The Forever CEL

[Ahsai]

If the color links line up at the beginning, that's all that matters. Once you turn the crank/cams, the matching relationship will be lost, until n turns later. I don't recall but n is probably a large number.

 

Of course in additon to the links lining up, you still need the proper cam timing tool to set the timing accurately. Using the stock tensioner to maintain tension is probably ok.

[Ahsai]

One thing comes to mind. Make sure the cam reluctor did not slip and rotated out of its original position. I think there's a tab to fix the reluctor so shifting should not be possible but I don't quite remember now.

[Ahsai]

Do you have this timing tool?

 

 

[vza]

OK ...so I'm good (in reference to losing the match on the links) not too sure what 'n' means.(crank rotations?) Ah ...Cam reluctor? Is that the tab that the sensor reads? Well the tool is another story. I had the simpler tool that pelican shows in their dIY couldn't get it to fit in and bolt on either bank called manufacturer and they said they had machining and spec issues with some batches ,sent another ….same thing ,then ordered the tool you pictured and I just couldn't get it in with the engine installed ...too big. So...I scribed a line to the outside of the Puck(from 1st tool) that drops in so I can line it up with the cam cover seam and eyeballed it. I mean I was so meticulous with this step and if there is any error its by a millimeter I was sure I was dead on (worked on bank 2 with 0 deviation) unless of course it slipped . I'll check it and see ...I mean I don't plan on pulling the cam cover off again ...just the scavenge pump(which was very difficult to get back In without backing off on a few cam cover bolts in the area) to re-do timing. Thanks again for the and your help.hopfully get this fixed. v

[Ahsai]

Yes, n is just the number of turns of the crankshaft. I'm sorry to say but you cannot eyeball the timing. The proper tool is needed. The reason is it takes 2 turns of the crankshaft (720 degrees) for one cam to turn 360 degrees. I.e. if the cam is off by 5 degrees, the crankshaft will be off by 10 degrees. Your current -15 degree off is referred to the crank. That means your cam is "only" 7.5 degrees off and that's enough to cause misfires.

[Ahsai]

Before you do anything, could you plot actual cam angle of BOTH banks and compare them when you rev the engine up and down?

Some cases the cam actuator is "lazy" that can also cause misfires. It should be obvious if you compare between the two banks.

 

I think if you really need to eyeball the timing, you could try to err on the side that gets you more positive cam deviation (since cam deviation will keep going more negative as the cam pads  wear). BTW, do you use blue loctite on the cam sprocket bolts? Also, make sure you turn the crank at least 6 to 8 complete turns and recheck the timing every 2 turns before you button things up.

Edited April 25, 2019 by Ahsai

[vza]

OK..lot of info...first off how do I plot the cam angle...would be interested in that.. Yes I did use blue Loctite...don't think I turned it over 6 times. I'd be lucky if the timing just slipped that would be an easy fix but I'm doubtful. If my cam is off by 7.5 degrees how does that translate to what lines up with cam cover seams....is it noticeable or microscopic? Thanks again v

[Ahsai]

Under DME, actual values, same place you read the cam deviation. It's called "actual cam angle". If you select graphical display, Durametric will plot the values in real-time. Then you just rev the engine and see how the readings change. Your variocam is on/off so the actual should change cleanly and quickly at the transition points.

 

No idea how 7.5 cam degrees translate to lining up with the cam cover seam but probably noticeable. You need to turn the crank at least that many times to recheck timing in case something has shifted.

[vza]

Hi, There wasn't an option for actual cam angle under 'engine" or 'actual values' nothing to monitor misfires either I don't have a drop down menu for DME... am I missing something? is it possible its called something else? v

[Ahsai]

Um, that's strange. Perhaps your DME doesn't support it. I know the 996 3.4 and 3.6 both support the misfire counters (per cylinder) and the actual (absolute) cam angle.

 

Perhaps some Boxters/Durametric users can chime in.

[vza]

I'll give durametric a shout. v

[vza]

Was just doing some Boxster meditation and thought of something while waiting to get the car up on stands again. The timing did already slip once already on bank 1. I do notice a sound that could be chain rattle on start up. Sort of sounds like a diesel engine on start up and immediately goes away. I'm thinking if Bank 1 did slip again maybe the cause is a failing tensioner.  Is what i'm describing chain rattle?? Thanks V

[Ahsai]

Boxster meditation haha. I like it.

 

Yeah, sounds like the chain tensioner. Perhaps also why it didn't put enough pressure on the chain while you did the timing, causing the inaccurate timing. May not be a bad idea to get a new tensioner. 

