Questions and Answers

Plymouth PCV Problem

Q. I have a 1992 Plymouth Acclaim 2.5 (Auto Trans., Throttle body fuel injection, A/C, PS, PB, cruise) with 268,000 miles on it (154,000 on current engine) in the past year or so I have noticed a dramatic increase in oil consumption (1 qt. /600mi). It still gets good fuel economy (27-28 hwy) and runs great. I have not noticed any smoke whatsoever coming from the tailpipe.

Now for the real meat: I have also noticed a lot of oil accumulation in the air cleaner assembly and filter. I have replaced the PCV valve and checked the hoses and connections all of which are OK. I read one of your recent answers to another question regarding a similar situation so I checked the vacuum flow and the PCV valve does suck air quite well. This engine has both input and output for the PCV system coming from the valve cover. When I remove both hose connections there is flow coming out of BOTH and when I reconnect the intake (PCV valve) side again there is still flow coming out of the air cleaner side (I guess after reading your description I expected to have a net inflow to the valve cover from the intake (air cleaner) side after reconnecting the PCV side. Where is all that flow coming from when I have both sides disconnected from the valve cover?

I am pretty sure the engine is not burning this oil as a matter of combustion. I had to replace a head gasket at about the 235,000 mile mark due to overheat because of a blown heater hose (those darn aluminum heads heat up fast!): The head checked out OK. During the head gasket change I checked the cylinder wall wear and there was hardly a ridge of any kind. I had to replace the catalytic converter a little later due to plugging.

Why the oil consumption? Can I stop it? What do you think? I appreciate your help!

A. To really check the system properly, you should use a vacuum gauge, but if you do not have one, a finger will do. With the manifold side hooked up, disconnect the air cleaner side and, with the engine running, place a finger on the inlet side of the valve cover. You should feel a slow, steady vacuum build up. After a minute or so it should be about the same as manifold vacuum so when you remove your finger it should suck in pretty good. if it does, the system is working properly.

The PCV doesn't allow full manifold vacuum to run through the crankcase, rather it allows a lower, more even flow. One thing I would check is the inlet pipe on the manifold that supplies the vacuum to the PCV and make sure it is not partially clogged. Gunk will build up in there and restrict the amount of vacuum the system gets. Also inside the valve cover where the PCV valve sits is a baffle to prevent oil from being sucked in. That may be clogged, either partially or completely.

Burning a quart of oil in a four cylinder engine with that kind of gas milage would not show any significant amount of smoke. It's possible that oil is being sucked up past the rings. This is a common side effect in a high milage engine and a new head gasket. You can look at the spark plugs and if the porcelain insulators have a black, sooty appearance, then the engine is burning oil. The normal color should be a light tan color.