8v Digifant Running Rich and RPM hunting!

[pommydubber]

I have been driving and doing up my 8v GTI 1990 RV code engine Golf for the last year or so. In that time i have had the head completely reconditioned and a high lift cam put in. 4 into 1 Tubular exhaust manifold (extractors for you aussies).
I have tested the Idle Stabilisation valve to check it's functioning properly according to the Haynes manual and it is. Also checked the infamous blue ECU water temp sender by unplugging it whilst the engine is running and it certainly makes the engine struggle until it gets plugged back in, so i guess it must be working. I have tried to make it idle around 850RPM by adjusting the allen screw in the Air flow meter but nothing happens from fully in to full out yet it runs and idles around 1000RPM.
I have also played with the fuel/air mixture screw but i can't seem to get the exhaust to chuff out anything but that sweet smell of overfuelling. The only thing left i can think of is the Lambda Probe is faulty.... Any other Suggestions???
Also when the aircon compressor is switched on and i blip the throttle the engine cuts out from being overloaded.

[Spyda]

As far as i know the screw on the MAF adjust A/F ratio.
The o2 sensor should be replaced every 160,000ks acording to the bently manual.

The idel is set using the screws on the throttle body but it gets a bit complicated, to do it properly you have to unplug the blue temp sensor, the car will strugle but thats normal. Then you have to rev it past 3000rpm 3 times, each time letting it drop to idel. This lets the ECU know you have unpluged the blue bastard. Then you adjust the idel screw to 1000rpm and plug the temp sensor back in. You can then switch of the motor off and back on and it should idle at 850. All fiddling has to be done at running temp, 80 degrees or something. Just wait for the fan to turn on and you know your at the right temp.

If the idle is hunting its usaly the ISV, soak it over night in brake cleaner that is rubber friendly, rinse it out and let it dry fully.

Im not guna tell you that this will solve the problem because in my experiense the idle on a digi mk2 is a head fuk and you just gota try everything.

[jayjay]

how big is the high lift camshaft you put in? if it's ridiculous, you'd most definitely have idling issues due to the duration..

but also what spyda said is quite informative.

[h100vw]

Spyda is correct the allen key is for the mixture. I bet the plugs are sooted up.

What cam do you have that will make a difference too. With some fettling though you can get even a 288 to idle properly.

Disconnecting the BTS and seeing a drop in revs doesn't mean it's working right. Get a new one if you haven't already.

Something else to look at is the idle bypass port in the throttle body. Remove the adjuster and check the O ring isn't damaged first. Then clean all the muck off it. I then stick them in a battery drill and polish them with some Brasso or metal polish. That stops the oil residue sticking so bad in future. Also get in and clean out the port itself. It will be gunged up, carb cleaner will work on that. Make sure the inside of the TB around the butterflies is clean too.

Then carry out Sypda's idle set procedure.

You should check the output on the lambda probe. Find the output wire, it might be a black one? Stick a voltmeter on it and start the car form cold. The voltage should start low IIRC and rise to about 1 volt as the engine warms up. Once up to temp you will see it cycle up and down between about .5V and 1V. If you are using a Digital Voltmeter, the readings will look a bit erratic due to the sampling rate but you should see the trend.

If it doesn't cycle, check the wiring first before buying new.

Gavin

[kkkevin29]

what does ISV stand for?

[h100vw]

Idle stabilisation valve.

Gavin

[benough]

We went through all those things on our MK2 but our issue was the low speed idle plug on the back of the throttle body. The pins were bent. Might be an easy fix.

[Golf Loon]

Yup, Spyda is correct, unplug the blue plug and set the timing by moving the dissy.
You should be able to get pretty close.
Then fine tune with the throttle body screws.

[mikinoz]

Im not guna tell you that this will solve the problem because in my experiense the idle on a digi mk2 is a head fuk and you just gota try everything.

Amen.

Check for vacuum leaks as a simple under tightened hose clamp or cracked pipe may be getting enough air in to affect the flow.

I am replacing the FPR on my car as I think that is causing me some issues with running rich.

Hope you can get it under control!

[pommydubber]

how big is the high lift camshaft you put in? if it's ridiculous, you'd most definitely have idling issues due to the duration..

but also what spyda said is quite informative.

The Camshaft is a Techtonics 272 Deg Duration. A bit lumpy on idle but nothing too fruity!