I turned the key and it started right up and idled just fine. There was a strange air sound coming from the exhaust. It sounded like rushing air. So I took it for a test drive. It would go very slowly. When I pressed on the accelerator, it would just blow black smoke out the exhaust, and the turbo boost gauge wouldn't move from zero. I took the oil cap off and felt the air coming out at idle. I could hold the oil cap over the opening and there was enough air coming out to float the cap so it wouldn't rest on the opening.
I decided against buying it. Before I left, I told him I'd go evaluate the numbers and decide later. My mind was saying "no way, you don't want this project", but my heart was saying "I like the truck".
Then I decided to do an internet search for blow-by on that engine. Someone said their engine would run fine with it blowing like a choo-choo train. This didn't seem like THAT much, so I decided I'd try fixing the truck. I figured that if the engine sounded fine and it wasn't burning engine oil at idle, it may just need a turbo.
It was a risky investment, but somehow I ended up buying it and bringing it home. It went 15 mph up hills, and 60 mph down hills.
My first thought was that one of the turbos was bad. So I pulled off the air intake to see the low side turbo. It was spinning at idle. I pulled off the air tube from the high side turbo and snaked my bore-scope camera in there, but couldn't see anything. The high side turbo diagnosis will have to wait. There's a lot more you have to remove to get at the high side turbo.
Next, I verified that the mass air flow meter was functioning with my OBD-II scantool. But I happened to notice that the MAP sensor wasn't varying much. It was hovering around 24-25 in Hg whether the engine was idling, revving, punching the throttle, or even with the key on and engine off. I took the MAP sensor out and used a vacuum pump to verify operation. It was ok, so I cleaned out the carbon buildup and re-installed it.
There were no trouble codes because somebody erased them. You can tell because it records the miles since last reset. An OBD-II trouble code is an excellent diagnostic tool. But don't go and replace the sensor just because the trouble code is coming from that sensor. Sometimes a sensor is bad. Other times, the sensor reads out of range because of another problem. Sometimes multiple sensors give out-of-range readings, throwing many codes because of one simple problem.
The truck's DPF filter was removed and replaced with a DPF delete kit. I think they did this in an attempt to fix the no power problem. The kit came with a programmer that had five levels of performance. Level 5 claimed a 200 horsepower increase. So I plugged in the programmer and it said that the computer was programmed to level 5. Um, ok that's not going to fix it. So I returned it to the stock program. The amount of smoke coming out of the exhaust greatly decreased, but it didn't get much more power. But it would rev higher. I didn't take it out for another test drive because that wouldn't give me any more relevant information for troubleshooting.
I unbolted the turbo's variable vane actuator and moved the unit while the engine was idling. I had the air tube on the turbo's output disconnected. Moving the vane control didn't seem to affect the airflow coming out of the high side.
Finally, I opened up the high side turbo and found that the turbo would not turn by hand. It would rotate with a wrench though. There's my problem. The high side turbo needs to be rebuilt. Just FYI, that nut you see in the center of the turbo is reverse-threaded. Turn clockwise to loosen.
We'll see if a new turbo makes it go.
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