16v KR Setup with mods

Hi,

I've been having some issues setting up my 1991 16v GTi to make it driveable.

I've done most of the work on the car myself but was stumped on this one so took it to a VW specialist who charged me the money but didn't really improve things - I don't think they see a lot of these cars any more.

I followed some of the guides out there and noticed an unplugged vacuum line (which wasn't helping and I don't know how the garage could have set it up with the vaccum leak lol). Now that's in, with the ignition timing bang on, it purrs at a nice steady idle (just under 1000rpm) after messing about with the mixture and idle screw- an improvement from the wildly fluctuating and stalling idle I had before. I haven't tested from cold again yet - it'll probably hunt again when I do though.

The problem is that under light throttle (just enough to unload the idle switch) the engine stalls. It will rev past that point but creeping forward in 1st has to be done at 2.5k.

I'm getting a Gunson CO meter to check that fueling isn't wildly out (I know - not that accurate - but I can't drive it anywhere without it stalling and generally being a hazard).

There are some mods - it had a ported and polished head and a 4-2-1 exhaust manifold with the front silencer deleted, and just a K&N filter in the stock air filter housing. Will this change the ignition timing or anything else on the setup?

The answer, I think, is that it needs a rolling road setup with someone who knows what they're doing. I could trailer it there, but is there anything obvious I could be doing to at least make it driveable?

Thanks!

 

Have you checked the ISV?

 

Thanks, yes, that's what I thought too. Checked and replaced with new aftermarket isv before which didn't change anything.

Took it out yesterday - fine at wide open throttle but dipping the clutch plummets the rpm and stalls it.

Checked mixture - seemed OK with the gunson - around 1.8-2.0%. It's clearly not as accurate as a proper test station but I think I can eliminate it as a cause .

At idle it falls gently from 3k to idle though .

So - vacuum leak?

I sprayed carb cleaner (with fire extinguisher handy ) at the injectors (which have new seals anyway), and around the intakes - no change in rpm.

There are two vacuum tubes going into the car - what do they do and is it time to start hunting behind the dash?

 

The idle switch tells the ISV to operate (and let more air in) so when you accelerate the only air being drawn in is thru the throttle plate. Have you tried adjusting/opening the throttle plate with the ISV disconnected and seeing if you can get it to idle (at normal operating temp of course) ?

 

Have you set up the idle with the red/black wire disconnected?

One vac pipe goes to the ignition ECU under the scuttle the other goes to the dash cluster for the MFA

 

Thank you both - yes i thought I set idle with red/black disconnected but I'll double check it!

The engine stalls with the isv disconnected - so seems like an adjustment to the throttle is needed - sorry for the basic question but that's not the same as the idle screw?

 

Hopefully these might help

 

Looks awesome - thanks!

*searches forum rules for opening images*

 

Probably just being thick - but I probably need a certain number of posts?

 

Thanks rubjonny - yes that's one of my bookmarks on my phone!

I used that to setup - and I first thought my symptoms sounded like a vacuum leak but I couldn't find the source in the usual places and so I thought it could be due to the mods - but from the responses so far that looks unlikely.

I'll check the throttle adjustment Mervin suggested, then go through Sirguydo's diagnostic (if i can work out how to view the images) and double check by going through your guide again and report back!

It'll probably wait to the weekend as I'm not sure my neighbours with young twins would appreciate a revving gti engine on the driveway late at night!

Thankfully the Golf is more garage Queen than daily driver!

 

Hi,

Did some more tests today but same issue (stall at low throttle, fine at idle/high throttle).

ISV buzzing (it should do - it's brand new)

Overrun voltage working as it should (0v at idle and brief battery voltage when closing throttle from 4000rpm)

Diaphragm pressure switch also working (infinity ohms at idle, and when opening and closing the throttle resistance drops)

Vacuum lines with vacuum (can feel it/hear it when disconnecting the pipes)

All Coolant senders with a sensible resistance reading

On closer inspection of the throttle valve adjustment might be out. I moved the idle switch as far forward on its bracket as it goes, but there's still a gap between the throttle lever and stop. I think this might be the problem but can't find a way to adjust it any more.


I have attached (I think) a photo of what I mean. The gap by the red arrow is around 1.5mm, but if I read my Haynes correctly - shouldn't it be closer to 0.1mm? The yellow arrow is the bracket I have moved as far forward as I think it goes.

For the eagle eyed - yes the clamp is off the hose - but that's because I was messing about with the vacuum lines - it's not the problem

 

Doh! Of course lol

That's right though - around 0.1mm gap at the red arrow?

 

Cool - thanks for your time helping! Should be able to get that adjustment without bending anything .

At the moment the problem is stalling whilst the arm is between the green and red arrows when the accelerator is lightly pressed .

It's all fine at idle even without the isv connected .

Perhaps the idle bypass or switch is malfunctioning somehow? When the switch is pressed at about 3k the revs rise and the battery light comes on (battery stops charging) which clears with another engine rev.

 

Exactly what I wanted to avoid - wiring has never been my strong point! lol

I'll check it all over and see if I can recreate the weird response to pressing the idle switch whilst revving.