Hi 3rd Gens
While fitting a cold throttle body gasket to a friends '97 3L I noticed an excessively thick coating of oily grime from the throttle butterfly on - and it didn't even have EGR. I checked the PCV valve and found it stuck open! I subsequently checked another 2 cars and all had a similar problem To anybody trusting their repairers to do all the right checks - it dosn't always happen. Running an engine in this condition sucks excessive blow-by oil and lowers intake vacuum when it should be at its most efficient. To check - remove the valve and then shake it vigorously you should hear a distinct rattle sound from the spring inside, also if you blow into the smaller end it should not allow air to pass - blowing the other way should. To clean, put enough fuel into a 2L white container to soak the valve then agitate it until you notice small flakes of hardened oil deposits appearing. Add 50% volume of metholated spirits and repeat 3 times over the next hour until no further improvement and it passes the tests above. Now you might notice a "lighter" feel to the throttle on cruise :cool:

mine used to let alot of oil through, but now with my big shiney catch can its stop alot of it :cool:
my little valve thingo was blocked aswell wen i put on the catch can so a quick little clean and it was all good again

PCV valves don't work that way anymore.When they have full vacuum they still pass some gases and when vacuum drops the weight drops allowing mores gas to pass etc.,

Hi eagleaus
I was just reading the Gregory's service manual #272 P109 section on emission control and it confirms the operation as I described. The PCV valve opens fully on high vacuum but is designed to effectively close on large throttle openings where the flow of crankcase vapours may actually reverse, being drawn into the throttle body instead of the intake manifold.
In any event I also confirmed this myself when I did what I described in my thread.

Also you describe "..when vacuum drops the weight drops..." If you are referring to gravity the PCV valve weight cannot drop because the valve is actually on it's side, and this is one of the main problems with this design, and the reason why all the Magnas I checked were stuck open - regards, Barry

Any chance of a pic showing where this valve is located (for us dummies)?

The PCV in my car and all Magna's of the same age don't have a spring as you can use them as a rattle.Your right about the flow being reversed, thats why i stuck a one way air valve in the hose from the intake that i got off a old Sigma.

i think ive seen 2 that work propily in 12 years they all seem to suck a little at idle, all cars should have the throttle body cleaned and base idle reset at least every 40000km

so where is this thing? I can only find an EGR valve in the manual - is that it?

Hi Sarras
Sorry, don't have a pic - it's the small black plastic item fitted into the front engine cover on the driver's side (where the front 3 spark plugs are) and has a hose going to the intake. To remove just ease the valve from side to side as you pull it out of it's rubber mounting - best when the engine is warm :cool:

This it?

Thats the little fella

this is an extract from mitsu manual.

POSITIVE CRANKCASE VENTILATION SYSTEM
CHECK
1. Remove the ventilation hose from the positive crankcase
ventilation valve.
2. Remove the positive crankcase ventilation valve from
the rocker cover.
3. Reinstall the positive crankcase ventilation valve at the
ventilation hose.
4. Start the engine and run at idle.
5. Place a finger at the opening of the positive crankcase
ventilation valve and confirm that vacuum of the intake
manifold is felt.
NOTE
At this moment, the plunger in the positive crankcase
ventilation valve moves forward and backward.
6. If vacuum is not felt, clean the positive crankcase ventilation
valve or replace it.
7. Install the positive crankcase ventilation valve.
POSITIVE CRANKCASE VENTILATION (PCV)
VALVE CHECK
1. Insert a thin rod into the positive crankcase ventilation
valve from the side shown in the illustration (rocker cover
installation side), and move the rod back and forth to
confirm that the plunger moves.
2. If the plunger does not move, there is a clogging in the
positive crankcase ventilation valve. In this case, clean
or replace the valve.

Thats the little fella

Hmmm... well I just pulled mine and it did seem full of gunk and sluggish so I gave it yer treatment - thanks for the tip!

excuse my ignorance but what are the symptoms of a blocked pcv valve?

Hi SYNRGY
If the PCV was blocked closed, you could get poor engine response, idle roughness, possible oil seepage from engine covers etc. In the case of 3rd Gens I have checked the PCV was stuck in the open position, allowing excessive crankcase fumes to be sucked into the throttle body. This process is gradual and builds up over time. I would recommend that you should routinely clean the PCV at each oil change - the time spent would be well worth it! :cool:

Hi SYNRGY
If the PCV was blocked closed, you could get poor engine response, idle roughness, possible oil seepage from engine covers etc. In the case of 3rd Gens I have checked the PCV was stuck in the open position, allowing excessive crankcase fumes to be sucked into the throttle body. This process is gradual and builds up over time. I would recommend that you should routinely clean the PCV at each oil change - the time spent would be well worth it! :cool:and would this cause some smoke to blow out of the exhaust at full stick aswell?

One very important role of the valve is to prevent a backfire entering the crank case where this could cause a fairly impressive explosion. I once saw a Gemini with the PCV removed and a simple pipe installed where the top of the carb mounted to the air filter casing. The rocker cover parted with the engine.

Most cars have the PCV replaced at major service. You can clean it and yes it does have a spring in it and it will rattle when shaken, especially once it gets older.

Hi JO_KING
That seems quite likely to me but would also depend on other factors like how worn is the engine (K's travelled). However I'll let a qualified mechanic answer that one.
I would definitely clean it anyway though - it can only help :cool:

Thanks Barry

it probably doesnt help that the poor old 3.0 has done 310,000klms hey lol but the motor still runs strong and can keep up with a TL/TW aswell as still beat most 5.0ltrs stock for stock.
i cant complain about the mitsu motor at all a very strong part of the car same cant be said about the boxes lol.
at 310,000 kms i would be thinking its a case of valve stem seals and/or piston rings

when i first got my car the pcv valve was glogged so it was stuck closed. What happened in the short term was that the car would stall instantly, the RACV guys said to rev the car a little on start and then slowly let my foot off the pedal and the revs would come up.

Now its cleaned out a bit the car will start and idle properly. I dont think its properly fixed as i get the rattle but only when i shake it real hard, i think it should only require a gentle shake to make it rattle.