"Your car is toast" ...PCV pipe/scored cylinders saga
06-14-2021, 05:21 PM
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"Your car is toast" ...PCV pipe/scored cylinders saga
Car is a 2006 S - just over 200,000 klms (or roughly 125,000 miles)
A lil' background...
- About a year ago, I started getting the "knock noise" from the engine - then my flex pipes went out (creating a loud exhaust noise, so it was hard to hear the "knock")
- After pipes replaced, knock was still there. Seemed to be the symptom of scored cylinders. Started planning on perhaps a rebuild when the car finally gives up. Added oil stabilizer/valve cleaner for the hell of it.
- Fast forward to this summer - knock still there, but sometimes is overridden by what seems to be a tapping valve or injector noise (this seems to come and go).
Car starter finally gives out (was getting bad starts for a while before starter went) - intake removed (replaced starter, water pump, thermostat, seals, etc). Had them take a look at the top of the vales while in there to see how bad they were gummed up (was going to get them to clean them hoping it would solve valve tick). They report back the valves are as clean as a whistle. Also, car hasn't been burning any oil since last summer.....
Get car back and expect a nice smooth start due to new starter, but am still getting random rough starts - just has more "power" behind them due to new starter (Bosch re-manufacture) - see thread about this here.....https://rennlist.com/forums/cayenne-...l#post17491586
Way better than before though, but not what I expected with new starter. NOTE - after getting car back from shop, they mentioned there was a "broken hose" that need to be replaced - said they taped it up for now until I get new hose. Said it was an "air hose", so I assumed it had something to do with the air pumps they remove for intake removal. Figured I'd get the new hose down the road.
Couple weeks later I start getting a dip in idle/shudder at stop lights/as rpm drops. Oh oh - engine finally starting to go? Did some searching and dipping idle could be motor mounts - figured I'd get them replaced if I pull the bottom of engine out for repair.
Rough starts seem to be getting worse. Usually won't start on first turn of key; have to turn key all the way back, remove, re-insert and try again. Weird noises from starter. Then it starts turning over and turning over and turning over till it finally starts. I now get my first "crankshaft position sensor" warning. Car seems to run fine (minus the slight dip in idle), but starting is a chore. Randomly getting "System fault" (too much air) warnings also. Also. whenever I cleared the codes for crank sensor/system, the car would run worse - you could literally feel it go from a bad idle to a worse idle after clearing codes. Also noticed car was now puffing out white smoke on start up/getting hard on the throttle. Not looking good for the engine/scored cylinders.
One night, after another bad start, the car starts running really bad - getting misfire, system fault and crankshaft sensor warnings. Look up crankshaft sensor symptoms and poor running is one of the symptoms (also noticed mention of a "PCV hose" in doing my searches related to the crank sensor). The next night, the car won't even drive more than 2 minutes without stalling (another crankshaft sensor symptom). HAS to be a bad crankshaft position sensor. Maybe a new one will cure my bad starts too? Kinda excited to see how it will run with new sensor.
Get new sensor - take it to get installed. Shop calls and leaves message on phone to call them (never good - unless it's the "your car is ready" message, it's never good). I call them and they answer with the line...."Looks like she is finally toast - we put the sensor in and it didn't make a difference - car barely runs - can't drive more than 10 feet without stalling". They went on to mention they found filings on the crank sensor magnet. Well, I guess the scored cylinders have finally caught up with me - I start planning on sending bottom end away to get re-built. Not a good day for me.....
The next day, I go down to pick it up and after fighting with it to start in the parking lot, I clear all codes, just to see if that helps - nope (also noticed a new code - "Improper immobilizer input"????). Pulled battery negative cable to reset - didn't help. Decide to open the hood and hear a loud whistling noise. Run back into shop and ask which specific hose was it that they taped up. They pull the service records and say it's in the front, by the two big intake hoses. I go back out and look everywhere - I don't see any loose/broken hoses, but can hear the whistling noise coming from directly in front of me - finally pull the plastic beauty cover that says "4.5 V-8" and low and behold, I find the broken hose they taped up - turns out this is the PCV hose. Tape had basically come off enough to make a gap and I noticed oil around the gap (which was sucking in air).
