'07 Cummins ISX/Ultra Shift Lost Power After a Service

Truck ran strong for the two weeks I drove it. Then our mechanic did a service...oil change, all new filters, adjusted the brakes, greased, and recharged the AC system.

As I backed the truck out, I knew something was different. Hooked to the trailer and went off to get my load. I couldn't get the truck above 35 mph on flat pavement. Back to the shop I went. Mechanic swapped out the prefilter and looked everything over. Found nothing else wrong. So off to Peterbilt we go. Truck could hardly maintain 60 mph bobtail. Came to a stop facing uphill at a light, but when I went to accelerate, the transmission wouldn't shift out of 2nd gear. I had to put in manual mode to get it to change gear. Out it back in drive and came to a stop at another light. then I got a "F" on the indicator. Engine wouldn't rev. Turned the ignition off for a minute, then restarted and drove the 1 mile to Peterbilt.

Peterbilt of Louisville reprogrammed the transmission and set the idle down to 650 from 750. Truck will get to 60, but I can still feel the lose of power and still hangs up in second gear. Hooked to a trailer, but it won't go over 60. Back to Peterbilt we go. They checked everything as I waited for 6 hours, but they found nothing wrong. The tech even rode shotgun with the laptop hooked into the ECM, but found nothing wrong. The transmission even got hung up in second gear twice, at the same lights, but could offer no explanation.

Off to Cummins Crosspoint in Louisville.

Cummins tech inspected the truck for 30 minutes and thought the engine had a poorly functioning injector. Ended up replacing the #6, ran it on the dyno, then we picked up the truck the next day. Truck feels a little stringer bobtailing, but when hooked to a trailer, getting over 60 takes forever. Back to Cummins we go.

A different tech checked out the truck. Nothing looked odd in the laptop, but he did tell me one thing that I had thought previously. The engine didn't seem to be revving up fast enough. He also said it seemed to be idling a little rough. After some more testing, the service manage mentioned the injectors are running at 16% loo, but should be 9%. This truck will need the other 5 injectors replaced, but they were not causing the power loss. They also checked for air leaks, but didn't find any.

He also mentioned that this engine is set to not come in to full power unless it is loaded (I don't remember the term he used). He said he could put the power into direct which will give me all 450 hp anytime I wanted, but would cost $350 and would probably reduce fuel mileage. But this engine always felt strong before the service.

So we decided that I try it out with a loaded trailer and I'll report back. As I was leaving, the tech mentioned that he thought something was wrong, but wasn't really sure what it could be.

The engine does feel stronger with the new injector, but doesn't feel any stronger at 60 mph with a empty trailer.

Fuel filters were changed multiple times and the #6 injector was the only repairs. Boost and fuel pressure is normal. I'm not sure what else to look for. Could something with the Ultra Shift Transmission cause this? ECM is reads 450 hp and 1650 tq on the laptop, but it doesn't feel like it. If the ECM is reading full power, then why would the guy in service tell me full power won't come on until the trailer is loaded?

No brake drums feel hot.

I know I have a small coolant leak. Added 1/2 gallon the first week of driving. Just added 2 gallons due to the sweet smell of antifreeze that reminded me to check it as I got home, but this is the first time I ever smelled antifreeze from inside the cab. The last few days it was just a slight smell after I climbed out of the cab.

Everyone keeps hating on my Ultra Shift Transmission

I have a feeling I will eventually find the problem and it will be the smallest thing in the world.

Any clues?

 

I noticed a puddle of antifreeze under the truck this morning. The wet path leads up to the cylinder head.

 

I think found the problem. It was only a bad ground at the batteries from the ECM. Seems to pulll much better. I'll have to wait and see what it does tomorrow.

It wasn't much fun trying to drive the WV and MD mountains at 15 mph

 

The UltraShift is designed around a properly running engine. I would love to get into the ECM. I would like the clutch to engage sooner, start in a higher gear, and to be able to manually change gears at any rpm. Sometimes, at full throttle and 80k, the engine is running 1300 rpms in 10th gear, but the transmission won't downshift. I'd like the transmission to downshift at 1400.

 

Still having power issues. Laying in the bunk, I notice the engine idles much rougher then usual. Previously, the idle was very smooth. Every time the air dryer farts, the engine idles rougher for a few seconds.

 

Which clutch? The transmission. I idle in neutral

I can rev the engine and hear the weights in the clutch move, but this thread is about my power problem.