I Rebuilt the 4ZE1 engine in my 88 Trooper about 6000 miles ago, and i has had a weird "surging" problem since about 3000. Let me explain: when the engine is under stress at low RPM such as 2000 RPM going up a steep hill, the engine will surge like one or two of the cylinders are not firing. This also happens uder engine braking at low RPM. The lights also surge. I took it to a mechanic, and he said it might be the voltage regulator (btw, is this built into the alternator?) because the voltage varies about a volt. I will check the regulator probably today and post the results. Hopefully some of you have had ecperience with this? Oh, and when I blew a head gasket and pulled the head, two of the cyliners were black with what looked like fowling/carbon buildup.