Post idle adjustment experience / suggestions

[Nick]

Hi,

Was wondering if anyone could give advice or their experiences on the current behaviour of my 1986 non-turbo having adjusted the idle in various ways.  Sorry it\'s a bit long, but the fairly brief history is:

0) The car has been running fine.

1) a while ago the car was idling roughly for a short time after statup unless rev\'d, but idled at the correct speed.

2) a week or so ago the car would always idle at 1500, then climb to 2000, with the temp gauge going much higher than usual if standing still, and perhaps eventually drop to 1500 and maybe below again, but never idle at 750/850 as expected. Once moving the temp would drop to normal but rise very quickly if stopped for a minute or so.

I read up a bit, and with a friend we adjusted the TPS to sweep from 1K to 4.9 from previously 2.2K to 4.9K, and removed and cleaned the BAC valve. The BACV actually seemed ok and hadn\'t jammed.

We also adjusted a little screw on the top of the engine about 1 turn clockwise, and nearly fully in. The car would then idle at about 900 and be totally smooth.  However once cooled after a few hours it didn\'t start at all, but when totally cold and having backed off our changes a little, and drying the plugs, it started instantly but again had idle problems.

One symptom, mentioned elsewhere in the threads, is a hunting between 900/1000 and say 1300, as though the car wants to drop revs but is then running roughly and revs again to compensate, oscillating between the two states.

Now the idle isn\'t quite so bad, maybe, but a buzzer comes on. This may be from too little water in the radiator and so was topped up, and I don\'t know yet whether that\'s going to resolve the buzzer. There was no warning light, but the bulb may have blown. The oil level is fine.

From what I\'ve read, failing gaskets may be a possibility, and so wd40 sprayed around the hoses to see if the revs rise has been suggested to check for that -perhaps easier than listening for sucking noises.

One other perhaps not unrelated thing is that water vapour or something rises up from the air filter side of the engine, and seemingly below the filler cap region, for a short while after being turned off. This smells like coolant mixture but there\'s no obvious leaks and I can\'t pinpoint any source yet.

I have the feeling that tweaking things may just be masking the problem, and would appreciate any thoughts. Risking a trip to reading to be looked at properly may be necessary, but if there\'s more that could be done before that then I\'m keen to explore further.

All advice welcome.

Nick