rmt52

Hi guys, hoping someone here might be able to provide some insight. Should all four cams the right and left intake and exhaust cams be behaving roughly the same way when idling? I'm trying to figure out why I get a rough idle. My right intake and exhaust adjusters were replaced a few months ago under warranty. I'm wondering if perhaps the left one is going bad. While the max and min position values appear to be very similar for the intake cams (r.intake max: 27.86, min: 26.80, l.intake max:27.58 min: 26.88) the right intake cam position moves around almost 4 times as much, variance is almost four times higher and the left intake cam position variance is almost zero. The (r.exhaust max:-14.03 min:-15.89, l.exhaust max:-13.63 min:-15.17) here the right exhaust cam moves twice as much as the left exhaust cam, variance is double. Does this behavior seem entirely normal?

MJ50

do u get CEL?

rmt52

No. But when idling, especially when the car is cold, the car kind of shakes randomly. You can feel it in the footwell, the pedals, the door or the steering wheel. Theres no knocking noise. But it feels like a shake/thump.

Merc63

What's your timing do when it shakes?

rmt52

I believe the right intake moves a decent amount relatively speaking (1 Kw give or take, on my xentry diagnostic) but the left intake stays pretty much where it is, moves maybe .1 give or take.

Merc63

Ignition timing

rmt52

Hi merc63. What about the ignition timing? Are you asking what it is? I'm out of town tonight and tomorrow but can check Sunday afternoon. Thanks for helping me with this. I appreciate it. One question for you though. Should the position of right intake and left intake camshafts always be the same at the same point and likewise for the right and left exhaust camshafts? Should they be completely in sync or not necessarily?

Merc63

I'd asked roadtalon this, I don't know for sure but I would assume the left and right bank should be very close if not identical, otherwise one bank will be making different power then the opposite side.

I know that when I had a shake at idle with a previous tune that my ignition timing was hunting around and when it would go low, the car would shake and the timing would go back up.

rmt52

One thing I can tell you, is in the past I had looked at the ignition timing and it did bounce around from 15-25 degrees on idle, occasionally dropping below 15. I'd have to double check what it's been showing lately. The car is stock though, no advanced timing.

Also, is there any chance this is at all related to the cams/cam gears making a whining noise on low rev/high load? I've been trying to read up as much as I can, and I've read that if there's not enough cam lash that the engine would be producing noticeable whine, which it has done for a while.

It almost seems to me (as uninformed as I am, ha) that perhaps the timing of the cams is set incorrectly?

roadtalontsi

if the cam timing was off you'd have a code. These engines are very picky. Chances are you have a vacuum leak while its cold and once warm it seals up. A little bit of shake is also perfectly normal when warming up. Id try and find someone elses and compare. You have to keep in mind this is a 500hp n/a motor it's pretty serious. It's not like vtech - there arent a 2nd set of aggressive top end cam lobes. Its one set. As long as both the intakes and both the exhausts match up closely you should be good. Now with that being said if this bothers you so much why dont you take it in to get someone to look at it.

rmt52

thanks for the reply roadtalontsi. It doesn't really go away even when warm. it's just more noticeable when it's cold. Tried spraying some carb cleaner a few weeks back, but didn't really find any noticeable leaks. I test drove another c63 this past weekend and it didn't have this issue.


The intake and exhausts don't seem to be in sync to me (but maybe I'm just really uniformed about this), I recorded it idling while connected to my xentry/das system.


It's going back in next week to the dealer. I took it in before, and they say oh this is normal, but the car didn't used to do that. I know the feel of it really well, and I can say without a doubt, that this (the shake) is definitely a recent issue, what I was getting before they changed the right intake/exhaust adjusters was rattle on WOT and at startup. Whereas what i feel now, is like a thump in coming from the front of the car, though there's no real audible knock noise when it occurs, its just something I can feel in the footwell/pedals/through the door/steering wheel. Regarding the low rpm/high load noise was definitely something else I noticed compared to the car I test drove which didn't make that noise nearly as loud. it's kind of like the power steering noise.

roadtalontsi

those dont seem off. Its normal for it to bounce around a little. Did you relearn the camshaft position teach in with the sds hooked up? If i get a chance ill see what mine look like. The pulse wheels which are what the camshaft sensors look at for position do have to be setup with the special tools. If they didnt do this properly it is possible it is off although reading in specs. Unlikely but you never know. These cars can go through p/s pumps. I think its the high rev's. Mines been noisey for quite sometime but i just tell people its the supercharger

rmt52

right. the supercharger. haha. I forgot I had one too.

I didn't perform the relearn. They said they did when they replaced the right bank adjusters a few months ago. I'll hook it up again when I go home.

thanks for the insight roadtalontsi. I appreciate it.

rmt52

left intake/exhaust cam adjusters ended up needing to be replaced. I guess I'm 4/4 now. Right and Left intake/exhaust adjusters have been swapped out under warranty.

Merc63

Pretty common, they go bad after a while.

rmt52

am a little surprised to be honest, the car has under 30k miles on it, but the symptoms were there from when I first got the car. just took various dealers several several visits till they were able to "verify" the issue being described.

Merc63

They can get really noisy and rattle on start up too. I've replaced two different cars bith at around 60k km