'05 D/Max, low compression in 2 cyls, Got any ideas?

[truck_n]

I was trailering up a hill with my 2005 D/Max when I experienced first a ticking sound, then some detonation and black smoke, then all was quiet and everything seemed to run fine except for a distinct lack of power. All this took place over about 10 seconds. I couldn't stop on the hill so I continued to the top. The truck ran fine, but felt like it was running on 7 cyls. I thought it was possibly an injector. By the time I got it too a tech for diagnosis (about a half an hour of driving time) I noticed the oil pressure was dropping.
At first, after diagnostics, the tech said 2 injectors were bad, then he took a compression check and #1 & #3 cyls tested 150 lbs compression while all of the others are at 400 lbs.
I have 230,00 miles on the truck and it has run flawlessly. The shop I have it at is inexperienced in Diesels. My alternative is a dealer, but I thought I would throw it out if anyone could help or had some ideas. You all involved in this forum came through for me on my 2001 with the injector problems, so does anyone have any ideas? Thanks

[More Power]

Remove the oil filler cap, then start the engine. If there is a lot of white smoke exiting the oil filler tube, you have one or more bad pistons. A leaking injector can cause a bad piston.

Bummer!

Jim

[JohnC]

Maybe the head gasket blew between 1 and 3?

[DmaxMaverick]

Adjacent cylinders with low compression most often indicate a head gasket or head issue. Rarely is it the block or rotating assy. Of course, it could happen, but it's not the usual suspect. Before pulling heads, you'll need to do a compression and leakdown test on each cylinder (very easy and quick), while monitoring the other, to determine if this is the reason. I think you'll find the cylinders are sharing compression.

[madmatt]

yep, do a cylinder leakdown and see where the preesure is going before going any farther. into the crankcase=bad times. leaking into the adjacent cylinder = still bad but not as much on the wallet as into the crankcase.

[truck_n]

Sorry it's been a while, but here is the answer. I did take it to a dealer and after the proper diagnoses, he found it had a broken rocker shaft on 2 & 4 cyls. It seemed the other shop mixed up the left and right banks, didn't read the computer right, etc.etc. and thoroughly blew the call.
In any case, one rocker shaft bolt was completely backed out and, according to the tech, probably caused the shaft to break. Fortunately no other damage. The head was fixed without removing it but I had to wait over 2 weeks for all of the parts from Isuzu. We changed all of the rockers, pushrods, bolts, etc. on those 2 cylinders to be safe. The truck runs great again. The wallet is severly damaged though.

Just out of curiosity, has anyone heard of a rocker shaft breakage problem?? The tech said he has never heard of one with that problem. In any case, thanks for all your help.
Tony

[madmatt]

nope never seen that before.