Idle valve

[993Type]

The appropriately named idle valve has decided to only work part time.

Took the car for a run last week and when stood at lights, idle RPM flicks from 1K to 2K like I'm sat there revving it for attention!

Upon disconnecting the idle valve, revs settle to steady normal 900RPM or so.
Car is a varioram.

I am assuming it's the valve itself but has anyone else had this happen?
Also, once the valve is electrically disconnected, everything runs fine, any issues with just running the car without reconnecting it electrically or bypassing it??

I've taken it off this weekend and thoroughly cleaned it with white spirit and it's moved easily when rotated, I don't think it's actually that old, maybe replaced about 5 years ago.....

Don't mind replacing it now I know how but loathe if it's not adding anything useful to operations.....

 

[Gwsinc]

Clean it out with carb cleaner, it's the only thing that gets all the grime out.

Its natural rest position is slightly open so you will idle with it unplugged but the idle won't be adjusted as the ecu demands so will fluctuate, I'd give it a good clean with carb cleaner or replace if issue persists. There was a post not long ago about an aftermarket ICV for £60 or so from Germany, I've been running one for a few months now and no complaints...

Link: https://maf-shop.com/shop/iac/porsc...sche-993-ferrari-repl-99360616000-0280140543/

Same item also available on eBay..

 

[993Type]

Many thanks, found that post just after mine that you refer to and it's very interesting!

I've read that once they start to get sticky, it might be time to consider a new one, at £60 it's a no brainier so I'll order one.

I'll soak my old one in carb cleaner when off but it was clean as a whistle after the soaking in spirits so think it's shot...

 

[993Type]

Edited for double post....

 

[Heuer]

Just had mine off the car and gave it a thorough shampoo with brake cleaner, panel wipe and FE10 switch cleaner. Whilst it now seems free it does occasionally stick when I twist it. Ordered a new one from MAF Shop because at £55 delivered with three year warranty it is probably cheaper than buying the chemicals! Cleaning was the best option when the Porsche part was £600 but at a tenth of that may as well fit a new one every few years.

 

[tel0020]

Idle Valve

Mine did a few years back.

When off and you flip it back and forth there will be lack or movement but afterwards it will be free as a bird!

Very easy to get it off and clean with Carb Cleaner and cloth
Right at the top of the Engine under the bulkhead in the centre.
Getting Jubilee Clips off can be interesting depending how there was last put on

Took all of 30 mins from start to Finish.

Graham

 

[Heuer]

Make sure you check the operation of the ICV with a 12v battery before reinstalling. They can lock up even after cleaning and the stepper motor sometimes fails on one winding. 12v positive to centre terminal, -ve to side terminals in turn. You should hear a click as the valve rotates one way and then the other.

Also the ICV is a precision device and runs in two bearings which suffer from wear and means even after cleaning the valve can jam intermittently because the tolerances are tight. I was told you can clean it once but after that replace if the symptoms (stalling, idle fluctuation, increased idle rpm etc) return.

Finally apply some red rubber grease to the fittings to both preserve the rubber and make fitting (and future removal) so much easier, about £3.50 for a small can off eBay.

 

[Heuer]

The replacement ICV is stamped and boxed as 'Lowe Automotiv' and is basically the same as the Bosch one.

Giving them both a gentle shake reveals the original is still not as free moving as the new one despite the cleaning. Installed in less than 10 minutes with the aid of the rubber grease and a £5 7mm hex flexible shaft hose clip driver from Amazon as recommended by a member here. I orientated the back hose clip with the nut on the right for even easier access:

 

[993Type]

Thanks for all the tips!!

Aaaghhh!

Cleaned my Bosch valve to surgical levels, refit - same pulsing up and down on idle.

Ordered the German valve (FANTASTIC TIP, thank you! AND ALSO FANTASTIC SERVICE FROM THE SUPPLIER).

Fit this valve today, 10 seconds consistent idle and then pulsing again.

Also replaced the front boot that had a little tear in it and I could hear the vacuum loss through.

Battery disconnected for 10 mins to allow all levels to be set......

Idle pulses up and down.

Disconnecting the valve creates a steady idle and also makes the car drivable.

Quick questions -

(1) Any ideas what to look at next?
There aren't obvious vacuum leaks but I will put a meter in to check (the strength of vacuum actually really surprised me).

(2) Is it safe to run just with the connector disconnected, except the car is restricted but only on idle (don't want to run hot or upset the down steam stuff, bit of extra fuel use is fine).

Next stop is Strasse but they are a good hour away and was hoping to drive it through if I can't resolve local, I might be at the end of my technical envelope in terms of sorting (it's one of those really tiny envelopes that's only a bit bigger than the stamp itself......i

 

[Gwsinc]

I've heard of the Throttle Position Sensor causing issues like this. You can get a % open readout using a T-OBD or some other scan tools, from memory should read 4% open with throttle closed and anything over 80% is wide open throttle.

Perhaps also try unplugging the MAF, if it stops pulsing then that's your issue.

 

[993Type]

Thank you, is that behind the varioram just after the air filter?

My next thought is that the airbox filter is slightly loose and it might be spoofing the MAF into reading the wrong amount of air, so will check this out.

 

[wilsonny]

Thank you, is that behind the varioram just after the air filter?

My next thought is that the airbox filter is slightly loose and it might be spoofing the MAF into reading the wrong amount of air, so will check this out.

If you've had the back section off the air filter housing, it's really easy not to get it back connected right. Did this myself and it caused a bit of uneven idle running.

 

[Gwsinc]

Thank you, is that behind the varioram just after the air filter?

My next thought is that the airbox filter is slightly loose and it might be spoofing the MAF into reading the wrong amount of air, so will check this out.

Yes the MAF is next in line after the air box, round connector. The air filter paper element can sometimes detach from the white foam surround, so check this too. Otherwise, as above, make sure the maf is firmly connected to the air box and the air box lid slides firmly into the housing with both clips sealing the front.