Tape it back up with aluminum tape (cloth tape they used had basically melted) and the idle immediately returned to normal. Watched as the 6 mechanics in the shop all looked over at the car when the idle returned to normal. Felt like going back into the bay and saying, ".....you know, before you tell someone their car is 'toast', it might help if you actually OPEN THE HOOD and take a peek before you do that - opening the hood is mechanics 101!!!". Pay the $85 bill to replace the crank sensor and head home. Car now runs wonderfully - no more idle dip, no more misfires. Hasn't run this good in months. New PCV hose (and oil separator diaphragm ordered). Noticed white smoke has stopped (probably because there is now no oil being dumped into the engine due to bad PCV hose). Still getting bad starts though, and every time the car has to crank and crank to start, I get the "Crankshaft position sensor" warning again (no warning if car starts without repeatedly cranking). I"m going to assume the crank sensor is good, seeing as it is new and, now that the PCV hose is not leaking, the car runs fine. A bad crank sensor will cause problems, which I don't have anymore. I'm thinking the crank sensor warnings were showing up due to the bad crank cycling starts (meaning, I didn't need to replace it at all) - the PCV hose was causing the bad idle, misfires and system fault codes.
Now - my questions.....
1. - If I have scored cylinders, when the hell does the car finally give out? It's been a year and a bit of "knock, knock, knock" and the car runs perfectly today. No burning oil. Other than the filings on the crank sensor magnet and the knock noise,, there is no indication the engine isn't running as it should.
2. Is my assumption correct that a bad start (where the starter has to crank for like 4-5 seconds before the engine starts) would lead to a crank sensor warning? And because the car runs perfectly now, would that also indicate the crank sensor is fine?
So, moral of this story is - if you ever have any problems with a rough idle/car stalling/not holding RPM steady - pull that "4.5 V-8" cover and take a peek. I can tell you from experience, once that hose has a slight leak, your car will run like "toast".
A lil' background...
- About a year ago, I started getting the "knock noise" from the engine - then my flex pipes went out (creating a loud exhaust noise, so it was hard to hear the "knock")
- After pipes replaced, knock was still there. Seemed to be the symptom of scored cylinders. Started planning on perhaps a rebuild when the car finally gives up. Added oil stabilizer/valve cleaner for the hell of it.
- Fast forward to this summer - knock still there, but sometimes is overridden by what seems to be a tapping valve or injector noise (this seems to come and go).
Car starter finally gives out (was getting bad starts for a while before starter went) - intake removed (replaced starter, water pump, thermostat, seals, etc). Had them take a look at the top of the vales while in there to see how bad they were gummed up (was going to get them to clean them hoping it would solve valve tick). They report back the valves are as clean as a whistle. Also, car hasn't been burning any oil since last summer.....
Get car back and expect a nice smooth start due to new starter, but am still getting random rough starts - just has more "power" behind them due to new starter (Bosch re-manufacture) - see thread about this here.....https://rennlist.com/forums/cayenne-...l#post17491586
Way better than before though, but not what I expected with new starter. NOTE - after getting car back from shop, they mentioned there was a "broken hose" that need to be replaced - said they taped it up for now until I get new hose. Said it was an "air hose", so I assumed it had something to do with the air pumps they remove for intake removal. Figured I'd get the new hose down the road.
Couple weeks later I start getting a dip in idle/shudder at stop lights/as rpm drops. Oh oh - engine finally starting to go? Did some searching and dipping idle could be motor mounts - figured I'd get them replaced if I pull the bottom of engine out for repair.
Rough starts seem to be getting worse. Usually won't start on first turn of key; have to turn key all the way back, remove, re-insert and try again. Weird noises from starter. Then it starts turning over and turning over and turning over till it finally starts. I now get my first "crankshaft position sensor" warning. Car seems to run fine (minus the slight dip in idle), but starting is a chore. Randomly getting "System fault" (too much air) warnings also. Also. whenever I cleared the codes for crank sensor/system, the car would run worse - you could literally feel it go from a bad idle to a worse idle after clearing codes. Also noticed car was now puffing out white smoke on start up/getting hard on the throttle. Not looking good for the engine/scored cylinders.
One night, after another bad start, the car starts running really bad - getting misfire, system fault and crankshaft sensor warnings. Look up crankshaft sensor symptoms and poor running is one of the symptoms (also noticed mention of a "PCV hose" in doing my searches related to the crank sensor). The next night, the car won't even drive more than 2 minutes without stalling (another crankshaft sensor symptom). HAS to be a bad crankshaft position sensor. Maybe a new one will cure my bad starts too? Kinda excited to see how it will run with new sensor.
Get new sensor - take it to get installed. Shop calls and leaves message on phone to call them (never good - unless it's the "your car is ready" message, it's never good). I call them and they answer with the line...."Looks like she is finally toast - we put the sensor in and it didn't make a difference - car barely runs - can't drive more than 10 feet without stalling". They went on to mention they found filings on the crank sensor magnet. Well, I guess the scored cylinders have finally caught up with me - I start planning on sending bottom end away to get re-built. Not a good day for me.....
