Two questions about PCV Valve and Gas Mileage

[TexasKiddo]

I have a 2002 Ford Explorer XLT, CEL has been on for a few months now, tryin to find out the problem but still cant pinpoint it, but anyway, I was told to change the PCV Valve that, that could be causing my CEL to come on, the guy at the parts store said, basically If I soak the PCV in gasoline and can hear the part inside rattle, then there is no reason to change the PCV valve. Is this true? Also was told that if the vehicle needs a tune up, the CEL will come on. Is this also true?

It seems that the vehicle has been using ALOT of gas here lately, go through a half a tank in no time, what can cause this? Im sure there are probably a million things that can cause this, but if someone can give me a little insight I would really appreciate it.

Thanks.

 

[E.B. Cornburner]

I've never heard of a PCV valve causing a severe enough problem to set a CEL.

Sounds like you may have a vacuum leak somewhere. Maybe the rubber hose that connects the PCV valve to the intake manifold...I've seen lots of Ford products that have a problem there.

A vacuum leak can also lead to poor MPG...The PCM is seeing an overly-lean condition, so it richens up the whole fuel curve to compensate for it.

Listen for any strange hissing noises while the engine is idling. With some patience, you should be able to pinpoint where it's coming from and correct it.

What code(s) are stored? Anything related to "fuel trim lean" or something like that would definitely point me towards looking for a vacuum leak.

 

[dogfriend]

the guy at the parts store said, basically If I soak the PCV in gasoline and can hear the part inside rattle, then there is no reason to change the PCV valve. Is this true?

The PCV valve is a check valve: it is supposed to flow vapor in one direction only. If it rattles and it flows in one direction(toward the intake manifold) and doesn't flow in the other direction it is working correctly.

Also was told that if the vehicle needs a tune up, the CEL will come on. Is this also true?

The CEL will come on when a DTC has been set. This usually means a malfunction of the emission control system. It is not meant to be an indicator that a tune up is necessary. The best thing to do is to find which code(s) have been set.

It seems that the vehicle has been using ALOT of gas here lately, go through a half a tank in no time, what can cause this? Im sure there are probably a million things that can cause this, but if someone can give me a little insight I would really appreciate it.

Thanks.

There are a lot of reasons why you might be using more gas than usual. Finding out what DTCs (codes) are set will help you narrow down the possibilities.

 

[aldive]

Sage advise.

 

[Alan]

Just to add a recent observation and post a question. I had a P0401 which indicated the DPFE needed to be replaced. I replaced it for $40 at Auto Zone (Ford wanted $102). Initial observations have showed my mileage has increased from 15 to 17 mpg non-highway, and that's being conservative. The challenge I'm facing is trying to understand how to use my OBD-2 scanner proactively. It captures real time data. Although I can see what the OS2 is doing, I don't understand it. I'm not sure what I should be comparing it to. How do I know if the information being posted is too high, too low, correct, or incorrect? I'm trying to research how to merge mechanical knowledge with technological tools. If the MIL is on, and you have a code, you have something to work with. What if you want to take the data being provided and use it to correct an emerging situation before the MIL activates? Any guidance would be appreciated.

 

[dogfriend]

. How do I know if the information being posted is too high, too low, correct, or incorrect?

In the Ford Powertrain Control/Emissions Diagnosis manual (PCED), there is a listing of typical PIDs (Parameter IDs) which you can read with a scan tool. The list is provided so that a tech can compare the reading on the scan tool with the "typical" reading that a "normal" vehicle should have.