4K Pcv Valve, Pulling To Much Air At Idle

[rebuilder86]

I'm going to ask and answer my own question, and hope that someone with more knowledge can expand on my question and answer.

My 4k idles ok, but the mixture screw does need to be about 4 turns out rather than the 2.5 as recommended at stock.

There was no vacuum leak, but I today decided perhaps the PCV valve was dirty; allowing air through, not clogging it.

Incidentally, the PCV valve on it seems to be some sort of plastic knock off 'ONE SIZE FITS ALL' type.

I pull out the PCV valve from the rocker cover and at idle my finger is pulled to it like a freight train pulling a 100 carts of ore.

When I put my finger on it, it purrs like it should. So I'm going to assume this PCV valve is not appropriate.

 

I've taken it apart and it is functioning as it should, it has 2 springs, and the suction does pull the piston barrel thing back into the housing as far as it can. However it really leaks lilke a sieve when in this tightly closed position.

 

Anyone know of a part number or a picture of what the original looks like?

[rebuilder86]

Update,:

I now realise that the reason its sucking so hard is because when i put my finer over it, I'm in effect extending the vacuum to beyond the spring and plunger and this is allowing the plunger to open fully.

However, it still leaked too much air and affected the idle, especially when cold.

So, I cut up a little piece of plastic drilled a hole in it, and made a sealed seat for the sliding plunger to seat up against.Putting my finger on the end still makes it click open and suck, albeit with less of a click.

[altezzaclub]

I'm in effect extending the vacuum to beyond the spring and plunger and this is allowing the plunger to open fully.

 

Yep, that is why it sucked hard.

 

made a sealed seat for the sliding plunger to seat up against.

 

Clever! I didn't realise there were aftermarket plastic ones! Usually you can spray the hell out of it with brakeclean or carb cleaner to clean the seat out, but they might melt plastic.

[rebuilder86]

well see, this one is just shit, inside its just its metal on metal, the metal conical shaped plunger goes in and out against a metal washer, and that is the seat, in its most closed position, there is about a 0.05mm gap all around the face.

 

It looks exactly like this but straight and not 90 degrees.

http://contentinfo.autozone.com/znetcs/product-info/en/US/chl/PC285/image/3/

Its purring now. like a modern engine, no kicking or rocking around in the engine bay. Altho the mixture is set at 3 and a half turns still.

[LittleRedSpirit]

Mixtures and idle get wound up on dirty carbs. First thing id do is carby clean the hell out of it while using your hand to cover part of the carb throat and increase vacuum and rpm. Should create extra un natural suction and draw any grime out of the carby. Short of a strip and rebuild that should help. I've had 4k auto cars that wouldn't idle and then did the clean and found they had to be wound back into stock screw position as people had just kept winding up the idle to keep it from stalling over the years instead of servicing the carby.

[parrot]

They gunge up. If you have ever run an overflow bottle instead of the usual plumbing back into the intake so it gets burnt, you will see the oily water muck that it has to pass.

 

They are readily available online via the usual channels or likely your local aftermarket parts retailer. Otherwise give it a long soak in some serious solvent.

 

Edit: the metal ones that is.

Edited February 10, 2016 by parrot

[rebuilder86]

Little Red, i have rebuilt this carb 3 times now. Its clean as I can get it, every single orifice. The mixture needle is in tip top shape also, and so is the seat.

However, the inside surface of the little brass tube pressed into the casting that the fuel and bleed air goes down past the idle stop solenoid, is quite rough. Perhaps it is restricting the flow a bit.

I should emphasise, I only need the mixture out this many turns to make it idle when cold or hot. If I put it back to 2 turns it will still idle, but not until its nice and toasty. I'm in the philippines so installing the choke as a functioning component seems ridiculous. I have tried manually operating the manual choke to see if it helps, but it makes ZERO difference to the issue when cold.

Float level is perfect, when fuel bowl cover is opened, the fuel level is at the step just as the factory suggests, and this also gives the best idle for me incidentally. I seriously think my idle jet pickup orifice is too small. The orifice is so frikn small, I can only just see through it, but I can literally blow no air through it with my lungs.

I did try running it with the idle jet/pickup tube unscrewed and just sitting in place in its hole, and it idled amazing as it let more fuel through, but my brain told me to screw it back in to save fuel, after all it was designed by engineers.

I Just don't understand the point of having a jet up the top of this pickup tube, when that jets diameter is about 4 times bigger than the atomiser orifice at the bottom of the pickup tube. How is that a jet? its the opposite of a jet, its got less flow behind it to make any mixture accelerate through it, its decelerating through it. Doesn't make sense to me.

 

Parrot, My PCV gets full of oil after one day of hard driving. I can't see the oil causing any problems tho, not untill it starts to become dirty. Its just clean runny oil, if anythign it should help my cause by plugging the idle air leak the PCV valve creates by design.

Edited February 10, 2016 by rebuilder86

[parrot]

You shouldn't be getting clean oil out through your PCV.

 

There should be a deflector plate on the inside of the rocker cover to prevent oil being flung up from the rocker shaft and out through the PCV hole. If you can shine a light down the PCV hole and see the rockers, it's missing. All that should be coming out is scummy condensate.

[rebuilder86]

It is there, but it doesn't stop much oil. I may have exaggerated when I talked about how much oil there is.

None of the cars I have ever owned have had a flame arrestor plate / oil throw-up catcher plate thing that has actually worked.

I think the theory is borked. oil can exist as a vapour, and it is this vapour along with the carbon in it that causes sludge in the top of an engine (rocker cover) and therefore incidentally also in PCV valves.

As a liquid its not such a bad thing, its keeping the damn valve clean, so long as it is constantly getting a little bit and not too much.

Id like to know if anyone actually has a PCV valve in a 4k that actually stays clean after one hard drive.

Edited February 10, 2016 by rebuilder86