My mechanic is stumped. Need help from Rennlisters Please.........
05-18-2012, 11:40 PM
#17
Instructor
05-19-2012, 01:40 PM
#19
Race Car
05-21-2012, 10:04 AM
#20
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Meanwhile the work begins today and as long as things go according to plan I should have it back Friday. It's been 3 weeks and I really miss her. Yesterday I was on youtube listening to different porsche exhausts. Nothing beats the growl of a flat 6!
05-21-2012, 04:43 PM
#21
Race Director
I'm not quite sure as well. Maybe another member can shed some light on the subject.
Meanwhile the work begins today and as long as things go according to plan I should have it back Friday. It's been 3 weeks and I really miss her. Yesterday I was on youtube listening to different porsche exhausts. Nothing beats the growl of a flat 6!
Meanwhile the work begins today and as long as things go according to plan I should have it back Friday. It's been 3 weeks and I really miss her. Yesterday I was on youtube listening to different porsche exhausts. Nothing beats the growl of a flat 6!
It would have been interesting/helpful to know the error codes.
IMS/IMS bearing is often the diagnosis but it may not be the right one.
A VarioCam solenoid/actuator can go bad and cause the symptoms you describe. Absent any noise of the marbles in a can and absent any signs of bearing failure in the oil filter housing oil and the filter element...
It is hard to imagine a real bad IMS bearing lasting as long as it did.
I'm also having a hard time imagining how a failing IMS could account for a cam timing variability.
While it is true the crank drives the IMS (via a chain) and the IMS drives the exhaust cams (again via chains) and the exhaust cams in turn drive the intake cams (chains again) unless a chain becomes so loose as the jump/skip a tooth the timing should not be adversely affected.
What can affect cam timing though is if the solenoid (or actuator) fails. The DME adjusts the intake cam timing and then fails to detect the desired timing from the cam position sensors. Assuming the sensors are not bad (there are tests for this) the DME will log one or more error codes pertaining to cam timing.
The engine will continue to run though it can run rough, experience a hunting idle -- in the case of my Boxster which went through this the rpms dropped to around 500 then climbed again and repeated this for as long (not long) as I let the engine idle.
If the failure is a hard failure (compared to as was the case in my Boxster an intermittent failure -- after shutting off the engine, and clearing the error codes the engine started and ran just fine afterwards but I had it in to have the symptoms diagnosed and the engine repaired without any delay -- the engine may stumble or even die as the DME attempts to change the fueling to try to bring the O2 sensor readings into an acceptable range and gets the fueling too far out of whack.
Anyhow, just my two cents (or less) worth.
Sincerely,
Macster.
05-30-2012, 10:32 AM
#22
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It would have been interesting/helpful to know the error codes.
IMS/IMS bearing is often the diagnosis but it may not be the right one.
A VarioCam solenoid/actuator can go bad and cause the symptoms you describe. Absent any noise of the marbles in a can and absent any signs of bearing failure in the oil filter housing oil and the filter element...
It is hard to imagine a real bad IMS bearing lasting as long as it did.
I'm also having a hard time imagining how a failing IMS could account for a cam timing variability.
While it is true the crank drives the IMS (via a chain) and the IMS drives the exhaust cams (again via chains) and the exhaust cams in turn drive the intake cams (chains again) unless a chain becomes so loose as the jump/skip a tooth the timing should not be adversely affected.
What can affect cam timing though is if the solenoid (or actuator) fails. The DME adjusts the intake cam timing and then fails to detect the desired timing from the cam position sensors. Assuming the sensors are not bad (there are tests for this) the DME will log one or more error codes pertaining to cam timing.
The engine will continue to run though it can run rough, experience a hunting idle -- in the case of my Boxster which went through this the rpms dropped to around 500 then climbed again and repeated this for as long (not long) as I let the engine idle.
If the failure is a hard failure (compared to as was the case in my Boxster an intermittent failure -- after shutting off the engine, and clearing the error codes the engine started and ran just fine afterwards but I had it in to have the symptoms diagnosed and the engine repaired without any delay -- the engine may stumble or even die as the DME attempts to change the fueling to try to bring the O2 sensor readings into an acceptable range and gets the fueling too far out of whack.
Anyhow, just my two cents (or less) worth.
Sincerely,
Macster.
IMS/IMS bearing is often the diagnosis but it may not be the right one.
A VarioCam solenoid/actuator can go bad and cause the symptoms you describe. Absent any noise of the marbles in a can and absent any signs of bearing failure in the oil filter housing oil and the filter element...
It is hard to imagine a real bad IMS bearing lasting as long as it did.
I'm also having a hard time imagining how a failing IMS could account for a cam timing variability.
While it is true the crank drives the IMS (via a chain) and the IMS drives the exhaust cams (again via chains) and the exhaust cams in turn drive the intake cams (chains again) unless a chain becomes so loose as the jump/skip a tooth the timing should not be adversely affected.
