excessive - Smoking and oil consumption -PCV
03-17-15, 09:47 AM
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excessive - Smoking and oil consumption -PCV
So my Lexus LS400 98 had the vacuum pipe to the PCV valve blocked off when I purchased it, and the PCV was left venting to atmosphere. Ran brilliantly until I noticed it, and ever since i reconnected it, it smoked heavily on start up and under load.... weather hot or cold.
So I purchased a new PCV valve from main dealer........and it did exactly the same thing!!!! Smoking and consuming oil into the intake.
I noticed that when I looked into the intake manifold through the throttle body that oil was pooling at the back....... but when I blanked off the breather to the PCV, the oil disappeared and the intake manifold was clean! and it didn't smoke anymore.... it ran perfectly ..
I am absolutely stumped at what can be caused this excessive blow by from the PCV valve.
Thats 2 PCV valves I have tried now, one brand new from main dealer, and they both have not stopped the smoking of oil. I am tempted to leave the PCV disconnected from the intake manifold as that has cured the smoking and oil pooling into the intake manifold.
Any thoughts or advice???? Thanks.
So I purchased a new PCV valve from main dealer........and it did exactly the same thing!!!! Smoking and consuming oil into the intake.
I noticed that when I looked into the intake manifold through the throttle body that oil was pooling at the back....... but when I blanked off the breather to the PCV, the oil disappeared and the intake manifold was clean! and it didn't smoke anymore.... it ran perfectly ..
I am absolutely stumped at what can be caused this excessive blow by from the PCV valve.
Thats 2 PCV valves I have tried now, one brand new from main dealer, and they both have not stopped the smoking of oil. I am tempted to leave the PCV disconnected from the intake manifold as that has cured the smoking and oil pooling into the intake manifold.
Any thoughts or advice???? Thanks.
Last edited by RA40; 03-17-15 at 09:50 AM. Reason: descriptive title
03-17-15, 11:45 AM
#2
Javeiro,
Sorry you still have the problem. I know it can be frustrating not being able to figure it out.
Not that I could help that much, but thought about putting an inline filter on the hose... maybe one of the clear fuel filter types that might help you see the issue.
Then found this link that had some informative information and a similar filter idea, but used an oil separator from home depot.
You could go back to the old arrangement from when you purchased it.. that's about how cars used to work as long as it vented somewhere, but know you'd rather have it working right.
http://www.stangnet.com/mustang-foru...-valve.637524/
Sorry you still have the problem. I know it can be frustrating not being able to figure it out.
Not that I could help that much, but thought about putting an inline filter on the hose... maybe one of the clear fuel filter types that might help you see the issue.
Then found this link that had some informative information and a similar filter idea, but used an oil separator from home depot.
You could go back to the old arrangement from when you purchased it.. that's about how cars used to work as long as it vented somewhere, but know you'd rather have it working right.
http://www.stangnet.com/mustang-foru...-valve.637524/
03-17-15, 12:14 PM
#3
and... found this that might be helpful also...
If the PCV valve gets plugged, here's what happens, roughly in order:
1 Excess crankcase pressure begins to back up the engine's breather tube, into the intake air tube upstream of the throttle body
2 Engine management system senses absence of air from plugged PCV valve, and adjusts fuel mixture accordingly. Engine makes slightly less power.
3 Oil begins to be pumped into the air intake tube through the breather hose, upstream of the throttle plate.
4 Oil runs down the intake tube into the throttle body.
5 Oil sludges up the throttle body and throttle plate. Gas pedal starts to get sticky. Airflow reduced. Engine management adjusts mixture again. More power loss, possible poor driveability.
6 Idle Air Control (IAC or EACV) valve gets contaminated and begins to stick.
7 IAC cannot adjust idle air mixture to compensate for plugged PCV valve. Idle drops, may become erratic as throttle plate cannot close completely.
8 Oil drips into intake manifold runners. Blue smoke seen out of tailpipe.
9 Breather tube begins to get constricted from oil contamination and airflow is reduced. Crankcase pressure mounts dramatically.
10 Oil pushed past valve guide oil seals. More blue smoke.
11 Dripping on driveway as oil is pushed past seals.
The above is the scenario for a modern car with a feedback engine management system, in other words, one with an oxygen sensor. Older cars without engine management systems were unable to compensate for plugged PCV valves, and the power loss, fuel mileage loss, rough running issues were FAR worse. A PCV valve that was stuck open could even result in a refusal to idle at all.
The function of a PCV valve is to control the flow of crankcase gases. Start your engine, then remove the oil filler cap (watch your clothes; you might get some oil splatters). Place your hand just above the opening. Feel the strong jet of air? That's "blowby", combustion gases that squirt past the piston rings into the crankcase below the pistons. Even new engines in good condition generate lots of blowby (but it's still a small
fraction of what passes through the throttle body).That jet of air has to be vented somewhere, otherwise it will quickly build up pressure inside the engine, and cause those aforementioned very bad things to happen. If the PCV valve gets plugged, blowby pressure has no proper place to go.
