I have a DTC 55 code. The check engine light only comes on when at steady high speed driving 100km/hr(60mph). The error according to all data is Fuel Lean Monitor.
Is this an oxygen sensor issue or injector problem? The fuel pump was changed a year ago. I checked the spark plugs(bosch platinum +4) and they are all a white color, is this normal? The car is a 1995 Sunfire with the 2.2ohv engine.

poeple have problems with bosch plugs i've noticed try the delco ones or the denso ones and see if it changes

White = running hot you are either running the wrong heat range of spark plug or your injectors are not delivering enough fuel.You said your fuel pump was replaced so I would think it should not be a problem.If the car feels like it is making good power then your injectors are most likely ok. Replace your spark plugs with a set that are two heat ranges cooler than the ones you have. They should turn to a light brown color when the combustion temps are good .



Thats Him Officer The WICKED One.

I've changed plugs to NGK platinum, new plug wires, replaced the fuel filter and the o2 sensor. I still get the check engine light when cruising at speed but not when under heavy acceleration. I do have a very minor coolant leak from the head gasket, would this be the problem?

Also the GM coolant sealer pellets are they safe or will it plug the heater core? I'm trying to hold off a repair on a minor coolant leak from the head gasket on a '95 GM 2.2ohv.