It’s been a while since I’ve had time for any forums, but I just wanted to share a recent experience with a customer’s truck that was a first time encounter for me (been a practicing tech for almost 9 years now).

The truck was a 2015 Silverado 1500 5.3 but this could just as easily happen to any of these trucks.

It came to our shop with a hard start/rough running concern. It wouldn’t run for more than about 5-10 seconds at a time regardless of what we tried. During diagnosis we found the #5 cylinder had very low to 0 compression (depending on the position of the piston, it would produce a max of about 30 PSI).

Pulled the valve cover to find the spring for the exhaust valve was broken. There was no other damage to indicate the valve and piston collided, and we confirmed cylinder integrity with a bore scope in the spark plug hole.

Now, this is a known issue that GM addressed in TSB #PIP5423B. And it’s an issue we’ve repaired on other trucks with successful results.

We replaced the spring, keepers and plate, and cranked the engine with the valve cover off to verify normal movement.

Everything looked good, but after reassembly, the truck still wouldn’t start and run for more than a couple of seconds.

Throughout the diagnosis, the only code it would give us is P0106 - MAP sensor performance.

I ran a smoke test on the intake to check for leaks and smoke was rolling out from under the sight shield. It can’t be removed with the intake in the truck, but once I got it out, I found this….





The spring had been broken long enough that the exhaust gases were being pushed back into the intake and melted the runner for the #5 cylinder.

A new intake resolved the hard start problem, but unfortunately, this truck also has some collapsed lifters, so it’s not up and running yet. The customer is still deciding what to do with it.

 

Nice catch - bet most folks would never have found this.