The primary reason for plugged PCV valves is neglected oil changes, which causes sludge. Secondarily, it also happens to engines that are primarily used for short trips, where moisture, fuel, and acids build up in the oil, emulsifying it into sludge, which is related to the neglect thing mentioned earlier. 3 months between changes might be too long depending on how you drive.
Also, an engine with worn compression rings will have massive amounts of blowby, which will overwhelm the PCV valve's ability to pass air and cause the excess vapors (and oil) to be pumped into the intake before the throttle plate.
Since the air inside the crankcase also contains contaminants like unburned fuel, water, acids and other things that your engine and its oil do not like, venting the excess pressure also helps to vent those contaminants out of the engine before they settle into the oil in the first place, so your oil stays a bit cleaner longer.
If the PCV valve gets plugged, here's what happens, roughly in order:
1 Excess crankcase pressure begins to back up the engine's breather tube, into the intake air tube upstream of the throttle body
2 Engine management system senses absence of air from plugged PCV valve, and adjusts fuel mixture accordingly. Engine makes slightly less power.
3 Oil begins to be pumped into the air intake tube through the breather hose, upstream of the throttle plate.
4 Oil runs down the intake tube into the throttle body.
5 Oil sludges up the throttle body and throttle plate. Gas pedal starts to get sticky. Airflow reduced. Engine management adjusts mixture again. More power loss, possible poor driveability.
6 Idle Air Control (IAC or EACV) valve gets contaminated and begins to stick.
7 IAC cannot adjust idle air mixture to compensate for plugged PCV valve. Idle drops, may become erratic as throttle plate cannot close completely.
8 Oil drips into intake manifold runners. Blue smoke seen out of tailpipe.
9 Breather tube begins to get constricted from oil contamination and airflow is reduced. Crankcase pressure mounts dramatically.
10 Oil pushed past valve guide oil seals. More blue smoke.
11 Dripping on driveway as oil is pushed past seals.
The above is the scenario for a modern car with a feedback engine management system, in other words, one with an oxygen sensor. Older cars without engine management systems were unable to compensate for plugged PCV valves, and the power loss, fuel mileage loss, rough running issues were FAR worse. A PCV valve that was stuck open could even result in a refusal to idle at all.
The function of a PCV valve is to control the flow of crankcase gases. Start your engine, then remove the oil filler cap (watch your clothes; you might get some oil splatters). Place your hand just above the opening. Feel the strong jet of air? That's "blowby", combustion gases that squirt past the piston rings into the crankcase below the pistons. Even new engines in good condition generate lots of blowby (but it's still a small
fraction of what passes through the throttle body).That jet of air has to be vented somewhere, otherwise it will quickly build up pressure inside the engine, and cause those aforementioned very bad things to happen. If the PCV valve gets plugged, blowby pressure has no proper place to go.
The primary reason for plugged PCV valves is neglected oil changes, which causes sludge. Secondarily, it also happens to engines that are primarily used for short trips, where moisture, fuel, and acids build up in the oil, emulsifying it into sludge, which is related to the neglect thing mentioned earlier. 3 months between changes might be too long depending on how you drive.
Also, an engine with worn compression rings will have massive amounts of blowby, which will overwhelm the PCV valve's ability to pass air and cause the excess vapors (and oil) to be pumped into the intake before the throttle plate.
Since the air inside the crankcase also contains contaminants like unburned fuel, water, acids and other things that your engine and its oil do not like, venting the excess pressure also helps to vent those contaminants out of the engine before they settle into the oil in the first place, so your oil stays a bit cleaner longer.
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03-17-15, 01:15 PM
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Well legender many thanks for your thorough reply, it is much appreciated!
I will have a read of that article and keep having a read. I did initially think that the symptoms were because of a bad blocked PCV, but even with the new one it smoked badly and burnt oil.......
Idle and performance is fine , very strange indeed. I will do a full service this weekend, oil and filter. I plan on using Petronas 5W30 fully synthetic, and a genuine Toyota oil filter.
Once again thanks for the reply
I will have a read of that article and keep having a read. I did initially think that the symptoms were because of a bad blocked PCV, but even with the new one it smoked badly and burnt oil.......
Idle and performance is fine , very strange indeed. I will do a full service this weekend, oil and filter. I plan on using Petronas 5W30 fully synthetic, and a genuine Toyota oil filter.
Once again thanks for the reply
08-12-17, 05:16 AM
#5
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PCV Valve Clogged
The issue being discussed here is not the PCV Valve itself, but the area where the PCV Valve is plugged into on the valve cover. There is a baffle in the valve cover where the PCV pluggs into and when an engine sludges up, that area gets sludge in it. The only way I have found so far to clear that area is to take the valve cover off and clean it good. This includes taking off the throttle body and intake to get access to the valve cover, but I have not been able to clear the baffle without taking off the valve cover itself and beleive me I have tried.
If anyone knows how to clear that baffle without taking off the valve cover please post. I have not fixed mine yet (still bypassing the PCV valve at this point).
If anyone knows how to clear that baffle without taking off the valve cover please post. I have not fixed mine yet (still bypassing the PCV valve at this point).
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UNCNOR (08-13-17)
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