RE: 86 CGT rough at low rpm

[Simon Allcorn <simon.allcorn@cartesian.co.uk>]

Sounds very similar to the problem I am currently having.

First off there a pipe from the rocker cover that goes to just above the 
air filter / just below the metering unit - mine was softer than  butter 
and had several holes in it and was 'crazy paving' cracked all the way 
down.

Second off I suspect that my auxiliary air valve (also called the ISV (I 
think - anyone care to correct ?) is stuck shut. I think this is then 
causing the engine to not have enough air so it gets extra air from the 
next easiest source - the pipe that was broken (btw there was also quite a 
bit of oil sucked in via this pipe). I should be checking the ISV this 
weekend so I'll keep the list posted.

Anyway if I'm correct about the ISV (I suspected for a long time the cold 
start valve (extra fuel valve) but I've connected the electrical supply for 
it to a light in the cabin and it's activity doesn't fix the symptoms) then 
if you get your car warm (warm as in the temp. gauge has been stable , i.e 
about 1/2 way for AT LEAST 10 minutes of driving) then the engine should 
show no hesitation at all.

Also you can check the ISV easily (There's a pipe about 1/3 - 1/4 inch in 
dia from the inlet manifold (next to the  supply for the brake booster - 
!turbo uk only I think) which goes into the ISV and then the pipe comes out 
and connect the upstream side of the throttle butter flies (don't you just 
love having 2!!). Anyway start the car when it's cold and pinch this pipe 
hard and the engine should stumble - if it doesn't then the ISV could be 
stuck shut. Then when the car is hot do the same thing but this time there 
should be no change in the engine tick over - if there is then the ISV 
could be stuck open.

Also make sure there are no vacuum leaks in any pipes ! (arse I know but so 
is no power at 2k!)


hope this helps.


Simon


87 coupe Quattro, no power at 2k when cold