K-jet Idle speed changing...

For all Carb and Injection engines, standard or modified plus non-standard engine transplants. Heads; Blocks; Cooling (including heater issues related to the cooling system); Mounts etc

Moderator: Scirocco Register

Forum rules
Hints, tips and guides for repair and modification - the FAQ section on the main website is worth checking first for information relating to common faults and technical help. Useful posts and guides will be added to the FAQ http://www.sciroccoregister.co.uk/scirocco-faq
JackPong
Posts: 29
Joined: Thu Jun 18, 2015 11:49 pm
fill in the right answer: 15

K-jet Idle speed changing...

Post by JackPong » Tue Mar 01, 2016 3:54 pm

Got the Idle speed down from 1300 to 950 last summer; cleaned metering head, air filter, throttle body. Ran lovely like this for several months.

Car was then laid up for maybe 4 months.

On bringing her out of hibernation the idle speed has now dropped to 200-300 but occasionally, usually after a brief period of high revs, the Idle speed will return to around 950 then when clutch depressed or car stopped and restarted Idle speed drops to 200-300...

Cleaned the metering head again, plenty of fresh fuel over 800 miles this year. Should mention that the screw to adjust Idle on throttle body is fully closed (due to previously reducing Idle speed)

Any ideas..? Sounds like something is sticking...

Saw the forgotten GTX resto thread and thought maybe a faulty microswitch. Bit expensive if it's not €45 + shipping

Thank you for help :-D



User avatar
bluestreak56
Posts: 616
Joined: Wed Apr 01, 2009 11:59 am
fill in the right answer: 10
Location: West London

Re: K-jet Idle speed changing...

Post by bluestreak56 » Tue Mar 01, 2016 5:39 pm

Typically I often had to adjust my idle screw to get the right level as like yourself my car wasnt used frequently or if so was doing very short journeys..


Image

JackPong
Posts: 29
Joined: Thu Jun 18, 2015 11:49 pm
fill in the right answer: 15

Re: K-jet Idle speed changing...

Post by JackPong » Wed Mar 02, 2016 9:45 pm

She gets used pretty regularly. 800+ miles in last month...

Had a weird one this evening. Parked up with headlights on and Idle speed was hunting in a mesmeric fashion between 200 and 600. Turned the lights off, then on and idie settled to its regular 200-300 rpm

Gonna try bringing Idle speed back up to 950 with the screw and see if strange going ons persist.



mark1gls
Posts: 3614
Joined: Thu Apr 02, 2009 9:28 pm
fill in the right answer: 10
Location: Somerset

Re: K-jet Idle speed changing...

Post by mark1gls » Thu Mar 03, 2016 1:56 pm

Could be the rubber seal on the idle jet is old, hard and flat and letting in air or working it self lose over time. A new o-ring is pence so may be an idea to replace it?

Pictures... If the need to size of the o-ring let me know as I took some measurements.
My old one fitted and my screw used to work it self lose.
Image

New one fitted.
Image


Mk1 78 Scirocco GLS 1.6 FR, weekend toy.
Mk1 88 Golf GTi cabriolet 1.8 DX. Daily drive.
Membership No. 323

JackPong
Posts: 29
Joined: Thu Jun 18, 2015 11:49 pm
fill in the right answer: 15

Re: K-jet Idle speed changing...

Post by JackPong » Thu Mar 31, 2016 11:32 pm

Had a minute to check this out. O ring felt OK.

Business end of screw was encrusted with hard black stuff. Carbon build up maybe. The entire intake system was covered in it when I got the car.

Carb cleaner wouldnt shift it.

Image

Stuck it on my mates burnishing wheel. Came up a dream.

Image

Had the throttle body off, but impossible to clean the airflow channel inside casting...

Idle reset and hasn't wondered since.



daveyheats
Posts: 49
Joined: Sat Oct 24, 2020 6:35 pm
fill in the right answer: 15
Location: Stroud, Glos

Re: K-jet Idle speed changing...

Post by daveyheats » Sun Jan 10, 2021 9:04 pm

mark1gls wrote:
Thu Mar 03, 2016 1:56 pm
Could be the rubber seal on the idle jet is old, hard and flat and letting in air or working it self lose over time. A new o-ring is pence so may be an idea to replace it?

Pictures... If the need to size of the o-ring let me know as I took some measurements.
My old one fitted and my screw used to work it self lose.
Image

New one fitted.
Image

Sorry for digging this up from years back mate, but do you remember the size of that o-ring? Will be slapping a new one on mine but don't have it to hand.



mark1gls
Posts: 3614
Joined: Thu Apr 02, 2009 9:28 pm
fill in the right answer: 10
Location: Somerset

Re: K-jet Idle speed changing...

Post by mark1gls » Mon Jan 11, 2021 12:08 am

I did take some pictures of the size of the o ring but I can’t find them tonight, give me a day or so and I’ll see if I can find them for you.


Mk1 78 Scirocco GLS 1.6 FR, weekend toy.
Mk1 88 Golf GTi cabriolet 1.8 DX. Daily drive.
Membership No. 323

mark1gls
Posts: 3614
Joined: Thu Apr 02, 2009 9:28 pm
fill in the right answer: 10
Location: Somerset

Re: K-jet Idle speed changing...

Post by mark1gls » Mon Jan 11, 2021 9:50 pm

Found the pictures, the I ring is rubber so tricky to get a measurement but it will give you an idea.

I did have to smear a little grease on mine to be able to slide it on.
Image

Out side measurement

Image

Inside measurement


Sent from my iPhone using Tapatalk


Mk1 78 Scirocco GLS 1.6 FR, weekend toy.
Mk1 88 Golf GTi cabriolet 1.8 DX. Daily drive.
Membership No. 323

daveyheats
Posts: 49
Joined: Sat Oct 24, 2020 6:35 pm
fill in the right answer: 15
Location: Stroud, Glos

Re: K-jet Idle speed changing...

Post by daveyheats » Sat Jan 30, 2021 6:08 pm

Meant to say thanks for this mate! Ordered a new o-ring and it's now on the idle jet. Hoping it'll help out idling issues when I get round to finishing off the current jobs and starting her up again.



mark1gls
Posts: 3614
Joined: Thu Apr 02, 2009 9:28 pm
fill in the right answer: 10
Location: Somerset

Re: K-jet Idle speed changing...

Post by mark1gls » Sat Jan 30, 2021 10:24 pm

Glad it was some help.
If you do find the idle screw moves and your idle speeds drops at any time you can wrap a bit of PTFE tape around the thread as I’ve seen a few do this, I’ve not had to on mine though.


Mk1 78 Scirocco GLS 1.6 FR, weekend toy.
Mk1 88 Golf GTi cabriolet 1.8 DX. Daily drive.
Membership No. 323