1997 7.3 PSD Barometric Pressure Reading - Rough Idle - PowerStrokeNation : Ford Powerstroke Diesel Forum
 
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post #1 of 6 (permalink) Old 04-03-2017, 12:59 AM Thread Starter
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1997 7.3 PSD Barometric Pressure Reading - Rough Idle

Hi,

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!
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post #2 of 6 (permalink) Old 04-03-2017, 01:05 AM
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Re: 1997 7.3 PSD Barometric Pressure Reading - Rough Idle

Typically doing sensor readings, you should verify with stock settings/no chip.
Also something isn't right here. You're giving us metric readings... but... You're truck wouldn't hardly be running with 2750kpa icp. That's just under 400 psi.


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post #3 of 6 (permalink) Old 04-03-2017, 02:13 AM Thread Starter
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Re: 1997 7.3 PSD Barometric Pressure Reading - Rough Idle

Ok thanks, I will check the readings in stock mode tomorrow. Do you know if I have to uninstall the chip, or can I simply switch it to the stock setting? Sorry I was stuck in Metric mode, I meant 2750 PSI (18960 kPa).
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post #4 of 6 (permalink) Old 04-03-2017, 02:43 AM
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Re: 1997 7.3 PSD Barometric Pressure Reading - Rough Idle

That's not too terrible, Iirc.
I guess you can try the stock tune first to see if it reads right. If it still doesn't, try with it removed.

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1979 chevy c30 dually, sm465, 373's? Converted to 6.2 diesel, pump turned up and advanced a hair.(wrecked)
1994 ford F350 dually 4X4: 7.3 powerstroke, 5 speed. 6637, straight pipe into dual stacks. Cooper discoverer at/3's.
2010 Jetta TDI 40 or so mpg :flippa:
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post #5 of 6 (permalink) Old 04-03-2017, 02:09 PM
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Re: 1997 7.3 PSD Barometric Pressure Reading - Rough Idle

Never assume that "stock" setting really means stock. If you don't want to have to wonder if the chip is a factor, remove it. That's always step 1 anyway.
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post #6 of 6 (permalink) Old 04-03-2017, 06:40 PM Thread Starter
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Re: 1997 7.3 PSD Barometric Pressure Reading - Rough Idle

Alright, I checked on the stock setting.. No change. I'm going to take the chip out after work. I know I need to disconnect the batteries, but other than that can I simply disconnect the chip from the PCM and fire it back up?

Thanks.
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