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Rough start only when cold, engine rpm races up and down and will stall ; not when driving

My boyfriend is a mechanic for the forest service so the last thing he wants to do is fix my car. The engine code that is being thrown off is that there is a lean mixture problem, O2 sensors problem.

He cleaned the throttle body, replace air fileter, pcv, fuel filter and it was recently tuned.

So, he replaced the upstream oxygen sensors, which made no difference. He has considered replacing: electronic idle air control (speed control), temperature sensor, the other two downstream O2 sensors, too time consuming maybe…the gaskets on manifold (could be an air leak) since this is outside the computer. All of this throwing parts at a 1998 ford explorer is money…since only one income, we would like some suggestions from anyone with knowledge fo this engine 4.0l SOHC.

Thanks for your assistance.



oh, yeah…he brought home a new idle air control valve but was hesitant to install it since u know u cannot return opened parts, also wire had to be fitted since not Ford part