I think I may have the dreaded IMS issue....

[prodwell]

2002 Boxster with 76K miles on it.

Honestly, everything on the car works and sounds great to an un-trained ear however I recently purchased the Durametric software and was starting to investigate the Camshaft Position 1 Deviation and the Camshaft Position 2 Deviation. If I understand Wayne's book and article correctly I should be seeing 0.

On my car for Camshaft Position 1 Deviation is reading -6.17 Crk and Camshaft Position 2 Deviation is reading -2.41 Crk. Both values remain steady at these readings even when increasing the RPM's.

Since these numbers are not 0 does that indicate a problem?

I would really like to save this engine before it blows and could get the bearing replaced but I also use the car as a daily driver too.

What does everyone think?

Thanks in advance for your help.
-paul

[Dale_K]

I have the Durametric too and I know my variation isn't zero but I don't know what the acceptable range of values are. There's a guy selling a IMS failure detection unit if you're getting stressed out.

[JFP in PA]

Originally Posted by prodwell

2002 Boxster with 76K miles on it.

Honestly, everything on the car works and sounds great to an un-trained ear however I recently purchased the Durametric software and was starting to investigate the Camshaft Position 1 Deviation and the Camshaft Position 2 Deviation. If I understand Wayne's book and article correctly I should be seeing 0.

On my car for Camshaft Position 1 Deviation is reading -6.17 Crk and Camshaft Position 2 Deviation is reading -2.41 Crk. Both values remain steady at these readings even when increasing the RPM's.

Since these numbers are not 0 does that indicate a problem?

I would really like to save this engine before it blows and could get the bearing replaced but I also use the car as a daily driver too.

What does everyone think?

Thanks in advance for your help.
-paul

Theoretically, camshaft deviation values should be zero, but in the real world they never are, and you usually end up with some weird +/- values due to tolerances or wear. Even very carefully assembled engines that have gone through very carful static cam timing show this type of discrepancy.

As far as being a predictor of a pending catastrophic engine failure, the only indication that is happening that I am aware of is when the deviation values dance back and forth at an idle; or during a transition from throttle open to closed takes place. Even then, the movement of the values is quite pronounced, indicating that something that shouldn't be moving around is doing just that, usually the IMS bearing.

I believe the accepted deviation value limit, VarioCam or VarioCam Plus, is +/- 6 degrees, and is based upon how far out a cam would be if it were installed one tooth off, which would be the same for either type of cam control system.

As your one cam is near the limit, I would keep an eye on it, but not be overly concerned. I have one customer that has had one cam at 5.87 since the car was new, now at about 65,000 miles. The number never changes.

[drl911]

What did you pay for this evaluation? What would be the average charge for having this checked at the dealer or private Porsche shop?

I just bought an '01 Boxster S with 155,000 miles that runs "perfect", but has original clutch and IMS bearing. Every routine service was done at the local dealer including RMS under warranty at ~42,000.

Thanks,
Dan

[JFP in PA]

Anyone with a Durametric system, or either a PST II/PIWIS system, can read these for you. It only takes a few min. to do, so you should be able to get them done for a minimal diagnostics charge (varies from shop to shop). Should look something like this:

[dharder]

Just replaced the IMS bearing in my '98 Boxie with 98k miles along with the clutch and some other stuff. The original reason for breaking it open wasn't the IMS but the clutch-it was slipping intermittently. I should have known that the clutch would fail as the guy I bought it from (at 57k miles) used to hold the clutch in at every stop light and hold it till the light turned green. As it turns out, the IMS hadn't started coming apart but it was stiff to turn. The clutch, on the other hand, came out as a cup of dust, the disk was down to the rivets, and the throw-out bearing was almost un-turnable. After I got it all back together, I thought I'd screwed something up because the clutch pedal went to the floor with little resistance. That's the way it's supposed to be...

