2007 4.8 express van with 360k miles. Had it since about 330k. A few weeks ago, I was getting a flashing check engine light on the highway with a little more than cruising load.

Replaced plugs and wires, the plugs were worn out!!! I don't know how it even ran. Been running better than ever. No more flashing light.

On the way to work on the highway yesterday, 40 miles each way, the light started flashing constantly. Less power, missing, etc. Pulling away from the off ramp, its definitely down a cylinder. Get to work, idling, I can see the exhaust steam puffing. Drove home with no issues,running fine, and back and forth again today.

Any ideas?

At first I thought broken valve spring, plug wire not seated, lifter, 02's.....It's running great and appears to have fixed itself.

 

All the boots on good?

 

That motor needs to get its $hit together! With only 360 on the clock. I mean come on!
How bout coil going bad and being intermittently working?

 

Thought so. It did it again on the way to work the day after I posted this. I went out there at lunch. I can only get to 3 wires from under the hood, but I was able to push one in at the coil very slightly, and hasnt acted up since. Pulling the engine cover is an ordeal, and I didnt have the time then or since. There is a reason I don't know which cylinder it is via vcm scanner. If it happens again, I will be able to pull the code......

 

Ha! I have only had it for about 40k or so. It owes me nothing for what I paid for it, and it keeps on going. Could use valve seals, and I am sure springs wouldn't hurt. I have been looking for a replacement (less rusty, less yellow) van for a while. I'll part out the van, but I will keep the engine and trans for who knows what torture purposes.

 

If a LS engine has DOD, the lifters can seize up. My mechanic showed me some that he pulled from a 5.3.