A Digi2 that doesn't idle.. Again..

[Mongoxcore]

I've been lurking around on here long enough to know that crap idle digi2 threads are played out beyond all else.. But a man can only take so much before he breaks down and post's one..

8v 89 Golf Digi2. It just cant idle when the hose that goes between the ISV and the intake tube is connected..

Tube disconnected: Upon start up it finds 900rpm wether cold or warm, but only for about 3 seconds. Then it decides to give up and rpms drop, battery light comes on for less then a second and is followed up by the ever popular surge between a couple hundred rpm's and 2krpm. Eventually it decides it likes 1.8-2krpm and sits there for idle.

Tube connected: Upon start up it finds 900rpm wether cold or warm, but only for about 3 seconds. Then it decides to give up and dies. The end.

New temp sensor, new o2 sensor, throttle body cleaned and readjusted, every vacuum line I know of replaced, grounds cleaned, 4 gage for negatives, maf cleaned, new cap and rotor, new spark plugs/wires. I even have 2 ISV.. Cleaned and tried both, same results.

Timing is spot on. I do need new lifters though(Bought along with tt cam, soon to replace.)
New maf? New wire harness?

This baffles me as when i bought the car it had a crap idle and being that I had already been reading up on digi2's here before buying it I replaced the battery negatives not more then 2 days after owning it, curing the crap idle.. Then suddenly it came back with a vengeance.

I've yet to really do anything fuel related, aside from the russian roulette that is stp fuel system cleaner, and haven't played with any of the 'positive' wiring..

Any help would be much appreciated.

[spoon!]

Whatever you do, don't disconnect/reconnect the ISV harness connector with the engine running. You can kill the ECU.

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First off, connect everything like it's supposed to be. ISV and everything. Does the ISV "humm" and vibrate with the key in the "on" position?

Is your idle/full throttle switch pair (top rear and bottom of throttle body) in adjustment and working correctly? You can test it by checking for continuity at the 2-prong port behind the TB. There should be continuity with the throttle valve in the "rest" position. This tells the ECU to run its idle program.

It may be tough to do, but get the engine hot, and perform the procedure for setting the idle speed. You'll have to unplug the CTS harness connector (blue sensor located on upper coolant flange), and rev the engine over 2100rpm 3x. If your engine won't stay alive while you're trying to do this, unscrew (counterclockwise) the idle air bypass (front of TB) until you can get the idle to stabilize at 1000-1100rpm. Plug the CTS connector back in, and your idle should be stabilized at 850rpm. Once complete, rev engine past 2500rpm 4x. You may want a friend to help keep the engine alive while you're turning screws if you are having trouble doing it yourself.

It sure sounds like the previous owner went and fiddled with all sorts of adjustments before selling the car to you. Performing the above should get us a better idea of where your motor is at.

[Mongoxcore]

Thanks for the help, I'll definitely try out both things tomorrow. I've got the throttle body setup as correctly as I know how but didnt do that idle set procedure though.(I do get the idle 'Click' at closed throttle though I'm not sure if its actually doing anything, being nearly 23 years old.)

As for the PO.. I've spent so much time undoing the rigs and hack jobs I'm embarrassed to list it all

[Mongoxcore]

Had continuity at the port, but the idle set really didn't do anything for her. Had another person with me just to make sure it was done as smoothly as possible but no luck. Gonna see if I can get my hands on another Digi2 ecu.. Local yard I suppose. Should have em and will be cheap.

[orbanp]

First I would try to swap the ISV for a known working one.
My ISV likes to stuck if I do not drive the car for a while, behaves like yours, and then eventually gets unstuck.

Good luck, Peter

[VW_RAT_VW]

Delete the isv all together and see how to goes from there

[Mongoxcore]

First I would try to swap the ISV for a known working one.
My ISV likes to stuck if I do not drive the car for a while, behaves like yours, and then eventually gets unstuck.

Good luck, Peter

I'm 99% sure it works.. I get the humming and I've looked in on it working..

Delete the isv all together and see how to goes from there

Ya I'll give it a shot.. Im leaning towards there being something electrical, broken copper wire, or a bad sensor somewhere..

[spoon!]

Delete the isv all together and see how to goes from there

No.

[spoon!]

Get a Bentley, as it will tell you how to test everything.

[Mongoxcore]

Get a Bentley, as it will tell you how to test everything.

Haha trust me, I wouldn't come on here without already owning one
The delete would only be attempted as a lastlastlastwhynot resort. I'd much rather have everything hooked up the 'proper' way. It came off the assembly line working that way, why not restore it back to that.

[vinski203]

I'm wondering if you ever got this figured out. I'm having very simular symptoms and I just discovered my ISV doesn't work. I think I'm going to try to find one in a JY to see if it cures my problems. It's an awefully expensive part... being that in all my 30 years of driving I've never owned a car that had to use one of those just to run.

[Mongoxcore]

Well the isv would be one of the very first things to check. Im still messing with it. I put in a tt cam and new lifters, she finds idle quickly and holds it beautifully for about 5 seconds, then starts freaking out and will die unless I give her a bit of throttle.

[vinski203]

That's almost exactly what mine is doing. Except sometimes it doesn't even want to start now. That's something that recently just came up. And I've noticed it getting worse now that the weather is getting hotter.
I took my ISV out and applied power to it and it does nothing, so I'm pretty sure it's bad. Kinda hard to believe that's the only thing going on with mine though.
Here's something else it does... when I do get it started and its idling rough, after about 2 minutes of driving it's fine- runs normal and idles good.

[vinski203]

Here's something else I've noticed... if I remove the oil fill cap, the car stalls. Also never seen that in all my 30+ years working on cars. Is that normal for this engine design?

I may start another thread, but if you're reading this and have replaced your ISV, did you replace the rubber hoses it connects with too? I need to replace mine and can't find a source for new ones.