I have a 93 245 (LH 2.4) that idles rough when cold, almost dying and then surging up. It also misses at part throttle cruise, but not at WOT. The plugs burn bone-white and the car acts as if it has a vacuum leak. After it's warm it usually idles OK, but a bit low, but sometimes still won't idle. The ECU doesn't set any codes. I've checked every inch of every hose and have used soapy water and propane to try to hunt for leaks without success. I've also changed out or checked with a spare the following: O2 sensor, engine coolant sensor, plugs cap and rotor, fuel relay (and checked fuel pressure), throttle switch, idle air control valve, the one-way valve to the HVAC vacuum tank, and I cleaned the injectors and re-installed them with new seals. I've also cleaned all the contacts in the connectors and greased them with dielectric grease (except for O2 sensor), and checked all the engine grounds.

I have never encountered a problem like this that I couldn't trouble shoot in more years that I care to remember, and this is my last attempt to figure it out before I take it to a pro. Any advice is welcome. Thanks.