2.9 Pandoras box

[Pix3L8]

Alright, guys, I'm back with a new problem.
some of you might remember that over the summer I rebuilt my 2.9 and have been dealing with issues ever since. since my last post, I have replaced my entire wiring harness, all engine sensors, and swapped around a few ECMs which resulted in a "running" "driving" truck. Sadly the more money I threw at this thing the worst it got, so this past weekend I figured I would do a compression test on the engine (yes I should have done this a LONG time ago). I cranked the engine 3 times per cyl and got 155psi in each with a max of 180 after 5 cranks. Now I was very happy with the results until I got to cyl 1...I got 3-5 psi. I figured maybe I needed to crank it more or maybe there was debris in the spark plug hole which created a leak. no such luck, I cleaned and re-tested with the same results. so long story short I got a little carried away and tore the engine back down in the truck, both heads and intake off etc. I expected to see a damaged valve or piston...nope! both valves were fine and sealed correctly, the piston was fine and the bore was fine. THE ONLY THING I saw was scratching on the surface of the piston. they were spread over the surface and not nessesarilly where the valves are. and like i said the valves are perfectly fine, no damage. the scratches were very shallow and around the center of the piston. I used a feeler and made sure the piston ring was intact, it was, the valves were fine, and the piston wall is looking mint. please for the love of god someone help me understand how I can have 3 psi when seemingly everything is fine. Also, I should mention that cyl 1 is the only one affected by this strange issue.

any help would be much appreciated-Jon

 

[Uncle Gump]

A valve adjusted to tight...

 

[PetroleumJunkie412]

Did you put a cam in it, or take yours out?

 

[Pix3L8]

A valve adjusted to tight...

how can I test this?

 

[Pix3L8]

Did you put a cam in it, or take yours out?

I used the same original cam

 

[Uncle Gump]

There should be a valve adjustment procedure in the service manual.

I myself would listen to what @PetroleumJunkie412 has to say on the subject... he has been all over these 2.9L engines.

 

[PetroleumJunkie412]

I used the same original cam

Interesting. My first guess is a valve hanging open. Or a broken seat.

If not, Gump is probably on to something. Did you re-set your rockers?

 

[Pix3L8]

Interesting. My first guess is a valve hanging open. Or a broken seat.

If not, Gump is probably on to something. Did you re-set your rockers?

well, I did not reset my rockers, just took the head off, rockers off, and took one valve out on cly 1. I was under the impression that I had re-installed everything correctly. I have one more variable, the engine was running extremely rich, so rich that it was fouling plugs and a fine film of unburnt fuel was all over each cyl. not sure if this is unrelated or not. but figured ide throw it out there

 

[PetroleumJunkie412]

Cam installation can lead to all kinds of terrible fun, such as wiping out a lobe, etc. Especially with new lifters.

The other thing is that mine is very fussy on valve adjustment and on pushrod lengths.

Your scratches are very suspicious to me as well. Do you have a photo?

Having one cylinder with no compression tells me a valve is hanging or a seat is messed up, or that you have bad voodoo going on with a ring. Valve trouble starts at the timing chain and can be anywhere from there to the face and seats. Stem guides and seals are always suspect as well.

 

[PetroleumJunkie412]

it was fouling plugs and a fine film of unburnt fuel was all over each cyl. not sure if this is unrelated or not. but figured ide throw it out there

All six, or just #1?

All six tells me your ECM is cranking your fuel due to #1 taking a vacation; if the O2 sees lean at the y-pipe, it will richen up the mix to compensate. If an entire cylinder is down and out, it'll run the other five with enough fuel.for six. (don't ask me how I know this)

Still interested in these scratches

 

[Pix3L8]

All six, or just #1?

All six tells me your ECM is cranking your fuel due to #1 taking a vacation; if the O2 sees lean at the y-pipe, it will richen up the mix to compensate. If an entire cylinder is down and out, it'll run the other five with enough fuel.for six. (don't ask me how I know this)

Still interested in these scratches

all 6 were sooty and I have gone through 3 sets of plugs trying to diagnose this issue (just idling it in the driveway, now I think its something to do with cyl 1 having this 0 compression issue. but the scratches are also very troubling to me as well, like I said I couldn't see any visible damage to any part of the cyl but something definitely made the scratches after I reassembled the engine this summer. the piston did not look like that when it went in. I'm probably going to pull the engine again and just do another teardown, but when I get home this weekend ill look into those valves. I did mess with the exhaust valve on cyl 1 when I tore the engine down the fist time.
ill also note that I replaced the injectors, FPR, fuel filter, all sensors, and the entire ignition system as well as the ICM on the dist. and I can confirm the engine was timed correctly, not to mention I replaced the bearings in the engine as well as a bunch of miscellaneous things along the way.

I never replace the rings because someone had bored the block out .040 and I couldn't find rings that big so I reused the originals.

 

[PetroleumJunkie412]

I never replace the rings because someone had bored the block out .040 and I couldn't find rings that big so I reused the originals.

I'm not a gambler.

But.

If I had to place a bet, I'd bet one of your rings took a vacation.

If not, valve seat.

May want to look into a set of 2.8 pistons if you are tearing down again. If you're overbored that much, they should fit without too much difficulty.

 

[bobbywalter]

piston could be broke.


did you watch the valve events with the covers off? degree wheel and indicator are gold for this.


do a leak down and confirm its air tight closed.

 

[bobbywalter]

we were just talking about the colognes relation to pandora....

 

[PetroleumJunkie412]

we were just talking about the colognes relation to pandora....

Right?? This one is a chin scratcher for me; was hoping you'd jump in.

Guessing a chipped valve seat or a cam lobe took a sh*t. Have seen a few photos of 2.9 cams with a missing lobe, bit that would only make sense if he had no compression release. What's making me curious is light scratching and no compression. That's.. Odd. I like the idea of a cracked/fractured piston though. Would make sense.

My other guess without hearing it is a ring is taking a bath in the oil pan, but without photos or audio, I'm at a loss.