I'm having an issue with rough idle on my 1997 7.3 PSD
. It's not a violent rough idle, and the engine sounds normal but it vibrates the truck a bit. I've checked codes with an OBDII scan tool and FORscan, no codes. I've checked several instrument readings, and thought the barometric pressure reading might be suspect. I'm in Vancouver, right beside the ocean so I would expect 101 kPa however the reading is 64.3 kPa. The truck has the external BARO
sensor under the dash, so I disconnected it thinking the PCM
would default to 100 kPa but instead defaulted to 60 kPa. Out of curiosity I looked at the EBP
sensor reading with the engine off and it read 100.2 kPa which is about right. I recently went up north to Prince George (600 Meter elevation) and the BARO
pressure reading dropped from 64 to 60.3 kPa, so it is measuring pressure but appears to be off by about 40 kPa. I'm wondering if the previous owner could have programmed an offset factor somehow seeing as it defaults to 60 kPa? Or maybe the PCM
is bad. Just dawned on my, it has a TS 6 position chip, so maybe that could change the PCM
readings? It was set to +70HP when I read all of the parameters, I will go check it again on the stock setting.
From what I've read the PCM
will retard the injection timing according to the BARO
pressure, and I would imagine with would decrease the HPOP
pressure for a leaner air fuel mixture (I'm just guessing here, might be way off). I have an analogue gauge on my dash for the HPOP
pressure, and on the highway in 5th gear doing 100 km/h when I step on it the pressure only goes up to 2750 kPa and it just feels like it's lacking power. Still lots of power at the bottom end though.
The truck has 250,000 km on it, and the engine was replaced by the last owner which came out of a California 97 E350 with ~70,000 km. It seems to be in good shape.. Starts fast, doesn't smoke, doesn't burn oil. Just seems to me like the timing is slightly off.
Any opinions / tips would be much appreciated. Thanks!