What can affect cam timing though is if the solenoid (or actuator) fails. The DME adjusts the intake cam timing and then fails to detect the desired timing from the cam position sensors. Assuming the sensors are not bad (there are tests for this) the DME will log one or more error codes pertaining to cam timing.
The engine will continue to run though it can run rough, experience a hunting idle -- in the case of my Boxster which went through this the rpms dropped to around 500 then climbed again and repeated this for as long (not long) as I let the engine idle.
If the failure is a hard failure (compared to as was the case in my Boxster an intermittent failure -- after shutting off the engine, and clearing the error codes the engine started and ran just fine afterwards but I had it in to have the symptoms diagnosed and the engine repaired without any delay -- the engine may stumble or even die as the DME attempts to change the fueling to try to bring the O2 sensor readings into an acceptable range and gets the fueling too far out of whack.
Anyhow, just my two cents (or less) worth.
Sincerely,
Macster.
Thanks for the info. I printed your post and passed it along to the shop manager. Mechanics can be a little sensitive sometimes. Here are some pics from my visit yesterday.
05-31-2012, 01:34 AM
#23
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Well it looks like the shop already got stuck into doing as they wish to your engine and whatever they say needs replacing will get replaced. Good job you have a warranty out on it. I think your warranty people will be involved and giving the go ahead with new parts or reconditioned ones. With any luck you just might finish up with a totally rebuilt engine even though it might have only been a simple thing as Macster suggested like a failed actuater. Would be nice for you to get hold of any old parts that they change so you can inspect the damage. Like the dreaded XXX bearing if it was changed. Anyway enjoy your new car to the fullest. 
05-31-2012, 02:16 PM
#24
Under no circumstances is this an IMS failure. Please post the codes (ask the mechanic to just write down the numbers, we'll take it from there.) Without the codes there are just to many suspects.
05-31-2012, 02:56 PM
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He did say that it wasn't just error codes but that the timing was actually off which I saw for myself.
Got there just as they were pulling the trans off and you could also see the area around the bearing enclosure definitely had seepage. Here's a pic....................
The way I see it is that if its something else he'll find it and in the mean time I'm getting the new LN Bearing for free.
05-31-2012, 05:58 PM
#27
Race Director
Not trying to be your long distance mechanic, just offering my thoughts on the situation. My comments are meant to provide you with some discussion points that a mechanic worthy of the name should be willing to discuss with you to your satisfaction.
I can't recall if this has been done but it not removing the oil filter housing and carefully dumping its contents into a *clean* drain pan and looking at the oil and the filter element can help one determine what's going on.
If the IMSB is going bad there will be signs of this in the filter oil and element.
But you must be sure the drain pan is *clean* *clean* *clean*. A false positive at this stage can be an expensive mistake.
Sincerely,
Macster.
I can't recall if this has been done but it not removing the oil filter housing and carefully dumping its contents into a *clean* drain pan and looking at the oil and the filter element can help one determine what's going on.
If the IMSB is going bad there will be signs of this in the filter oil and element.
But you must be sure the drain pan is *clean* *clean* *clean*. A false positive at this stage can be an expensive mistake.
Sincerely,
Macster.
05-31-2012, 07:44 PM
#28
Drifting
Check for debris in oil.
How was cam timing shown to be off?
We check for position of CAM slots relative to valve cover alignment by removing the cam plugs.
If off then we pull the scavenge pump covers and inspect the cam locking bolts.
This can all be done with engine in the car -- heck so can the IMSR.
You can also pull the valve covers and inspect the cam chain rails, if one of those
broke or chipped off, it would affect one sides timing.
You can get one side if the IMS to one bank chain jumped.
The only way to get both sides off is if the Crank to IMS changed relative position.
We had 99 Boxster have the IMS sprocket slip, but I'm told that is only known
to have happened on bicycle chain IMS's which were phased out somewhere around
99-2000.
It is also possible that your timing chain tensioner wasn't working properly and you jumped a tooth,
this would knock both sides off. However I would not think that it would have gotten better
with just changing the CPS.
Note it is possible that it jumped one tooth before (maybe bad -- but not catastrophic??) -- and now has jumped more than one tooth.
Love to know the end result.
thanks,
mike
How was cam timing shown to be off?
We check for position of CAM slots relative to valve cover alignment by removing the cam plugs.
If off then we pull the scavenge pump covers and inspect the cam locking bolts.
This can all be done with engine in the car -- heck so can the IMSR.
You can also pull the valve covers and inspect the cam chain rails, if one of those
broke or chipped off, it would affect one sides timing.
You can get one side if the IMS to one bank chain jumped.
The only way to get both sides off is if the Crank to IMS changed relative position.
We had 99 Boxster have the IMS sprocket slip, but I'm told that is only known
to have happened on bicycle chain IMS's which were phased out somewhere around
99-2000.
It is also possible that your timing chain tensioner wasn't working properly and you jumped a tooth,
this would knock both sides off. However I would not think that it would have gotten better
with just changing the CPS.
Note it is possible that it jumped one tooth before (maybe bad -- but not catastrophic??) -- and now has jumped more than one tooth.
Love to know the end result.
thanks,
mike
