So I've been having some trouble with the truck lately. Replaced the glowplugs, hi-popped the injectors, did good for a while, but cold starting was very rough, and getting worse, taking longer and longer to pick up the last couple cyls. Then I put the scanner on and got a cylinder #4 contribution code....Oh no, I've lost compression on #4! Thats odd though, these engines normally wash out 7 and 8 first....I'll pull the injectors and have a look. So I went in saturday, pulled all 8 injectors, cleaned em up, reset the pressures back to stock, and decided this was the best time to check the pass side glow plugs. First, I noticed that the wire on #8 had come off, ok, that explains part of the cold start problem, then I looked at #4. Thats odd, there's oil on the threads.....HOLY CRAP, I CAN SEE THE THREADS! Somehow it had backed out of the hole and was hangin on by just a couple threads! pulled it out, cleaned it, tested it and replaced it....tight! Reinstalled the injectors, new return lines and plugs, fired her up...
Man, this truck hasn't idled this smooth as long as I've owned it! The 'whump' noise is gone too, and the power is back where it used to be. Man, I've never seen one of those GPs come unscrewed like that, but since I put them in, I must some how be to blame...too much anti-sieze, or not enough TQ?

Glad to see you finally figured it out!

Maybe too much brown bottle antifreeze? ;)

...Man, this truck hasn't idled this smooth as long as I've owned it! The 'whump' noise is gone too, and the power is back where it used to be. Man, I've never seen one of those GPs come unscrewed like that, but since I put them in, I must some how be to blame...too much anti-sieze, or not enough TQ?
Sounds like the same noise you're complaining about on your truck CR. Better check your glow plugs!):h

ONe of the first things i though about when reading this post, all appears good but the pass side is a little difficult to see. I have no surge as TDG's video, just a very slight miss with intake woofing as if a cylinder is leaking back into the intake. When time permits i will pull the upper plenim and run it to see if its more pronounced. Tough to tell with the turbo sucking but the noise is definately there.

Do you know if it started the same time as you changed the injectors? Another thing I noticed when I had mine out, 2 of the sealing compression washers inside the injectors between the body and the valve had failed allowing the injector body to fill with carbon, no doubt compression had to be leaking there too, so I replaced all 8. Also the outer brass compression washer looked like it was never seated real good, they slid right off of the injectors when I took them out, so I torqued them down a little on the high side @60lb/ft.

I dont think so, IIRC when i bought the truck it was there just ever so slightly, i could never hear it at the intake before but could notice a little babababa... at the exhaust, i doubt anyone else would have noticed it, i could notice it a little more with the 4" install, always thought it to be either a pump or PMD problem just waiting to fail. I have somewhere between 5 - 10k on these hi-pops and this only started to be real noticable after pulling the trailer home a couple of days ago.

Your's being so late of a model, it's hard to imagine what it might be. Too early for the plastic rocker retainers to go, *shouldn't have any valve train/timing chain problems, injectors are fresh, don't suspect PMD/IP at all. hmmm....

I am suspect of all the valve train components including push rods and cam, i drive at 75 MPH daily running 12-13 PSI sustained, when pulling anything i'm sustained @ 15 PSI with spikes to 18-19 PSI.

buy a set of rocker arm keepers, pull the valve covers, pull the rocker arms and pushrods, simple visual inspection will tell you if the components are worn out or not, replace what you need and put the new keepers in. I noticed an improvement in mine just changing the retainers and cleaning the rest up.

Didn't gmctd suggest a compression test over 2 weeks ago?

I can't think of a better alternative to experience, can you?

Any chance the engine problems could be related to the high pressure injectors. That can play havoc on some engines and since this system uses a rather exotic fuel management system. Ain't like anything else on the road. If the glowplug was still in the head, it would still have compression, wouldn't it?

True, but in a gasser engine with a compression leak, air AND fuel is lost.

Diesels - only air - still gets injected fuel shot.

They react differently, most cases.

It did still have most of the compression, when the engine was above idle, it was barely noticeable, but at idle more compression was lost and exxaggerated the surge/miss.