The process was a bit of a journey. It took me 20 total hours of work with no major issues. I have a nice shop with a lift and almost every tool known to mankind. I ordered the clutch kit from Pelican and I ended up cowboy-ing up and getting the ceramic IMS bearing. The bearing puller (can't remember the brand but I got it through Pelican) and installer were invaluable. I couldn't have done the job without these. The only stumbling block was that one of the bolts that attaches the tranny to the engine was a 10mm 12 point star type. Didn't have one of those and it was late saturday afternoon when I needed it. Found one at a nearby auto parts store.

Car shifts like it never did.

[newlife]

Originally Posted by dharder

Just replaced the IMS bearing in my '98 Boxie with 98k miles along with the clutch and some other stuff. The original reason for breaking it open wasn't the IMS but the clutch-it was slipping intermittently. I should have known that the clutch would fail as the guy I bought it from (at 57k miles) used to hold the clutch in at every stop light and hold it till the light turned green. As it turns out, the IMS hadn't started coming apart but it was stiff to turn. The clutch, on the other hand, came out as a cup of dust, the disk was down to the rivets, and the throw-out bearing was almost un-turnable. After I got it all back together, I thought I'd screwed something up because the clutch pedal went to the floor with little resistance. That's the way it's supposed to be...

The process was a bit of a journey. It took me 20 total hours of work with no major issues. I have a nice shop with a lift and almost every tool known to mankind. I ordered the clutch kit from Pelican and I ended up cowboy-ing up and getting the ceramic IMS bearing. The bearing puller (can't remember the brand but I got it through Pelican) and installer were invaluable. I couldn't have done the job without these. The only stumbling block was that one of the bolts that attaches the tranny to the engine was a 10mm 12 point star type. Didn't have one of those and it was late saturday afternoon when I needed it. Found one at a nearby auto parts store.

Car shifts like it never did.

Wow, great post and thank you for sharing this.

Rod

[NOTASIX]

This sounds like the cam timing needs to be readjusted, OR you have a lazy variocam servo. The servos can become dirty or have debris enter them and cause these deviations.

It is also VERY common to have IMS sprockets slip on the IMS drive tube, which will also create these deviations and require readjustment of the cam timing. The sprocket on the crank pulley end of the IMS drive tube is a very questionable fit and its common place to see this slip and create deviations like those that are described here.

I doubt this is an IMSBF in the early stages, because the deviations would vary between idle and higher RPM, which is what we see frequently. When I see non variable deviations I immediately question the IMS drive sprocket slippage or the fact that some engines seem to have been mis-timed from day one-

You might want to consider doing some invasive work while its still an elective procedure. I seriously doubt this is the IMSBF mode of failure about to strike.

[clickman]

Originally Posted by dharder

I should have known that the clutch would fail as the guy I bought it from (at 57k miles) used to hold the clutch in at every stop light and hold it till the light turned green.

Pardon my ignorance, but why is this bad?

[drl911]

It's not "bad" and has no impact whatsoever on the wearing of the fiction plate (or flywheel). It does put an axial spring load on the throw out bearing, but it is designed for that... the unit isn't even spinning when the car is stopped. The root problem is the envirnoment in the bell housing is not very good for bearings with clutch dust coating everything.

[dharder]

When the clutch pedal is held in, pressure is applied to the throwout bearing which is held against the tines of the pressure plate. This, along with the syncros in the transmission, allow the clutch disk to stop spinning. The clutch disk is splined and attached to the transmission shaft. When the tranny shaft stops spinning, you can hopefully shift the car in to gear. Also, when the clutch is held in and the tranny shaft stops spinning, the engine flywheel still spins. There is a pilot bearing/bushing in the end of the flywheel that comes into play when shifting.

Holding the clutch pedal in at stop lights isn't the end of the world but, in my opinion, is a bad habit to get into as it can cause premature failure of the throwout bearing and/or pilot bearing/bushing. When the throwout bearing/pilot bearing/bushing fail, the clutch fails.....