I have a late model 99 7.3 diesel and have noticed some problems with intermittent power fluctuation while driving. Sometimes the motor sounds muffled, but the noise will get high pitched and it has more power intermittently. This might happen 2 or 3 times up a large hill, and sometimes it doesn't happen at all. The pickup starts and idles well. The noise difference sounds similar to comparing the stock to the 80e tune. The 80e tune sounds higher pitched. I noticed the problem on 80 tow while pulling load. I've logged some operating conditions with my OTC Genysis and would like some opinions on this. Here's what i found:

In park idling @ 675 RPM with the 80 econ tune and oil temp of 194 degrees the icp was 655 psi

In park holding the RPM at 1360 rpm
Stock tune: ICP = 722 psi at 14% duty cycle
80 Econ: ICP = 921 psi at 14% duty cycle
60 tow: icp = 880 psi at 15% duty cycle


Driving up a hill at 1600 rpm on the 80 econ tune, ICP = 1400psi at 21% duty cycle

Full throttle run from 60 to 90 mph

Stock mode – the max duty cycle I saw was 57%, ICP stabilized at 2400 psi – The P1211 code was set

80 econ mode – The duty cycle peaked at 80% at the end of the test, ICP held 2163 psi – the P1211 and P0238 codes were set. Once I stopped I hit the gas and nothing happened, a second later the power kicked in hard and it ran fine all the way home.

I have replaced the fuel filter and pulled the wire off of the ICP and there was no oil in the connector. Any information would be greatly appreciated.