311Formula

I joined this site after reading some VVT post about LS1's. Seems like people on this site actually work on thier cars as I do . Most of the caddy forums are desk jocky's bench racing off of the internet inforamtion not actually using tools and taking things apart.

I was hoping someone from this site my have some useful information that could help solve an issue I am having.
I have an 06 cadillac sts with the 4.6 northstar lh2 rwd version. The engine is dohc vvt on all 4 cams. I blew a head gasket on the original engine. I picked up a low mile...(what ever that means) 07 LH2 and have installed it in the car. I worked out some of the small issues ( all fuel injector clogged) and have the car running good. The issue is, it keeps throwing exhaust cam over timing codes on bank 1.

I have chnaged oil multiple time to flush engine.
Replaced the spring loaded oil actuator in the from of that exhaust cam.
Changed the phaser magnet on that cam.
Verfied phaser operation on the rest of the cams by manually applying voltage the the magents indiviually, all tested good.
Replaced the cam sensors.. all four

I am wondering if the oil pressure driven timimg chain tensioer in the front timing cover for that bank of camshafts may not be working or is stuck. If so it should affect both cams I would think???

Or possibly a clogged oil passage to that cams VVT. Not sure how I would check that?
Or if I need to install the ECM out of the car I took the newer engine out of. I do have that ECM.
Name of a very competant shop, west coast area that works on this stuff.

BudRacing

iTrader: (3)

What is the approximate mileage on the "low mile" takeout?

If the sensors check out, I would suspect that it's perhaps a physical issue (provided it's running poorly). It wouldn't be the first time a Northstar jumped a tooth. My mom's 95 Aurora had a similar issue about 10 years ago. It only had 138k on it. Not exactly a "Northstar," but it shared a lot of the DOHC architecture.

311Formula

Thank you for the reply..The mileage is supposably 50k. When there are no codes present that engine runs perfectly. When the code is set, engine runs smooth but has hesitation of idle and seems down on power.

BudRacing

iTrader: (3)

I would say those running symptoms match the code indicated. A mistimed exhaust valve event would choke the engine with those results. If I had the same symptoms and had ruled out a sensor issue with known good ones, I'd be pulling a valve cover to visually confirm that the chain had/hadn't jumped and if so, remediate the tensioner that allowed it to happen. With tensioners, I believe age is just as much a determinant of condition as mileage.

PLA TME

iTrader: (1)

Ok, I can't confirm because I have looked it up yet. The dohc gm v6 like the 3.6 that is used in everything has a notoriously bad chain stretch problem. So much so that acdelco has a service kit will all the parts you need and none you don't for the "low mile" repair.

my wife's 2.8t srx needed this job at 75k after running on synthetic for most of its life. Looking at the chains side by side and you could see that each bank chain was nearly an entire link longer. This puts each cam out of phase with eachother because there is no tensioner between the cams. The tensioner between the head and block keeps the lead cam in line with the crank which is why you aren't seeing more faults just the one for the single cam.

Again this is on the various v6 motors, if the 4.6 is similar 3 chain drive then potentially same issue.

when the fault sets the vvt shuts down causing the low performance.

do some research on timing chains for that motor and you'll likely have your answer.

311Formula

Yep... sounds like the front cover and valve covers are coming off. Anyone have any spare time I could buy....

AAIIIC

iTrader: (19)

I'm not sure which "caddy forums" you looked at that are just desk jocky's [sic], but if you go to the STS forum or the Northstar forum on cadillacforums.com you'll find all the N* experience and information you could ever need.

voodoochikin04

iTrader: (3)

Yea that's what I thought.. after 7years of being on caddy forums, I never saw much desk jockey action. Most everyone worked on their cars.

Also as I was reading I came to the same conclusion and totally agree that it sounds like a stretched timing chain.