horrible running 16V gti One for the Experts!

[the_GTI_new_guy]

1991 J 16V mk2. Had real trouble with my valver this morning. Started up normally, drove about 10 miles. Suddenly it felt low on power. When idleing after this, dropped to 700-800 revs and stays there (normally 1000 spot on) Engine shakes enough to feel in the steering wheel. When cold starting, , i accelerate and sounds really rough up to 300 revs when it gets fine. Last drive i did, diped the clutch, foot off accelerator and revs shot up from 2000 to rev limit and fell back to idle.

I had a go at changing the CO screw just incase it was out. When i touched the screw with my allen key, it droped idle dramatically. When i touched it for longer it stalled. I turned it ach way and did not see any difference. I been told revs should smoothly drop down to 1000 when clutch dipped but it falls fairly fast.

Only other info i cn give you is the idle valve buzzez but if i squeeze the air tube that goes to the valve for a while it makes no difference to the idle.

Anyone any ideas? Cant drive it like this, feels like a 1 litre 8V 

[jettaTx]

Sounds like a pipe off somewhere i had a similar thing happen a while ago. Check all the pipes are connected esp the idle stab valve,

[the_GTI_new_guy]

All pipes connected. Pipes on idle valve ok. I even cabletied the joins incase. Any oher ideas?

[murano3]

Yeh,

Two things, I had a similar problem which first showed it self as random reving .. i.e. I'd pull upto the lights and suddenly the rev's would increase to 2500 ... if I blipped the throttle it would eventually clear it .. well to fix that I fitted a new throttle sensor .. all seemed good for about 2 mins .. then it was like hitting a brick wall .. the car just wouldn't drive, idleing madly ... it would race between 700 and 1000 .. would fight back when you accelarated.

The fix .. I disconnected the sensor that sits below the piping into the airbox (look at the engine head on, look at the piping on the left and then feel down around it, the sensor is plugged in below and to the right, quite tricky to get to. This was recommended by a VW specialist. "Apparently" this sensor is unrequired on the 16v, however when it fails it causes allsorts of problems.

I've now been driving without it for miles and the car is fine.

One other little check though is to make sure there is no moisture in your distributor.