PCV VALVE... Really?

[roadnsky]

Ok, clear the decks, here we go...

A week ago it was time for my annual carb cleaning.
After doing the maintenance, and while doing a test run, I felt I was running a bit too rich.
(I've actually felt this way for quite a while)
So, last Sunday I fiddled around with the Idle Mixture to lean it out.
But after getting to where it would just stumble and die at idle
and then adjusting a 1/8 - 1/4 turn back to rich, I felt it was still running rich.
I just couldn't find a sweet spot.
A NOTE HERE... my A4 runs great otherwise.
I just KNOW it's running too rich.
The up side to being a bit rich is that it starts the instant you push the ignition no matter how cold. But...

So, during some down time at work I spent some time researching on the MMI site about carb adjustment, rich running, poor idle, etc.
A lot of what I read and especially some of the recent discussions about PCV valves and blow-by got me to thinking.

So, this weekend, I first tore the carb down again to make sure it was clean and I put in new plugs.
(The current set were distinctly sooty)
Then I took off the Indigo PCV kit and put the stock "Slash Tube" back in and set about to re-adjusted idle AND timing.
Guess what?
I was able to lean the mixture AND maintain an excellent idle at 700RPM.
It wasn't as rich. It didn't smell or seem to be running too rich anymore. YES!!

A moment here about WHY I have the PCV kit in the first place...
When I first got this boat, I knew absolutely nothing about the A4
BUT I wanted to learn.
The engine was in decent shape but it needed some attention.
While researching sites and before I discovered the value of this site, I ran across Tom's Indigo site.
At the time, and given my very limited knowledge, the PCV made some sense.
AND I knew I had some fuel/carb issues, so I thought "what the heck?"
I ordered it and it was one of the very first "improvements" I made to the A4.

Now, knowing that I don't have a blow-by issue to deal with,
I've doubted my initial choice to install it for some time.
My compression numbers are:
#1 - 118 / #2 - 114 / #3 - 116 / #4 - 118

Anyway, I thought it was time for the group to explore and discuss the "blow by" vs PCV Valve issue. Really.
(I know, Neil is shaking here with anticipation)
Ok guys, keep it clean and let the fur fly...

[Mo]

Never used a PVC anyway. What type plugs did you put in there Jerry. Seems they might have been sooted up anyway with the carb running on the rich side.

[roadnsky]

...What type plugs did you put in there Jerry?

I use the AUTOLITE 437’s for a "hotter" plug. Gaped wider to .038

[romantic comedy]

How far off was the timing?

[roadnsky]

How far off was the timing?

It wasn't. Just re-did it to be sure it wasn't a contributor.

[ndutton]

Ooh baby, Christmas comes early

[Blazing Saddles] 'Scuse me while I whip this out



We'll see where the discussion goes but for starters it seems we're interested in exploring everything BUT the PCV. Maybe it's good to eliminate all the distractions before getting into it.

[sastanley]

Oh boy..here we go.

So, Jerry...when are you thinking about winterizing your engine?

(I have nothing of value to contribute at this time.)

[roadnsky]

Oh boy..here we go.
So, Jerry...when are you thinking about winterizing your engine?

Winterizing? What's that??!
Actually... to rub it in your nose...
Expecting 15K breezes with 60°+ temps this weekend.
(I'll take some sailing pics for you)

[joe_db]

I have tried squeezing off my PCV valve and it makes a very minor difference in the idle. YMMV.

[ndutton]

You're correct Joe. That's because the PCV valve is essentially closed at idle.

[roadnsky]

I have tried squeezing off my PCV valve and it makes a very minor difference in the idle. YMMV.

Try this...

You're approaching the slip with a 15-20K breeze on your tail.
You shift into reverse and hi-rev a few times to feather it to a stop in the center of the slip.
With my PCV installed, I looked soooo cool coming to a perfect landing...
... except for the blue smoke cloud behind me.

That was one of the classic symptoms of running too rich.

[Ball Racing]

You're correct Joe. That's because the PCV valve is essentially closed at idle.

Any other place than idle and you are losing vacuum in the manifold, so are we saying the pcv is not a major vacuum leak at idle?
This is opposite of I what I have noticed with them in the car world.

No matter what your views on a PCV I can't figure either, how a "vacuum leak"
made this carb in question run richer............

[Ajax]

If the purpose of the PCV upgrade is to correct smoke exiting the oil breather caused by blow-by, and you do NOT have blow-by, then I don't understand why one would install this modification.

My compression numbers are 100, 98, 102, 100, and I do have some blow-by and a smokey cabin if I really load up the engine, so I will probably install the kit.

[toddster]

Hmm... I'll just lurk and try to learn something here.

I've been thinking about the PCV mod because currently the cabin fills with fumes and the CO monitor is pegged whenever I motor for any distance. Although I have been running with the engine cover off for a re-build.

[joe_db]

Blue smoke is burned OIL.
Black smoke is running too rich.
So far my new engine does neither

Try this...

You're approaching the slip with a 15-20K breeze on your tail.
You shift into reverse and hi-rev a few times to feather it to a stop in the center of the slip.
With my PCV installed, I looked soooo cool coming to a perfect landing...
... except for the blue smoke cloud behind me.

That was one of the classic symptoms of running too rich.