The next day, I go down to pick it up and after fighting with it to start in the parking lot, I clear all codes, just to see if that helps - nope (also noticed a new code - "Improper immobilizer input"????). Pulled battery negative cable to reset - didn't help. Decide to open the hood and hear a loud whistling noise. Run back into shop and ask which specific hose was it that they taped up. They pull the service records and say it's in the front, by the two big intake hoses. I go back out and look everywhere - I don't see any loose/broken hoses, but can hear the whistling noise coming from directly in front of me - finally pull the plastic beauty cover that says "4.5 V-8" and low and behold, I find the broken hose they taped up - turns out this is the PCV hose. Tape had basically come off enough to make a gap and I noticed oil around the gap (which was sucking in air).
Tape it back up with aluminum tape (cloth tape they used had basically melted) and the idle immediately returned to normal. Watched as the 6 mechanics in the shop all looked over at the car when the idle returned to normal. Felt like going back into the bay and saying, ".....you know, before you tell someone their car is 'toast', it might help if you actually OPEN THE HOOD and take a peek before you do that - opening the hood is mechanics 101!!!". Pay the $85 bill to replace the crank sensor and head home. Car now runs wonderfully - no more idle dip, no more misfires. Hasn't run this good in months. New PCV hose (and oil separator diaphragm ordered). Noticed white smoke has stopped (probably because there is now no oil being dumped into the engine due to bad PCV hose). Still getting bad starts though, and every time the car has to crank and crank to start, I get the "Crankshaft position sensor" warning again (no warning if car starts without repeatedly cranking). I"m going to assume the crank sensor is good, seeing as it is new and, now that the PCV hose is not leaking, the car runs fine. A bad crank sensor will cause problems, which I don't have anymore. I'm thinking the crank sensor warnings were showing up due to the bad crank cycling starts (meaning, I didn't need to replace it at all) - the PCV hose was causing the bad idle, misfires and system fault codes.
Now - my questions.....
1. - If I have scored cylinders, when the hell does the car finally give out? It's been a year and a bit of "knock, knock, knock" and the car runs perfectly today. No burning oil. Other than the filings on the crank sensor magnet and the knock noise,, there is no indication the engine isn't running as it should.
2. Is my assumption correct that a bad start (where the starter has to crank for like 4-5 seconds before the engine starts) would lead to a crank sensor warning? And because the car runs perfectly now, would that also indicate the crank sensor is fine?
So, moral of this story is - if you ever have any problems with a rough idle/car stalling/not holding RPM steady - pull that "4.5 V-8" cover and take a peek. I can tell you from experience, once that hose has a slight leak, your car will run like "toast".
Last edited by Jeff928S4; 06-14-2021 at 05:23 PM.
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oldskewel (06-15-2021)
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Dilberto (06-15-2021)
06-16-2021, 02:03 PM
#6
The PCV system can be the source of many gremlins, odd symtoms and worse if left alone for too long. This is a classic "an ounce of prevention is worth a pound of cure" situation.
Clogged PCV - Remove oil cap, replace with a disposable glove. If it inflates the glove, the PCV is clogged and you are probably pushing oil and blow by out past your gaskets everywhere as well. Haven't seen it happen with thies engine, doesn't mean it can't
Torn or failing PCV Diaphraghm: A very common problem. You are sucking excess oil vapors and blowby into the intake manifold. You will be consuming oil; eventually you'll destroy your catalytic converters. Good thing they are cheap to replace. Remove the oil cap with the engine running. Now, slowly move it into position like you are going to screw it back on. Did engine suction pull the cap down just as you were about to secure it? That's a sign that the PCV diaphraghm is torn or stuck open and the intake is sucking from the crankcase all the time. You can perform wht same test with the dipstick, just as the o-ring makes contact with the guide tube.
Leaking hose between PCV & Intake? Your engine is sucking un-metered air and running like dog poop. Depending on the size of the leak, it may clear up at higher rpm where the engine is drawing lots of air and a small amount of extra air goes unnoticed.
Turbo engine Bonus round - Check valves: On normally aspirated engines, the pressure differential is always lower on the intake side than on the crankcase side, so the spent gasses flow is a one way street, from the crankcase through the PCV valve into the intake. However, when the turbos are on boost, you could blow 15 psi from the intake past the PCV into the engine and again, blow out your oil seals, or at the very least beat up your PCV until it relents, and then blow out your engine's oil seals. So, there are two little check valves (at least on the 955, assuming similar setup on 957) between the intake and the PCV to prevent boost from blowing back into the crankcase. They are easy to remove and look, internally, like little PCVs with their rubber diaphraghms to prevent back flow. They die too. If it has never been done during your ownership and the PCV is suspect or failing, these would be a no-brainer as well in order to rule the system out as a source of problems. It took longer to type the last paragraph than it does to replace them.
