VR Idle hunting 11-1500 rpm + hesitation whenwarm(Now FIXED)

[Andy T 0]

last night my Vr's idle started hunting after going for a quick blast. It hunts between 800 - 2000 rpm every couple of seconds consistently, but never stalls. Driving at lowish rpm seems a bit jerky on and off the throttle.

 

When started from cold, the idle is perfect, then after a few mins it gets rougher, then hunts as above. Disconnecting the ISV made no difference at all. I've just unplugged the four pin MAF when running, it stopped the hunting, the idle dropped to about 500 rpm.

 

Can a faulty MAF cause this type of hunting when warm? I've done a search but found little on warm idle problems that aren't ISV related.

 

What else should I check? It's a late Coilpack VR6.

 

Cheers.

[Andy T 0]

Checked again, the idle actually hunts between 1100 and 1500 rpm consistently.

 

There is a hesitancy after pressing the throttle and a slight shunt a few seconds after releasing the throttle.

 

Anybody had these symptoms before?

[Toad 0]

Try the search mate, click on Advanced search, then type your criteria into the search box with a + if you want to include a term, and a - if you want to exclude somethine.

 

I'd go for something like +vr6 +idle +hunt

 

I click topics rather than posts, and off you trot...

 

This is a subject that's been covered a lot. :)

[Andy T 0]

Thanks for that, I've done alot of searches but didn't know I could use '+' in the seach text.

 

I've searched for hours now, also on vr6+TPS+idle etc, but come up with nothing about hunting/hesitation only when warm.

 

I've also tried unplugging the TPS when running, the hunting stops and it idles at around 1000 rpm. So both MAF & TPS have an effect on the problem.

 

The car will also idle with both unplugged, again at about 1000 rpm steady!

[ZippyVR6 0]

have you cleaned the idle stableizer valve?

[CorradoVR6-Turbo 0]

check that the isv pot is not cracked and drawing air in.

[Andy T 0]

Yeah the ISV was properly cleaned & lubed about six months ago.

 

I Checked all intake & ISV pipework for air leaks when running, but will check the ISV pot properly tonight.

 

Cheers

[Andy T 0]

Fixed! :D

 

Removed the ISV and all pipework - found the ISV shutter to be jammed open slightly, but not in the normal 'unplugged' position, the shutter had moved round to give a small opening on the other side. It didn't take much to free it up, maybe the shutter was moving slightly, causing the idle to go beserk. It also explains why unplugging it made no difference.

 

Found the insides of the ISV to be bone dry and slighly black, whatever I lubed it with last time has all but gone. Lubed it this time with a dab of thin engine oil, hopefully it keep it moving freely :)

 

She is running perfectly now, all idle & hesitation issues cured. The only thing I can't figure is why the idle was perfect when cold? :?

[mattkh 0]

Found the insides of the ISV to be bone dry and slighly black, whatever I lubed it with last time has all but gone. Lubed it this time with a dab of thin engine oil, hopefully it keep it moving freely :)

Hi

The black stuff can come off with carburettot cleaner.

The ISV should NOT be lubed.

[Andy T 0]

Found the insides of the ISV to be bone dry and slighly black, whatever I lubed it with last time has all but gone. Lubed it this time with a dab of thin engine oil, hopefully it keep it moving freely :)

Hi

The black stuff can come off with carburettot cleaner.

The ISV should NOT be lubed.

 

Yes I cleaned it with carb cleaner. I oiled it because it was recommended in several posts.

 

Why should it not be lubed?

 

I realise that it's probably way past its best now and will need cleaning often, otherwise it will jam again.

[mattkh 0]

Why should it not be lubed?

Hi

Thats what the guy at Bosch UK told me. It makes sense. All the oil and crankcase particles will jam the shaft.

[Andy T 0]

Why should it not be lubed?

Hi

Thats what the guy at Bosch UK told me. It makes sense. All the oil and crankcase particles will jam the shaft.

 

The lubed ISV lasted about 3 months, then the car suddently started stalling occasionally between gearchanges and idling low, and the low speed throttle hesitation came back. I've just fitted a second hand ISV that was in good nick, just cleaned and not lubed this time!.

 

The idle is back to its normal smooth self, but i've still got the hesitation issue, on and off the throttle at low speeds, when engine is either cold or warmed up. :(