Camshaft deviation question

[san rensho]

My camshaft deviation is steady short term, but it does creep based on engine temperature. Cam 1 deviation (the IMS side) varies almost 1 degree, hot to cold. It starts off around a little less than -6.5 when its cold and goes down to a little over -5.5 when hot. Last time I recorded the values severall months ago the variation was about .3 hot/cold. Cam 2 deviation is about .3 hot/cold and has remained the same over time.


Is this something I should be concerned about? Signs of impending IMSB failure? I checked the oil filter about 500 mile ago and there was no metal in it.

[JFP in PA]

Sounds more like one VarioCam unit may be developing an issue. The limit is supposed to be +/-6, so you are already slightly out. The fact that the amount of deviation changes as the engine (and oil) warm up tends to lean in that direction.

IMS related deviation values tend to swing back and forth wildly at idle, in indication of slop in the cam drive. You are not seeing that.

[Meir]

Hi JFP.
just out of curiosity.
What will be the procedure to get the cams back to the correct values ?
Will it be Replacing all pads and tensoners?
Replacing the electric solenoids?
Or there is another method to adjust the cams to spec.
Thanks in advance.
Meir.

[san rensho]

Ah, makes sense. I recently had a stored fault code for the bank 1 camshaft . Looks like a variocam in the future. Well, it lasted 130k miles.

[san rensho]

Meir, heres the procedure for setting the camshafts.

DIY: Setting Cam Timing on M96

[Dave928]

your link says ... "this applies to non-variocam plus M96 motors (basically, the early ones)"

i had similar numbers, -6.5 and -5.5. had the tensioner pads and solenoids replaced a couple weeks ago. on one side the pads were definitely worn, and look like some sort of chemical reaction (to the oil maybe?) was pitting them. the other side's pads were worn, but no pitting.

$3500. the solenoids are about $220 each. my shop said i didn't need them, but with 100k and 12 years on the car, i figured good insurance. it's a hefty bill to go in there and do it again.

[Meir]

Originally Posted by Dave928

your link says ... "this applies to non-variocam plus M96 motors (basically, the early ones)"

i had similar numbers, -6.5 and -5.5. had the tensioner pads and solenoids replaced a couple weeks ago. on one side the pads were definitely worn, and look like some sort of chemical reaction (to the oil maybe?) was pitting them. the other side's pads were worn, but no pitting.

$3500. the solenoids are about $220 each. my shop said i didn't need them, but with 100k and 12 years on the car, i figured good insurance. it's a hefty bill to go in there and do it again.

that is what i was thinking when i read the post.
however, looking in my Bentley book, i understand that all M96 engines has the verio cam. in the old ones its more like on/off switch, with the newer (03 and up if remember correctly) it has multiple position.
i'm sure someone here can correct me if i'm wrong, or explain it in a better way.
putting that aside, did replacing the pads and solenoids fixed your cam deviation?
if so, what is your value now? and do you feel signification difference in engine power?
thanks in advance.
Meir.

[Dave928]

yeah scratch that first part, i didn't see the "plus" part... oh well.

i didn't see the numbers, but i asked the shop to check them before and after the work, and they say it's good now.
i think the idle is a little more steady. not really a power difference, maybe a little smoother. my understanding is the cam deviation really only effects idle, not cruise operation.

my original problem was that after installing a full aftermarket exhaust, the car idled like crap, popping and backfiring and fuel trim numbers way lean. we tried all sorts of things, nothing fixed it. it ran fine with the MAF unplugged, which should indicate a bad MAF, but it did the same thing even with a new MAF. the only thing the shop could think of was that the deviation was out far enough to maybe cause the freer-flowing exhaust problems. maybe too free flowing? who knows.

i'm going to drive it for a while with the stock exhaust, then put on the new exhaust maybe after new years. i don't like having $2k worth of polished pipes sitting in a box in my garage.

[cbracer]

The 97-99 had variocam but it was on/off, two position. The 00+ have variable variocam which varies the position between the two on/off extremes of the earlier ones. For sure a better way, but nothing that's a magic bullet for power.

My tensioner pads were worn too, one was horribly worn and pitted. It's the one with the oil hole as they tried to keep oil on it to prevent wearing. Looks like it would break at 200k if not replaced before.

I also have deviation on one of the sides but everything I've tried never corrected the problem so I gave up.

[Dave928]

the new pads should have corrected it.

same here, one side pitted, the other not. shop said they all come out like that.
new ones seem to be a different material.