2007 Tahoe Timing Chain Replacement

@imadub - the oil pressure is funky, it used to always be around 48-52 at 2,500 rpm and 25-30 at idle but this winter it had a heck of a time holding oil pressure. Now that it has warmed up it hold 15-18 at idle and 30-32 at 2,500 rpm. I am thinking the oil pick-up seal is cooked, also weak oil pump all due to miles. I did try and fill it with another coupel quarts of oil and tried to find an incline to see if the oil pressure increased. It did slightly, however, I am not sure I was on enough of an incline either.

The reason for replacement of the timing gear/chain, I am getting the code P0016. I don't have any analysis tools but its pretty hard to start and once it does it runs kind of rough. I guess I was thinking the tensioner probably crapped out but I am not hearing any extraordinary noise though? I did take a breaker bar and socket to tried to move things to see if there was much play and there seem to be some, maybe 1/2 inch - I know not very scientific but...

I thought about it being a crank sensor also and entertained the idea of replacing it to see, heck of a lot less work than the timing chain project.

Anyway, long winded response to your question.

Thanks,
Tim

Has a cam/crank correlation been done? And if you do change the crank position sensor, be sure to do the correlation with a capable scan tool.

Plimbob said:

@imadub - the oil pressure is funky, it used to always be around 48-52 at 2,500 rpm and 25-30 at idle but this winter it had a heck of a time holding oil pressure. Now that it has warmed up it hold 15-18 at idle and 30-32 at 2,500 rpm. I am thinking the oil pick-up seal is cooked, also weak oil pump all due to miles. I did try and fill it with another coupel quarts of oil and tried to find an incline to see if the oil pressure increased. It did slightly, however, I am not sure I was on enough of an incline either.

The reason for replacement of the timing gear/chain, I am getting the code P0016. I don't have any analysis tools but its pretty hard to start and once it does it runs kind of rough. I guess I was thinking the tensioner probably crapped out but I am not hearing any extraordinary noise though? I did take a breaker bar and socket to tried to move things to see if there was much play and there seem to be some, maybe 1/2 inch - I know not very scientific but...

I thought about it being a crank sensor also and entertained the idea of replacing it to see, heck of a lot less work than the timing chain project.

Anyway, long winded response to your question.

Thanks,
Tim

Click to expand...

If a chain had enough wear in it to allow that much slack, it'd likely be broken. Hard starts and rough operation are classic symptoms of a faulty camshaft position sensor. I'd definitely swap that before diving into the engine for the timing chain. As @Fless mentioned, a CASE relearn will be necessary. Ideally, this is initiated with a bi-directional scan tool. Supposedly, it can be done without by doing the following:

1. Turn off all of the accessories. With the Air temperature sensor and Coolant temperature within 5 degrees (Centigrade) of each other, start the engine and let it idle in Park or Neutral for two minutes.
2. Accelerate the vehicle to 55 mph at part throttle. Cruise at 55 mph for 8- 10 minutes until the engine reaches operating temperature.
3. Cruise at 55 mph for another 5-6 minutes.
4. Decelerate to 45 mph without using the brakes, and maintain 45 mph for 1 minute.
5. Perform 4 deceleration cycles, without using the brakes, of 25 seconds each where no specific speed is necessary. Returning to 45 mph for 15 seconds in between deceleration cycles.
6. Accelerate to 55 mph and cruise for 2 minutes.
7. Stop the vehicle and idle for 2 minutes with the brake applied and the transmission in Drive (automatic trans.) or Neutral (manual trans.) with the clutch depressed.

The tensioner on the timing chain won't allow any appreciable slack if it were broken. The Gen3 engines had the same timing chain and just had a dampener for the chain to slap against during deceleration, but not have constant tension. The oil pump doesn't really have any parts to wear out and it's always lubricated. Lower pressures at higher mileage is usually due to worn bearings. If the average oil pressures dropped seemingly overnight or during a weather change, I'd be betting on a failed O-ring. I'd repeat the "overfill and incline" O-ring test but on a steeper slope to ensure. Another possibility if the pressure issue was a quick change is a stuck pressure valve in the oil pump. Not saying the oil pump isn't faulty. But, there are other more easily, quickly and cheaply diagnosed and repaired items ahead of it. Just think how you'd react if you replaced the timing chain and still had a hard start, rough operation and P0016 DTC.

IAMDUB,

You have an excellent point on the cam sensor. I got to thinking about that a few days a go as we have a 2002 Jeep Cherokee the kids drove and it would do the hard start and cranking problem, turned out it was the cam sensor.

I am going to change it out this weekend, as you state - a heck of a lot less work. Thank you very much for the manual re-learn steps. I don't have a scanner to recalibrate with. Once replaced I'll give the manual re-leard a try if it doesn't apply then I'll take it to a shop we use and have them do it.

One question on the o-ring, to replace, you have to drop the pan (+timing cover) correct?

Thanks a lot for the feedback. I'll update on this thread the outcome of the cam sensor replacement.

Just the pan

Plimbob said:

IAMDUB,

You have an excellent point on the cam sensor. I got to thinking about that a few days a go as we have a 2002 Jeep Cherokee the kids drove and it would do the hard start and cranking problem, turned out it was the cam sensor.

I am going to change it out this weekend, as you state - a heck of a lot less work. Thank you very much for the manual re-learn steps. I don't have a scanner to recalibrate with. Once replaced I'll give the manual re-leard a try if it doesn't apply then I'll take it to a shop we use and have them do it.

One question on the o-ring, to replace, you have to drop the pan (+timing cover) correct?

Thanks a lot for the feedback. I'll update on this thread the outcome of the cam sensor replacement.

Click to expand...

Just the pan. Use a new gasket and don't forget the RTV at the four seams.

Update - as I expected the sensor won't come out. I got it to turn by spraying Kroil on it. I left it over night and still no go.
I see there are various hacks for removal which mostly involving drilling it and using a lag bolt with a pry tool to remove.
I haven't broken the head off it yet but the tab where the bolt goes thru broke.

I knew it was going to be a PIA process.

Update - well saying the removal of the cam sensor was a PIA is putting it mildly! I drilled a larger hole, screwed a masonry lag bolt into and filled with JB epoxy let set up for 48 hours. Then tried to extract it, used a large pry bar and block of 2x4 as a base for the pry bar. The pressure I was able to put on it with that process did not make any difference, that son of gun will not come out.

I am not down to removing the timing cover to get it out. With the that in mind, what is the best way to hold the HB to remove the bolt? I was going to use a large pair of vise-grips slipped through the opening in the back and up against the AC bracket and use my air impact driver to remove the bolt.

If you are removing the timing cover, just buy a new cover and new cam sensor...
Neither are super expensive and it'll save you a lot of frustration

Plimbob said:

what is the best way to hold the HB to remove the bolt?

Click to expand...

large strap filter wrench
or Ls flexplate flywheel holder