Regards,
Brian C.
Clogged PCV - Remove oil cap, replace with a disposable glove. If it inflates the glove, the PCV is clogged and you are probably pushing oil and blow by out past your gaskets everywhere as well. Haven't seen it happen with thies engine, doesn't mean it can't
Torn or failing PCV Diaphraghm: A very common problem. You are sucking excess oil vapors and blowby into the intake manifold. You will be consuming oil; eventually you'll destroy your catalytic converters. Good thing they are cheap to replace. Remove the oil cap with the engine running. Now, slowly move it into position like you are going to screw it back on. Did engine suction pull the cap down just as you were about to secure it? That's a sign that the PCV diaphraghm is torn or stuck open and the intake is sucking from the crankcase all the time. You can perform wht same test with the dipstick, just as the o-ring makes contact with the guide tube.
Leaking hose between PCV & Intake? Your engine is sucking un-metered air and running like dog poop. Depending on the size of the leak, it may clear up at higher rpm where the engine is drawing lots of air and a small amount of extra air goes unnoticed.
Turbo engine Bonus round - Check valves: On normally aspirated engines, the pressure differential is always lower on the intake side than on the crankcase side, so the spent gasses flow is a one way street, from the crankcase through the PCV valve into the intake. However, when the turbos are on boost, you could blow 15 psi from the intake past the PCV into the engine and again, blow out your oil seals, or at the very least beat up your PCV until it relents, and then blow out your engine's oil seals. So, there are two little check valves (at least on the 955, assuming similar setup on 957) between the intake and the PCV to prevent boost from blowing back into the crankcase. They are easy to remove and look, internally, like little PCVs with their rubber diaphraghms to prevent back flow. They die too. If it has never been done during your ownership and the PCV is suspect or failing, these would be a no-brainer as well in order to rule the system out as a source of problems. It took longer to type the last paragraph than it does to replace them.
Regards,
Brian C.
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Silicon (01-24-2024)
06-16-2021, 10:39 PM
#7
RL Community Team
Rennlist Member
Rennlist Member
The PCV system can be the source of many gremlins, odd symtoms and worse if left alone for too long. This is a classic "an ounce of prevention is worth a pound of cure" situation.
Clogged PCV - Remove oil cap, replace with a disposable glove. If it inflates the glove, the PCV is clogged and you are probably pushing oil and blow by out past your gaskets everywhere as well. Haven't seen it happen with thies engine, doesn't mean it can't
Torn or failing PCV Diaphraghm: A very common problem. You are sucking excess oil vapors and blowby into the intake manifold. You will be consuming oil; eventually you'll destroy your catalytic converters. Good thing they are cheap to replace. Remove the oil cap with the engine running. Now, slowly move it into position like you are going to screw it back on. Did engine suction pull the cap down just as you were about to secure it? That's a sign that the PCV diaphraghm is torn or stuck open and the intake is sucking from the crankcase all the time. You can perform wht same test with the dipstick, just as the o-ring makes contact with the guide tube.
Leaking hose between PCV & Intake? Your engine is sucking un-metered air and running like dog poop. Depending on the size of the leak, it may clear up at higher rpm where the engine is drawing lots of air and a small amount of extra air goes unnoticed.
Turbo engine Bonus round - Check valves: On normally aspirated engines, the pressure differential is always lower on the intake side than on the crankcase side, so the spent gasses flow is a one way street, from the crankcase through the PCV valve into the intake. However, when the turbos are on boost, you could blow 15 psi from the intake past the PCV into the engine and again, blow out your oil seals, or at the very least beat up your PCV until it relents, and then blow out your engine's oil seals. So, there are two little check valves (at least on the 955, assuming similar setup on 957) between the intake and the PCV to prevent boost from blowing back into the crankcase. They are easy to remove and look, internally, like little PCVs with their rubber diaphraghms to prevent back flow. They die too. If it has never been done during your ownership and the PCV is suspect or failing, these would be a no-brainer as well in order to rule the system out as a source of problems. It took longer to type the last paragraph than it does to replace them.
Regards,
Brian C.
