I have a 2002 turbo charged Proton Perdana. If left to idle in drive for an extended period of time it will blow large quantities of blue smoke out the exhaust pipe. If you drop it into neutral when idling, no smoke of consequence is emitted.

I suspect that the problem is that when the car is in gear the intake manifold pressure is slightly higher and this causes whatever constitutes a positive crankcase ventilation valve to open. When the car is in neutral, the intake manifold pressure is slightly lower and the valve remains closed.

I have been unable to source a maintenance manual for the vehicle and because it is turbo charged, the plumbing associated with crankcase ventilation is not obvious (at least to me).

Can anyone explain how the crankcase ventilation system works on a 2002 Proton Perdana or direct me to where I can obtain a maintenance manual?

Here are some photos of the engine bay:

View from in Front of the Car

Close Up of Hoses Connected to Front Rocker Cover

View from the Right of the Car

  • In America, pcv valves are configured to feed combustion blowby gases from piston rings to feed back into the intake manifold for reburning with fresh fuel/air mixtures. Turbocharged engines may suffer coking, overheated turbo bearings not sufficiently cooled with recommended engine idling time after a hot drive. Coked bearings wear with excess oil ingested into the intake air system. Oil burns with blue exhaust. High mileage turbos with high oil consumption usually needs rebuilding to halt oil burning.
    – F Dryer
    Commented Dec 21, 2023 at 9:29
  • Welcome to Motor Vehicle Maintenance & Repair! Commented Dec 21, 2023 at 14:08
  • The oil consumption is between 1 and 2 litres per 5000km. I guess that's between 1 and 2 quarts per 3000 miles. At least some of it is leaking seals. Would you consider that to be high or low oil consumption?
    – Jonno
    Commented Dec 22, 2023 at 4:36
  • Thanks for the welcome.
    – Jonno
    Commented Dec 22, 2023 at 4:36
  • @Jonno - That is definitely high oil consumption, whether it's ingesting it or leaking it doesn't matter. Commented Dec 22, 2023 at 12:40

1 Answer 1


Fist off, thank you for bringing us your question! I'm going to break this down into two parts. The first part will deal with identifying the PCV system and how it works. The second will discuss the smoke and its diagnosis.

From the sound of it, you understand what a Positive Crankcase Ventilation system is for and, in general, how it works. I don't have a Perdana to look at in person, but this picture looks about right from my research: . Just in case, the PCV valve and visible system is circled(badly)

All PCV's have two things in common: they connect to the intake somewhere behind, as in closer to the engine, the throttle plate and they all connect to one of the valve covers or crank case. If you'd like to read a longer, more detailed explanation of how all this works on a boosted system, click here.

The shortest answer is this: When under boost, either the PCV is completely disabled or vented to the outside. The reason why is that forced aspiration can cause air to flow into the crankcase, creating its own host of problems. So either your system has a cut off, causing the PCV to close while the turbos are active or a bypass that leads to a vent. In the pictures of OEM engine on your vehicle that I've seen, it looks like it simply closes the PCV.

Now on the the smoke diagnosis! First off, I absolutely agree with starting at the PCV. You would be amazed at how many times I've had the honor of telling a customer that their engine is fine, they just need to replace this $15 part and the smoke will stop. If it is stuck open, I've seen an intake suck most of the oil out of a system in a very short period of time. And seeing the smoke increase at idle makes sense to me for this to be the issue. The smoke may be stopping when under load due to the bypass from the turbos.

It sounds like you already know this part, but I want to include it for completeness of my answer and in case someone else needs it. The easiest way to check to see if the PCV is your problem is to disconnect the hose from your PCV at one end or the other and stick your finger in it. If there is oil on your finger, it is time to replace your PCV. If not, then I would plug the end leading to the intake and run the car for a few minutes. Is it smoking now? If not, then your PCV is still the issue. If the smoke continues, you may need to run it for a few minutes to clear the oil out of the system.

Just a warning, if this has been happening for a long time, there could be oil built up in your intake.

Let us know if this solves your problem. Please feel free to follow up with any questions that you may have. If the issue turns out not to be PCV related, please close this post and open a new one.

[Edit] Okay, so I would really appreciate input from a more senior mechanic than myself. My theory is this: your system has two PCV/CCV systems. The reason why I believe this is that you have those two ports right night to each other. If one was a vent, it should be on the other end and it would lead to the intake before the throttle plate. Instead, one leads straight down and the other to the intake manifold somewhere. It's hard to tell because there's some sort of control valve around the intake and the hose. You can kinda see the hose loop over and then under again into the intake. Kinda. The other just disappears beneath the engine. You might look into finding the service information for it. I don't know where you are, but here you can go into an Autozone and ask them to look it up for you.

  • You sure that's part of the PCV system? Sure looks like something for an EGR to me. Plus, it doesn't appear to be connected to anything, either. Commented Dec 21, 2023 at 23:41
  • It leads straight from the valve cover to the throttle plate, so yes. In the non turbo versions, it doesn't have that bypass.
    – Geary
    Commented Dec 22, 2023 at 0:36
  • Thanks for the answer. Can you give me a day or so to take a photo of the engine? I think mine is laid out a bit differently. From memory, there's a hose from the front rocker cover going back towards the turbo charger, but no visible valve on the hose and it disappears under a whole lot of equipment on the right of the turbo charger (from the driver's point of view).
    – Jonno
    Commented Dec 22, 2023 at 4:44
  • Of course! We're operating on your time table.
    – Geary
    Commented Dec 22, 2023 at 17:05
  • I added some photos to the original question. If you can make any sense of the hoses it would be a great help.
    – Jonno
    Commented Dec 23, 2023 at 2:38

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