I have a '91 300TE that idles around 1000 when you start it, then increases to around 14-1800 once warm.

Background (sorry it's long, but it's all inter-related):

I had a bad idler buffer and when I fixed this and put a new belt on it. About a month later, all the dash lights came on. It wasn't charging, only 12v at the battery. The belt was too loose. I tightened it, and it worked for about 2 days. But I guess it strained the alternater or something because voltage at the battery dropped to 12.5v. A new alternator tested fine when I first put it in (14v), but after a few days all my bulbs started burning out. I rechecked the voltage and it was 18v at the battery! Luckily while trying to diagnose the earlier problem I bought a spare regulator. I slapped this on and now the charging system works fine (and I was able to get my money back in the regulator instead of returning the alternator). However, I'm not sure how much damage was caused by driving around for a few days with 18v through the system.

What I've done:

I had a spare OVP relay I bought because it would die immediately after started the car when cold (except, strangely, sometimes when it was well below freezing out). This didn't help my cold start problem, so I kept it as a spare. Swapping it out doesn't have any effect. When I disconnect the idle air control valve, it seems to run fine. It idles normally. It doesn't start quite as easily, but other then that seems to run fine (I haven't taken it out of the driveway like this yet). If I plug it back in after starting, the idle jumps. After reading the engine diagnosis article on this site, I tried to test the dwell setting, but I couldn't get a reading. Not sure if I hooked it up wrong or if my meter is fried. Also, I was getting very little current draw (.13ma), that didn't seem to change.

So two questions: Does this sound like a bad idle air control valve, or a bad controler? Is there any harm in driving around with my idle air control valve disconnected?

Thanks,

Dave Sawyer
'91 300TE
'83 300D backup