Revs won't die off, what's wrong?

[Rob669]

I've noticed when I take my foot off the throttle the revs aren't dying/dropping as quickly as they should be. Also the revs drop and then rise slightly again.

The cable isn't sticking and the throttle body opens and closes just fine. I reckon it's a sensor fault. The car (it's a 172) is always run on Optimax/V Power or superunleaded. Anyone know what the problem could be?

Cheers, Rob669

 

[Russ_16v]

whats the revs dropping and rising too mate?

mine was revving itself between 1000-3000 rpm then holding at 3k

turns out i needed a new idle control valve

it sticks a lil sometimes if i drop revs slowly,and its fine if i give it a quick rev,on mine its where the cable attches to the throttle body sticks ever so slightly,not the cable itself but the actual lever mech that operates the butterfly,when its holding the revs up get out,pop the bonnet and push the black lever that the calbe is attached to,that should stop it

 

[S22 JGS]

clutch on its way?

 

[Rob669]

The revs rise only a little, nothing like as much as 3000 rpm, and then they drop down fine to normal idling speed - it's just that slight delay and it's noticable. I am suspicious of that long black part before the black lever - the adjuster. Maybe I'll fit a new cable and see if that sorts it.

Cheers

 

[Rob669]

Clutch! Don't say that, it's expensive.

Can't see how it can be the clutch TBH. It doesn't rev as cleanly as it should I reckon with or without the clutch engaged.

 

[Sami]

How do you know the cable isn't sticking? or is it electronic throttle lol

 

[Rob669]

It's phase one so it's a cable operated type. It doesn't feel sticky. But I do not for certain. Only way to find out will be to replace it, I guess.

Cheers, Rob669

 

[Sami]

You can't really feel if its sticky, I had one go on my car few months back, I started noticing when I changed gear as it was revving up turned out the cable was properly shafted, it snapped eventually!

 

[Rob669]

Cheers. New one it is!

Rob669

 

[Sami]

Before you do that try dripping some oil down it, see if that helps?

 

[AlexS]

Mine does this alittle sometimes too, if you floor it and take it up to just before 6k, lift off, change sometimes the revs increase a little in between changes, but mines electronic throttle...

 

[Dan@SJM]

mine was idle control valve, its quite common.

 

[LegoHead]

mine was idle control valve, its quite common.

where is this on a 182 engine?

 

[Rob669]

Cheers Dan.

Rob

 

[ChrisR]

Oddly mine used to do this but has stopped, can't remember exactly when it stopped but could tie in to when i had the inlets replaced.

It'd hang at 2.5-3k as if i had my foot resting on the pedal, then if i blipped it or even jsut nudged the pedal on it's side the revs came down so guessing that was a sticky cable.

 

[edde]

mine was idle control valve, its quite common.

where is this on a 182 engine?

There isn't one Mk2 phase 1 only.

 

[BrianR]

Distorted throttle body.

I had this happen and I changed a perfectly good cable for a new one before I found the problem.

Only does it when the engine warms up.

 

[LegoHead]

Distorted throttle body.

I had this happen and I changed a perfectly good cable for a new one before I found the problem.

Only does it when the engine warms up.

Mine only does it after the engine is warm! If i let it cool down for a few minutes before switching off its fine when i restart say 10 minutes later.

So its probably sticking due to distortion of the body?

 

[Rob669]

Distorted throttle body.

I had this happen and I changed a perfectly good cable for a new one before I found the problem.

Only does it when the engine warms up.

Ok, thanks. So is the cure a new throttle body?

Rob669