Multiple Misfires, No Compression (1 Viewer)

[CapsFanChris]

Okay, so my mechanic friend was helping me with my 2006 GX470 (190k mi). We agreed that he would do the CV axles and that was fine. I needed the water pump (leaking a lot) and timing belt (way past due) changed. He suggested that we tear it down to the head gasket and get the heads cleaned up. I agreed and now I am wishing I hadn't. We ran into one issue after another with wrong sized hardware, the machine shop losing a piece and a number of other minor setbacks. Well, he finally gets it together and fires it up for the first time and it is misfiring a ton. He did a compression test and the right side all was nice and strong (160+/-). The left side however, 0, 0, 30 and 120. Brand new head gasket torqued down to factory specs. The head was pressure tested and the valve seats were done and everything was cleaned up. I am at a loss as to what the issue might be. I am adding pictures of the timing belt and want to know if that looks right. I really don't want to rebuild the head if I can afford it. I suppose it could be burnt valves, but I would have thought the machine shop would have caught that.
Please take a look at these pictures and let me know if you think the timing is off. I suspect that if it is, the valves may have been bent but it seems odd that it would only do that on one side. Any ideas would be appreciated as I really want my truck back!

 

[Rednexus]

The most likely culprit is that the valve timing is off somehow, which would explain very low compression on on side (valves are open on the compression stroke). I am not sure if it would be do to the timing belt being installed wrong; it could also be one of the cams being installed wrong and out of time as well (as the intake and exhaust cams have a geared connection so it's totally possible the cams aren't indexed properly).

If it was my rig I'd tear the front off again and double-check that the belt and cams are indexed and timed correctly. You can also check for compression as you go by turning the engine over by hand and checking that each cylinder has compression when it's at TDC on the compression stroke. You can do that by taping off the top of the spark plug tubes and waiting for compression to pop the tape off. I would go through all 8 pistons.

I don't think you bent the valves as my understanding is that the 2UZ is only an interference engine if the VVTI system is activated. Nevertheless, you can check for valve/piston contact by dropping an inspection camera into the spark plug holes and looking for valve-shape indentations on the tops of the pistons. If they did contact, you should see the marks.

I'd also recommend posting this over on the 100 series forum, there are a few 2UZ experts over there that should be able to help.

Not to rub salt in the wound, but there should be no reason to pull the heads for a refresh. These engines routinely go 300K, 500K, or miles more without having any valve- or head-related problems.

 

[eL PeReZ eSe]

So, I'm working on same issue on mine after changing the camshaft seals. Took the valve cover off and intake cam sprocket was completely loose and with no bolts. yes, I did torque the bolts to specs. nothing broken or off at least. So, loctite on new bolts and hopefully that resolve the problem.

 

[CapsFanChris]

The most likely culprit is that the valve timing is off somehow, which would explain very low compression on on side (valves are open on the compression stroke). I am not sure if it would be do to the timing belt being installed wrong; it could also be one of the cams being installed wrong and out of time as well (as the intake and exhaust cams have a geared connection so it's totally possible the cams aren't indexed properly).

If it was my rig I'd tear the front off again and double-check that the belt and cams are indexed and timed correctly. You can also check for compression as you go by turning the engine over by hand and checking that each cylinder has compression when it's at TDC on the compression stroke. You can do that by taping off the top of the spark plug tubes and waiting for compression to pop the tape off. I would go through all 8 pistons.

I don't think you bent the valves as my understanding is that the 2UZ is only an interference engine if the VVTI system is activated. Nevertheless, you can check for valve/piston contact by dropping an inspection camera into the spark plug holes and looking for valve-shape indentations on the tops of the pistons. If they did contact, you should see the marks.

I'd also recommend posting this over on the 100 series forum, there are a few 2UZ experts over there that should be able to help.

Not to rub salt in the wound, but there should be no reason to pull the heads for a refresh. These engines routinely go 300K, 500K, or miles more without having any valve- or head-related problems.

Honestly, that was his idea. I kind of felt the same way but what is done is done. Thanks for the ideas and I will get it posted in the 100 series section to get additional input.

 

[white_lx]

Regarding your timing pictures. Once you turn the engine over, you can no longer use the marks on the belt to determine if the timing is correct. There are marks on the crank and cam pulleys to check the timing. Typically they have a small amount of paint marker from the factory. Your pictures are not at TDC, which is how you check the timing.

 

[CapsFanChris]

Regarding your timing pictures. Once you turn the engine over, you can no longer use the marks on the belt to determine if the timing is correct. There are marks on the crank and cam pulleys to check the timing. Typically they have a small amount of paint marker from the factory. Your pictures are not at TDC, which is how you check the timing.

Thank you. He is out of town until Monday so hopefully we can get it sorted when he gets back.

 

[CapsFanChris]

This is not a new photo, but one from when the belt was originally installed. Hopefully he can put it TDC and shoot me another picture. It really sounds like a timing issue to me.

 

[white_lx]

In the picture above, the cam's are timed correctly to each other. However, I can not make out the little divot on the crank. Since L&R cams are timed correctly wrt to each other, one would expect similar compression readings L&R.

One other thing to note is that for the VVTi engines, the camshaft gears need to be locked with a small screw before removing. After cam shaft re-installation that screw is then removed. I hope your mechanic friend was aware of that.