 0]

what does it do if you unplug the isv or idle switch altogther?

[Kevin Bacon 5]

5000rpm idle!!! Are you sure you haven't just got a stick throttle cable holding the butterflies open?

[Mike16v 10]

You would think Fishwick, but the cable moves freely and the throttle snaps back all the way closed. There was no hint of the throttle sticking open when I had it off the car to clean it. Am I right in thinking the throttle should be completely closed, and the switch kicks in the ISV?

 

The really high idle only happens after driving for a while and switching off. When I restart the engine is revs right up - I just don't understand it. If I disconnect the ISV for a couple of seconds it calms down to 1500. Still too high obviously.

 

I'm thinking more and more that it's an electrical problem rather than a faulty component. Scratching my head though...

[Mike16v 10]

So it turns out that my 'new' ISV is a duff one. Today I cleaned and refitted the old ISV and the engine ran fine. Might not last long, but at least I know what was at fault. The ISV I bought on ebay was supposedly new but on closer inspection looks decidedly reconditioned. Guess the lesson learned is you get what you pay for.

 

Has anyone managed to take an ISV apart and give it a proper clean? It looks well and truly sealed to me.