Chevrolet Mystery

A couple years ago while maintaining the 94 Chevrolet Lumina Euro I bought a new PCV valve and installed it. My son then took the car to his summer job four hundred miles away. During this time he mentioned something about the car needing a lot of oil. The car had never burned oil, so this was unexpected. The last week of his job was at a camp his sister was attending. After the camp was over we planned to meet them at a family get togather a couple hundred miles from the camp. He needed a couple quarts of oil, and a change when he arrived at the camp. He had the oil changed, and it appeared to be fine when they arrived later at the family get-together. We drove home caravan style, checking oil and fluids at fuel stops. An hour from home the Chevy need more than two quarts of oil. After getting the car home, I noticed oil in the intake. In fact there was oil all the way out to the filter. Fearing the worst, I tore the top of the engine down removing the throttle valve, plenum, and intake manifold. I Checked and replaced gaskets, valve seals, etc., but found nothing particularly wrong other than problems I caused along the way – a car may run with a loose rocker arm, but not well, and your teen daughter will not appreciate the situation. Eventually, I got everything back right, and working properly, except oil still showed up in the intake. When I had disassembled the top of the engine, the intake was coated inside with oil, primarily around the number one and two ports. The local experts diagnoized this to mean a hole in a piston, or maybe a frozen ring, or cracked head. Don’t you just love how we experts go for the most difficult and expensive solutions every time? It was decided my daughter would drive the car to her high school, and I would rescue and repair it as necessary. The car ran generally well, except for difficulty starting, which still exists. While trying to imagine how to correctly diagnose and fix this problem, and having convinced myself that it could not be a piston or valve issue, I decided to go back and work through the trouble from beginning to end. I checked the time line of the problem. Noticing the problem appeared after the PCV was changed, I pulled it out and inspected it. It appeared to be fine. Out of courisity I decided to compare it to an older valve which I had previously removed. I noticed the air passage in the new valve was much larger than the old valve. Replacing the Positive Crankcase Ventilation Valve ended that particular oil in the intake problem. The PCV valve had a manufacturing defect which allowed oil vapor from the engine to be pulled through into the intake where it condensed back to liquid form on the surface of the cooler plenum, and then flowed out through the throttle valve into the intake and filter plumbing. I was surprised at how much oil could disappear this way. Two quarts in two hours is more than a bit. If I had not watched it happen, I doubt that I would believe it could turn out this way. The various projects involved in diagnosing and fixing this three dollar problem took several hours, on several saturdays over several months. I suppose the moral of this story is always check the new part against the old to make sure it’s specifications are exactly the same. Many good part shops have experienced people who automatically do this if you have the old part. Many don’t. So even if the part is top of the line you need to check it – cause what you don’t know can hurt you.


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