Clogged PCV - Remove oil cap, replace with a disposable glove. If it inflates the glove, the PCV is clogged and you are probably pushing oil and blow by out past your gaskets everywhere as well. Haven't seen it happen with thies engine, doesn't mean it can't
Torn or failing PCV Diaphraghm: A very common problem. You are sucking excess oil vapors and blowby into the intake manifold. You will be consuming oil; eventually you'll destroy your catalytic converters. Good thing they are cheap to replace. Remove the oil cap with the engine running. Now, slowly move it into position like you are going to screw it back on. Did engine suction pull the cap down just as you were about to secure it? That's a sign that the PCV diaphraghm is torn or stuck open and the intake is sucking from the crankcase all the time. You can perform wht same test with the dipstick, just as the o-ring makes contact with the guide tube.
Leaking hose between PCV & Intake? Your engine is sucking un-metered air and running like dog poop. Depending on the size of the leak, it may clear up at higher rpm where the engine is drawing lots of air and a small amount of extra air goes unnoticed.
Turbo engine Bonus round - Check valves: On normally aspirated engines, the pressure differential is always lower on the intake side than on the crankcase side, so the spent gasses flow is a one way street, from the crankcase through the PCV valve into the intake. However, when the turbos are on boost, you could blow 15 psi from the intake past the PCV into the engine and again, blow out your oil seals, or at the very least beat up your PCV until it relents, and then blow out your engine's oil seals. So, there are two little check valves (at least on the 955, assuming similar setup on 957) between the intake and the PCV to prevent boost from blowing back into the crankcase. They are easy to remove and look, internally, like little PCVs with their rubber diaphraghms to prevent back flow. They die too. If it has never been done during your ownership and the PCV is suspect or failing, these would be a no-brainer as well in order to rule the system out as a source of problems. It took longer to type the last paragraph than it does to replace them.
Regards,
Brian C.
Cheers,
Tom
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Silicon (01-24-2024)
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06-16-2021, 11:02 PM
#8
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Turbo engine Bonus round - Check valves: On normally aspirated engines, the pressure differential is always lower on the intake side than on the crankcase side, so the spent gasses flow is a one way street, from the crankcase through the PCV valve into the intake. However, when the turbos are on boost, you could blow 15 psi from the intake past the PCV into the engine and again, blow out your oil seals, or at the very least beat up your PCV until it relents, and then blow out your engine's oil seals. So, there are two little check valves (at least on the 955, assuming similar setup on 957) between the intake and the PCV to prevent boost from blowing back into the crankcase. They are easy to remove and look, internally, like little PCVs with their rubber diaphraghms to prevent back flow. They die too. If it has never been done during your ownership and the PCV is suspect or failing, these would be a no-brainer as well in order to rule the system out as a source of problems. It took longer to type the last paragraph than it does to replace them.
Regards,
Brian C.
Regards,
Brian C.
TIA
06-23-2021, 02:34 AM
#9
https://www.fcpeuro.com/products/por...008337#fitment
I resist blindly throwing parts at a problem, but there are a bunch of usual suspects that mimic more serious ones. If you are burning oil or leaking it, this part, along with the PCV membrane/spring & cap are worth a look and easy to change.
I resist blindly throwing parts at a problem, but there are a bunch of usual suspects that mimic more serious ones. If you are burning oil or leaking it, this part, along with the PCV membrane/spring & cap are worth a look and easy to change.
Last edited by BrianC72gt; 06-23-2021 at 03:11 AM.
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TRINITONY (06-23-2021)
06-23-2021, 07:05 PM
#10
https://www.fcpeuro.com/products/por...008337#fitment
I resist blindly throwing parts at a problem, but there are a bunch of usual suspects that mimic more serious ones. If you are burning oil or leaking it, this part, along with the PCV membrane/spring & cap are worth a look and easy to change.
I resist blindly throwing parts at a problem, but there are a bunch of usual suspects that mimic more serious ones. If you are burning oil or leaking it, this part, along with the PCV membrane/spring & cap are worth a look and easy to change.
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GlenC (08-15-2021)
06-24-2021, 05:58 PM
#11
Rennlist Member
06-24-2021, 07:54 PM
#12
Three Wheelin'
All of those junk plastic hoses are going bad. I've replaced most of them with OEM or some Silicone on my '06CTTS. BTW, Why would filings on the Crankshaft sensor be related to Bore Scoring? You are talking about the crankshaft sensor on the bellhousing right? Bore scoring might show up on a magnetic oil drain plug (I replaced both of my with ECS Tuning magnetic ones) or for sure on an Oil Analysis, more Aluminum and higher Silcon.
06-25-2021, 07:13 PM
#13
Racer
Same here. I'm on...probably year 4 of my rebuilt Bosch starter and it still works like a champ. Maybe Jeff and I got lucky?
