Camshaft deviation guru's....?
 

2001 Boxster S, one owner, mileage 30,000 kms (18,600 mi).

I decided to connect my Durametric pro for the first time to get familiar and check cam deviations as I have been considering getting the LN Solution installed. I try to keep the rpm under 3000 until the engine is at normal operating temp and usually get into the 5-6000k range regularly. I've never hit the rev limiter though.

Went for a 30 min drive and hooked up the durametric when I got home :eek:

Idle cam deviation readings were: Bank 1 (-7.61) Bank 2 (0.53).

I was able to activate the variocam and at idle there was an obvious rpm fluctuation/stumble on both banks when activated. I brought the rpm up to
2800/3000 rpm and deviations were unchanged: Bank 1 (-7.61) Bank 2 (0.53). Actual cam angles increased to Bank 1 (24.66) and Bank 2 (24.83).

It seems that the variocam solenoids and actuators are functioning on both banks which leaves me with a couple of questions. The more obvious to me was that the cam tensioner pads on Bank 1 must need to be changed (but at this mileage?).

Could it be as simple as changing the tensioner on Bank 1?

I spoke with a local Porsche tech who said that when a shop (or dealer) hook up their diagnostics to the car they likely don't dig too deep into the system if there are no codes being thrown. He said he has seen cases where the timing was slightly out...possibly from new, although I'd be surprised if that was the case.

So before I start replacing parts chasing this issue I wanted to lean on you folks who have far more knowledge than I do. I have dropped the oil filter, cut it open an inspected the pleats...they were pristine/clean clean.

The weather is great and I'd love to be out with the top down but I have visions of broken cam pad bits causing the timing to jump a tooth...sheesh!

By the way, during all Durametric testing the cam graph displayed rock steady straight lines with no evident wandering (just the deviation which also remained steady).

Thanks for reading....thoughts pleeze...

your car doesn't code until a deviation of +/- 9 degrees, so i would wait for that. i got a deviation of -16 when my actuators failed (catastrophically) and no valve interference issues so nothing is going to break.

tech is right, i think deviations from the factory can be quite high (mis-aligned sensors). take the -7.61 as a baseline, drive the car, check often. most likely variocam actuator pads are the issue and will continue to deteriorate. this will be evident in an increasing deviation number.

work can be done with engine in the car. be prepared to replace a few other things while in there; chains (cheap) update your three tensioners if needed, and do some hard thinking about replacing your actuators - they are very expensive but do fail, and replacing them while you are in there *might* save the trip back in at a later date - all about your risk tolerance.

Thanks TRK...wow, -16 would scare a lot of folks methinks haha. Yeah, I think I've read every thread here and other forums on cam deviations, did you have actuator green o-ring seal material in your filter?

If what I read is true, shops want the deviations below the +/- 6 degrees before any IMS work. That was why I was checking the deviations to start with.

i had been running at a deviation of around -6 for a while. it was creeping up and i was getting the hard little brown bits in my oil filter, so all made sense then boom, actuator failure, green bits in sump, big jump in deviation.

coincidence? perhaps. or perhaps having the actuator operating a variocam system with a floppy chain hammering worn variocam pads accelerated it's demise (as the porsche +/-9 limit was established before they knew the tensioners and pads would wear so poorly, forcing them to update the parts).

and is the pad wear due mostly to start up rattle due to insufficient oil pressure on start-up? fixed by changing to the updated oil pump piston? or adding an accusump with pre-oiling?

who knows. like the late great kurt said, "just because your paranoid, doesn't mean they're not out to get you" ... drive your car, keep an eye on it, fix it when you find the right combination of time and money.

I had cam deviations of 5.x and 7.x. Local indy who is the big local Porsche shop said not to worry. I took the cams and variocam out and the pads on the 7.x side literally fell apart when I removed the chain. Cam deviations now are in the 2.x range. Replaced pads and chains on both sides. The photo is of the pads on the worst side. http://986forum.com/forums/uploads02...1527625441.jpg

This is what I'm hoping to avoid if possible. Do you recall how many miles were on those pads and did you replace them with the updated version?

Yes, the car is a 2000S and had 67000 miles on it when I replaced the pads. I did use the updated pads (I think those might be the only ones available at this point). The new pads are much lighter in color.

Much appreciated, thank you.

I came across this description of the variocam system and found it interesting. It is an overview of the system that I hadn't seen before, thought it might be worth sharing. It's a short read, my apologies if it has been discussed previously.

https://fifthgear.biz/fifthgear-blog/porsche-quotvariocamquot-oiling-problem-and-premature-engine-failure-more-to-the-story/

The consequence of a total wear pad failure vs the cost of doing the job and considering the history of wear pad failures on these engines lead me to disregard my indie's recommendation to "wait and see." As it turns out my concerns were well founded and my cam deviations returned to normal after the repair. Others have reported different experiences however. I guess it depends on how much risk you're willing to accept.

that's the thing - consequence is not that big? failure just results in a jump in deviation. damage limited to parts that you would change anyways. change in deviation is not significant enough to create valve/piston interference. as opposed to failure of timing chains (and ims) that can make things go bang. that's why yes you should fix it, but don't mothball the car in the interim.

What should a ballpark price be for an indie to change the pads and chains?

I pulled the sump and the uptake screen had all kinds of blue plastic pieces stuck in it.....

How difficult is this job for a moderately experienced (bolt on stuff kinda guy) mechanic to attempt?

2002 base
160k
LN IMS at 130K (previous owner)
I have done: water pump, low temp thermostat
AOS

Also curious - assume they can do this while doing an IMS install?

It is possible, but the IMS and chain pads are not really in the same part of the engine, so there would be considerable labor involved. If it were up to me, I would drop the engine and do everything on a stand before popping the engine back in. Much quicker and easier on the stand.