[vza]

OK...so good news I guess...you were correct in checking the timing ....it did move again. Cam is rotated too far counterclockwise if that would confirm a negative deviation value. Does the oil need to be drained to pull the scavenge pump and replace the tensioner? (probably so) would be easier to leave oil in, adjust timing,replace tensioner and start it up. Does having 0 degrees deviation insure the cams are timed correctly? The pictures posted show the 'puck' inserted on the exhaust cam, if you look closely you'll see my scribed line and see how much it's off(does this represent 7.5 degrees?) with the seam. The other pic shows the locking tool and how far it's off from the treaded bore where the bolt goes. I assume the tensioner I'm replacing is the one on Bank 1 located underneath the scavenge pump. I don't plan on pulling the cam cover so I won't be able to check the links or dimples on the cams. I'm going to go for just a re-time then lock down the cam and replace the tensioner on Bank 1 side (cause I guess that's why I may be losing the timing....twice now) and see if my deviation gets straightened out.

Also, is the tensioner the IMS tensioner Part #: 996-105-180-59. Thanks Again V

[vza]

If you shifted the grooves counter clockwise to line up where the arrows are in the pic below(stock photo) that would be where my timing is now for Bank 1.

Just to clarify. 

Edited April 28, 2019 by vza

[Ahsai]

Yes, the oil needs to be drained for the bank 1 tensioner to be replaced. If you drain the oil to a clean container, the oil can be reused.

 

The IMS tensioner p/n is correct.

 

Yes, cam deviation = 0 means your cams are timed perfectly. The spec allows +/-6 degrees from 0 degree so you do have some tolerance.

 

Based on your description, your cam is lagging behind the crank because the engine rotates clockwise and that:s exactly why the cam devitaion is negative (lagging). It does look like 7 degrees or more off to me. You can estimate. A full circle is 360 degrees...

[vza]

OK....so it looks like that is the problem.....the timing. It looks like 7 or more degrees on the pic dosen't it!! The tensioner I would replace (because of the loss of timing and the chain rattle) would be the the IMS tensioner as mentioned (maybe getting weak or worn). Just confirming. I had hard time getting the scavenge pump back in last time. Is it ok to back a few of the cam cover bolts out(near to the pump) without the risk of breaking the seal on the cam cover creating a leak. What do you think?  OK I'll give it a try. See what happens!! Thanks V

 

 

 

 

Edited April 29, 2019 by vza

[Ahsai]

Yes, that slot is a mile off where it should be. Cam deviation readings don't lie.

 

I would not recommend you breaking the cam seal like that but yes some scavenge pumps are really a tight fit.

[vza]

OK I'll do my best with scavenge pump. A little confusion w part number and tensioner. I'm replacing the tensioner located on Bank 1 side and accessed from the bottom not the side as in bank 2 ...correct? This is called the IMS tensioner? Is there an updated tensioner with a pre-tension spring or is that for a 911. Sorry want make sure I'm replacing correct one for chain noise. I guess I have to time the bank 1st and replace the tensioner afterwards because I can't lock the crank and cam down the way it is now ….correct?.v

Edited April 29, 2019 by vza

[Ahsai]

The bank1 cam chain tensioner accessed from the bottom is 99610518602. This is the one you should replace.

 

The IMS tensioner, accessed on the side on bank2 is 99610518059. You can optionally replace it too.

 

If you can lock the cam some how with the crank at TDC, you can replace the tensioner first. If not you can time it first then replace the tensioner, then re-time it again if timing has slipped which is possible if the current tensioner is too weak.

 

 

[Ahsai]

Btw, to find the right parts. Autoatlanta has the best parts diagrams.

 

http://www.autoatlanta.com/porsche-parts/hardparts.php?dir=986-97-04&section=103-10

[vza]

OK thanks,I was using pelican as a reference and they have them listed backwards. v

 

[vza]

OK, Finally got back to re-timing bank 1. Just to recap Bank 1 was at -15 Deviation and was determined bank 1 slipped timing. Re-timed bank 1 and replaced chain tensioner. Set it.... bang on ...checked it with my little puck and put my cam lock tool on it and it all lined up perfectly. Spun the crank a million times re-checked still bang on. Re-assembled everything(by now you know where it's going right?) started her up... 20 min warm up or more. Bank 1 is now at -17 deviation......2 degrees worse.(AAhhhhhh.....)Bank 2 still remains at 0. Shut it down and re-checked the timing on Bank 1 and it still is bang on....so slipping.Now I didn't drive it ....it is still up on the stands, didn't clear the CEL. I don't know if driving it and putting it under load would make a difference....I doubt it. Does this mean my cam to cam allocation is off. I can't wrap my head around it! Now what???? Thanks V

Edited June 2, 2019 by vza

[Ahsai]

Since the timing is physically verified, I think you could just reset the DME, disconnect the battery for 30min and then test drive it and rescan it. There's nothing left to do anyway?

[vza]

Hmm...so you're still hopeful...thats good. You think the DME just needs to be reset? Quick question:

Is there anything else that would cause the -17 deviation?

ie. If the timing was off by a tooth or roller between the cams would that cause my problem? (hope the answer to that is no.)

thanks v

Edited June 3, 2019 by vza