2.5 feels like it's fighting itself

[holyford86]

I just went and rebuilt a 2.5 for a friend of mine. It's in a 98 with a 5 speed transmission. He ran through some water with it and hydrolocked the motor, breaking the #2 rod and bending the #3 rod. He drove it home, a total of about 1.5 miles, and then moved it around a bit, totaling about another 1.5 miles. there was no internal damage to the motor other than the bent and broken rods and a couple of cracked valve seats.

Went through and replaced the 2 bent rods with new pistons and rods. Replaced the head with a new one, went and replaced all of the rings and replaced the rod bearings as well. Replaced the head, all gaskets, and did a tuneup as well.

The engine starts and runs fine for about 10 minutes, with no noise, then the engine just surges a few times, starts knocking loudly, seemingly through the valvetrain, and dies, almost like it locked up. Then with no wait at all, you can crank it up and it runs fine for about the same amount of time and dies again, with the same result. It will do this over and over again. Watching the live data on my code reader shows me that the calculated engine load goes from about 35% up to about 51% then it dies, It starts surging at about 49% calculated load. All other sensor values show up as normal, and the computer shows no codes, and the check engine light does not come on.

It almost seems to me like a plugged catalytic converter, I have no firsthand experience with this but it's the only thing that I can think of. The truck has about 170k on the clock

 

[Duane867]

I would have been clogged up before the rebuild then I would think.
Ask the owner if it had a bad cat to start. If the exhaust was banged around real good and the cat was jared hard enough ( say bounced off the concrete ) it could break up things in there and clog it up.
Have you checked the timing yet ?
Vacuum lines ? Checked the new head gasket for leaks ?

 

[12step]

drop the exhaust ,and try again. This will take the cat out of equation you will get a cat efficentcy code ,but the engine should still run fine.

 

[holyford86]

-Update-

The aforementioned problems seem to have disappeared. Let the truck run for a good hour today with no issues whatsoever. It seems that a good cool down cycle may have helped it. I'll keep you updated.

 

[Duane867]

Some times you just have to run the gunk out of it after a rebuild.
Dont forget to change your oil as soon as possible....