I gave my car in perfect running condition to a tint shop to have the window tint changed. When I got the car back, it was running horribly (super rich with almost no power). After changing the fuel injectors and spark plugs with no improvement, I used a timing light to see that the timing was super advanced. Checked the timing marks, and the crank pulley was behind by two teeth. Compression check was okay before I checked the timing marks, so I know there was no piston to valve contact. I set the timing up and blipped the starter to make sure everything was okay. Like a total moron, I forgot to put the timing key back in. Leak down shows 40% leak on cylinder 6 to the intake valves. Not the worst, and it runs better than I thought it would. About a 30hp loss according to butt dyno. Cylinder 6 still makes about 100psi on compression test, so I'll keep driving it for now.

My dilemma is wondering why the timing belt jumped. The shop seems honest and I don't believe they abused it. Even if they did, I don't see how it would jump time, as I abuse it daily without issue. The timing belt, tensioner, water pump, tensioner pulley, and idler pulley were all new with about 1k miles. I've been driving it for a couple hundred miles after fixing the timing, and the same tensioner is still strong. Any recommendations to prevent it from jumping again?

 

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Oh man. I see it in your signature that it says 'J36'; however, I don't want to believe it's the beauty above? And this is the one you adapted a M90 to?

I'm just making 'noise' here so forgive me if it fly's in the face of absurd. As you know, it's rather slow on this side of the forum, so hopefully you get more response then mine.

Other than the obvious momentary tensioner fail, could repeated long, high rev pulls, in more likely the lower 2nd gear, rather than say 3rd, for instance, and then a sudden (total) lift off the gas cause a T belt jump /skip?

I mean, if one wanted to abuse a manual S/C'ed J-series on local streets, during a short run around the block, that might be all you could get the car up to in speed. See what I'm saying? You know how some other high performance cars 'pop' the exhaust, during long decelerations, too sound cool?

Maybe you have modification plans for the J35A3 now?