Need Help Diagnosing Misfire :( (1 Viewer)

[GTV]

Zero progress. There’s really no sense digging into it until I have an appropriate place to do so. At this point I’m expecting to be out for the season.

 

[Catlin]

Let me add to this thread. I have been working on a friend's 2006 GX470, a VVTI 4.7 engine, with him. We did a timing belt and cam seal replacement on it. Got it back together and it ran but had codes 300,301 and 306 immediately. Compression in # 1 cylinder was near zero. We bent the valves in that cylinder. Here's how I think it happened. To remove the cams, a service bolt has to be installed in the exhaust cam before removal. However, the LH bolt hole for it at #1 top dead center is located at the lower point and one has to rotate the cams to access that hole. We did that with the timing belt off and #1 at TDC. Big mistake, because this caused the valves (intake in our case, I think) to hit the top of #1. The manual just says to rotate the cams to install the bolt, not warning about the dangers of doing that. We thought the contact was no big deal, because we were turning the cams gently. Wrong. The valves are most sensitive.

One way to get that side's service bolt installed is to leave the timing belt on, rotate the cams to access the hole, and put in a short bolt (like 15-20mm) with a thin head. This will clear the internal space and let you rotate the engine back to TDC. Then you can remove the timing belt and those cams safely and not harm the valves. The RH side service bolt is accessible, and I don't recall that any rotation was necessary. Our #6 cylinder seemed to have good compression, but that mattered little.

We thought about removing the left side head to repair the valves, but it looks like the engine has to be pulled out to do that. That's more than we care to do. We live and learn.