Mk1 problem, is it k-jet issue ?

**RedMk2Gti** · 26-08-2008, 08:55 AM

Car is Mk1 1.6 k-jet, the k-jet could be retrofitted, not original but Im not sure. It has been running ok but recently something is playing up.

It can be started when cold, no problem.. the problem is it won't idle well, begin with 700rpm then drop to 500rpm, nasty smooth

So far I've replaced all spark plug, lead, dizzy cap and rotor, air filter. oil, coolant, thermostat. Cam gear punch mark is line up with cam cover, dizzy rotor point to distributor mark, fly wheel 3 degree atdc is line up correctly.

I started thinking it is k-jet problem, aux air valve or warm up regulator. before I pull them apart, has anyone got any other opinion ? please help.

**Peter Jones** · 26-08-2008, 09:19 AM

I'd be trying to look for air leaks first. I had some similar issues with a faulty aux air valve. It had rattled itself to bits and was leaking from it's body.

There's a really good diagnostic info page listed back in one of the k-jet threads. Here it is http://www.auto-solve.com/mech_inj.htm

This will test you through how it all works and how to test the components.

Pete

**RedMk2Gti** · 26-08-2008, 10:43 AM

Thanks Pete
I've read that b4, I also have a library of k-jet book

but no practical experience

I vision checked all vacuum lines they all look intant. What instrument do I need to check for air leak ?

**Jarred** · 26-08-2008, 11:14 AM

Originally Posted by RedMk2Gti

Thanks Pete
I've read that b4, I also have a library of k-jet book

but no practical experience

I vision checked all vacuum lines they all look intant. What instrument do I need to check for air leak ?

WD40 sometimes works, but start ya bastard and those kinda things from repco etc are good. What you do is start the car, and then spray the "lube" on a possible air leak, and then if the idle picks up, there's probably an airleak there, if it doesn't help, move on to another suspect area.

I know this works for carby cars at least..

On another note, how does it run once it's warmed up (after 10-15 mins driving)?? any idle issues then?

**RedMk2Gti** · 26-08-2008, 12:59 PM

Originally Posted by Jarred

On another note, how does it run once it's warmed up (after 10-15 mins driving)?? any idle issues then?

I dare not let it run for that long cos the smoke in garage will kill me

**Peter Jones** · 26-08-2008, 01:02 PM

Just listen and feel around for the vacuum leak or as Jarrad suggests you can try spraying any suspect areas while it's running and see if there's a difference in engine pitch.

I suspect your aux air valve is working, as the revs are dropping back as they should. Normally they make the car idle fast until warm.

Perhaps your 5th injector isn't getting power. There should be 12v at the injector when the engine is cold. It's controlled by the thermotime switch on the head water outlet.

Another problem I've had is the idle speed adjustment screw in the throttle body working loose. This leads to the idle speed adjusting itself. This fix for this is easy. You just replace the o ring on the screw shaft. I used one from a multi pack of o rings I got from Bunnings for 99 cents.

Pete

**gldgti** · 26-08-2008, 09:53 PM

if its smokey on cold start but rough maybe its too rich? maybe 5th injector is working too much?

**Oneofthegreats** · 27-08-2008, 05:31 PM

Your cold start injector only work's when your cranking the engine, not when it's running as it get's it's power from the start supply from the ignition switch.

The temp. switch is the earth for this valve & only earth's it when cold, so you don't dump fuel in there on hot start ups.

If the cold start valve doesn't work it can make starting cold very hard & cranks over for a very long time but the idle should be the same.

Normally when an aux air valve gives up, the idle is very high around 2000rpm, as it can no longer close off the aux air supply pipe or if it has no power it will do the same. The aux air valve electrical plug's don't normally like the heat from the exhaust & eventually break.
But as Pete stated if it's creating an air leak, there will be other problem's.

Normally when the throttle body idle screw o-ring gives up, the screw mangages to unwind itself & the idle will go up. This has happened to me & it was very frustrating. You'd set the idle & with a couple of day's the idle would be around 1800rpm.

I've had all sort's of K-Jet problem's over the year's & they can be the simpliest fix's.

What fuel are you running? If it's ULP, the engine will idle slower as I have found out on many occasion's. Even it's a poor batch of PULP which I had on the way home from sydney, turned my car into a slug, incl. misfiring & eventually dropping down to two cyl's. Fresh batch of PULP, all good again.

Is there any air leak's?

The fuel filter could be blocked?

Check the CO%.

If you have to tool's you could check the system & control pressure's of the system, hot & cold to elimate part's like the warm up reg.

**Peter Jones** · 27-08-2008, 05:41 PM

Originally Posted by golfworx

Your cold start injector only work's when your cranking the engine, not when it's running as it get's it's power from the start supply from the ignition switch.

The temp. switch is the earth for this valve & only earth's it when cold, so you don't dump fuel in there on hot start ups.

I'll have to check mine now, mine was retrofitted and I suspect they got this bit wrong.

Pete