Hello all,

I've got a very nice 1985 245 turbo, has a rough idle when running OK - at times the idle will just plunge below 1000 and it will stall. When it is idling the exhaust is smelly so I assume it is running rich. I've managed to get the car to run without stalling by adjusting the main throttle stop screw. However this leads to the occasional situation (usually in hot weather) where the idle is unnecessarily high.

I bought this car about five years ago and it's remained drivable (in fact I drove it to the East coast from Portland, OR), and always figured some day I'd replace the idle air motor and that might fix it. Since the idle air motor is quite difficult to get at, this never made it to the top of my list.

I recently had the idle air motor replaced and it still does this. It runs rough down below around 1500 rpm, and bucks when driving in gear at low engine speed. Given the smelly exhaust and the rather irregular miss, I thought it might be the O2 sensor, so I took a look and - the port on the manifold is just plugged with a bolt. The green wire from the firewall is just hanging there disconnected.

One other piece of info, I recently replaced the cap, rotor, plug wires and plugs. It had been running iridium plugs but I installed the original spec Volvo plugs. With these plugs it seems to be running even worse.

I suppose the CIS system might be working fine but the engine is just unable to run properly at the low RPMs controlled by this system, due to improper mixture. Any thoughts on how to go about troubleshooting this would be appreciated.