PCV Valve. Cure for Misfire ?

[Toplesscouple]

Ever since we've owned the car, 10k miles ago, we've had an issue with P301, cylinder 1 misfire. Tried new air filter, MAF clean, new plugs, swapping coils and injectors all to no long term avail. Only time it has been off for any length of time was a trip to warmer climates. The misfire was only noticeable on tickover although the acceleration was not always smooth with a 'stumble' at each gear change. It struggled to get through the emissions test at the recent MOT. The garage reckoned to have cured he misfire by fitting a new coil pack to cylinder 4 and replacing the 2 new o2 senors with the old ones   s:? :? s:?  The CEL light came on before I even left their carpark   s:x :x s:x  

So having read various posts about the PCV valve mainly on Corolla based sites and on here, I opted to buy a new one. It seems that it is recommended to change them around 30k miles. My local Toyota dealer had difficulty in locating it on their parts system, but after various emails to them they finally found it as an Air Valve. Drove over to them last weekend and fitted it in their carpark. 5 minute job. It evens comes with a sealant applied to the threads. I was initially disappointed as the old valve did rattle, which is supposedly indication of a healthy part in this case, but was pleasantly surprised when the engine immediately idled smoothly. Since then the car has done several cycles including starts from freezing cold when the CEL would flash furiously before settling back to  the constant glow. The acceleration is smooth now with a fluid upshift and it feels more tractable. Maybe this may be the cause of some other folks running issues too. Part no is 12204-22051 (Valve Sub-Assy) and cost just £23.61.

Valve location here

[Anonymous]

Thanks for the part no,just ordered one to be on the safe side.   s:D s:D

[AmeR]

Think I'll be opening the wallet next week and trying this too!!! For the cost it is worth a try!

[Chris H]

Not like you to be spending on the "2" AmeR,  s:) s:)  ......not touching mine,after the
pre-cat removal yesterday ,its running like a dream,not that it wasn't before,but it seems
different without the pre-cats.....  s:) s:)

[dcod]

Changing my PCV valve cured chronic oil consumption. I currently have an oil leak from an oil seal which I believed was caused by the valve.

When I went to Toyota to buy a new valve they'd never heard of it   s:shock: :shock: s:shock:   I explained what and where it was and that I had a 2zz-ge engine ... needless to say they'd never heard of that either   s:shock: :shock: s:shock:  I explained the engine was from a Celica GTS and was in my MR2 ... they said that would make it more difficult to find the part   s:shock: :shock: s:shock:   ... f*ckwits.

I did some investigation into the valve and the PCV (Positive Crankcase Ventilation) system :

 l viewtopic.php?f=11&t=35469 l

[Al Beback]

Used this info to go from 2 litres of oil in 800 miles to no oil use in 500 so far. My PCV valve rattled when i shook it but i soaked it in WD40 and flushed it through a few times. After this it not only rattled but made a sliding noise, like a toy tube thing my kids used to have. After this I lubed it refitted it and my revs go straight to idle when stopping instead of searching.

[Smeggers]

I had a similar issue some time ago. After suffering with misfires and replacing the ISCV, i noticed that there was quite a lot of oil coming from the PCV hose. Thought no more of it for a while, unfortunately the oil contaminated the O2 sensor and caused the engine to run very lean, burning out the CAT before i noticed (no eggy smell from cat for a while). Looking at a few threads and investigating what the PCV does lead me to replace the valve which, despite sounding ok, was passing quite a bit of oil through the engine.

Lesson learnt. Change the PCV every couple of years.  s:( s:(

[ilovejapcrap]

Another thread revival,

Could you block the hose to see what this does

[Carolyn]

Yes.

[shnazzle]

Did this today on Helen's car. It did nothing....
Add it to the list.

[wotugonado]

Did this today on Helen's car. It did nothing....
Add it to the list.

Where did you buy it from ?

[shnazzle]

I haven't yet. I just let the engine run for a while and then clamped the pcv hose. Did nowt.

[wotugonado]

Ah ok.

[Carolyn]

I haven't yet. I just let the engine run for a while and then clamped the pcv hose. Did nowt.

It should do nowt - unless you PCV is wide open, in which case the engine will run better.

[shnazzle]

So what would be the point if it does absolutely nothing when you clamp it?
I must have misread.

[Carolyn]

Try pulling the hose off the valve and see what it does.  It should only allow a very small flow when the pressure differential overcomes the spring inside it. If it's stuck wide open it will mess with the running of the engine.

[jonbill]

It should die if you pull the hose off, right? I'm sure thats what mine does....

[Carolyn]

Indeed.  Big hole in the inlet manifold is what you get.

[shnazzle]

It does that. I must have confused clamping the hose with pulling  it off.

[ptennisnet]

It's also worth checking the hose.  Mine had a little split which was causing a leak downstream of the PCV and caused bad running.  I bodged a repair with an elbow hose connector and a new bit of hose, which has fixed the issue.  It looked too hard to replace with new as the other end of the hose was right around the back of the engine.

[shnazzle]

I figure might as well buy two for both our 2s as a matter of maintenance really. Both 12 years old so... Might as well.

[wotugonado]

Fitted mine and concur with op,  I had a slight hunting for idle when coming off the pedal and  occasionally a slight hesitation on gear change. Not anymore.......

I did a quick comparison of new and old valve, I did the rattle test which showed no difference, but if you turned them so the hose connection end was pointing upwards the metal plate inside that closes it shut was closed tight on the new valve but sagging open by about 2mm on the old one, so I presume the spring has failed.

[Carolyn]

You hit the nail on the head.  It's all about the spring pressure.  It might 'seem good' but the springs just get tired after a while.

[wotugonado]

Yeah it was sagging by a fair bit, I was amazed that such a simple cheap part made the difference that it has

[Justin.D]

So what does the PCV do? I've googled and got a load of confusing and conflicting answers.

How would I know if mine wasn't working properly? Will pulling off the pipe tell me straight away if it was needed to be replaced? It seems like a cheap part to replace so may just buy one anyway