Everything was closed, lights and radio were off. No matter what I try I can't get the idle speed below 850.

By the way I forgot to mention that I removed the spark plugs today and found signs for the car running damn rich. The upper pulgs were black with a thick layer of carbon. The lower ones were completely brown. More like what I'd await to see at the upper plugs.

 

If you feel that dialing into a 750 rpm idle is compelling then disconnect the plug to the BAC and set idle lower than 750 such as 650-700 rpm and then turn the car off and replug the BAC and then start the car and let it find its idle and see if it can run at 750 rpm.

Since the upper plugs are trailing then you might want to replace those or just clean them off and see what good it does if any.

 

I allready cleaned them. No difference. I'm going to try the idle thing tomorrow again.
If one of the coils is damaged, which one would it be to cause those hesitations?

By the way I'm going to have a closer look at the groundings again tomorrow. Should I try to ground the air flow sensor directly at the connector maybe or would that be a bad idea?

 

I would go ahead and disconnect the trailing and see if it behaves the same exact way or not.

Depends on whether you're confident that the grounds are good as is. The ground wire at the AFM feeds 4 other sensors so if one is good then they "should" all be good. If you do add a ground to the sensor then ground the other end to the engine such as at the thermostat housing.

 

Going to disconnect the coil tomorrow then. Something is wrong with the grounding. I'm going to fix that, too. By the way: which sensor is the third? Pressure sensor, airflow sensor and which one else?

 

Actually, there are five others. TPS, Variable Resistor, Water Thermosensor, Atmospheric Pressure, and the Intake Air Temp in addition to the Boost Gauge. All fed by pins 2C, 3A and 2R.

 

I finally managed to find the reason for those high rpm hesitations. Sounds totally stupid but it was a broken rpm gauge. I changed it today because sometimes it got stuck and was beeping all the time then. With the new gauge electronic my hestations are gone, too. I still can't explain why but i think it was producing some weird fuel cuts somehow.

I only got one other problem now. I can't adjust the idle speed. I tried it today again with bridged initial set coupler and unplugged BAC. The engine was idling at 400 rpm and no matter what I tried I wasn't able to get it any higher. I also tried it with plugged in BAC but got the same results. What the hell could have happened here?

 

I'll guess one of the two wires in the BAC plug is pulled back within the plug and not making proper contact or you left the Initial Set Coupler jumper in place which minimizes the affect of the BAC when you elected to plug the BAC back in.

 

No no the engine was idling at 850 and I wanted to adjust it a bit so I grounded the initial set coupler. After doing that the idle speed immediately went down to 400 and I wasn't able to get it up to 750 by turning the idle adjust screw. In fact I wasn't even able to get it above 450 even when I turned the screw out nearly completely.
When I removed the bridge form the initial set coupler the idle went back to 850.

 

Have you involved the Variable Resistor in trying to set the idle?

 

One other thing would be if the removal of the Initial Set Coupler allows the idle to rise to 850 rpm from 400 rpm then try to adjust the rpm lower than 400 rpm so when the jumper wire is removed the idle only returns to 750 rpm. If you were to do this then the Idle Adjust Screw would be used to lower the idle speed and not increase it so it would be tightened as opposed to loosening it.