Preliminary results. The difference in readings between the old MAP sensor and the new MAP sensor is approx 1.5 inHg (5 kPa). Pretty much exactly the amount the old MAP was skewed from age.
Other than having the constant offset, the old MAP sensor was responding and working perfectly. It gave nearly the exact same volt / pressure curve as the new one.
As expected, the whole set of trends for both the STFT and LTFT have shifted up by at least 5% to 7%. No longer as far -ve. With occasional +ve FT occurring now. Have to get some more runtime on it to see where it settles out. Then I can summarize some notes here.

On the question of manifold pressure/vacuum at idle. At idle speed 620 rpm. The vacuum gauge reads 18 inHg when plugged into the brake booster tap port.

 

That isn't adding up for me, can you clear it up? You reported 34kpa at idle prior, which is about 10inHG. 18inHG is about 61kpa. Is the obd reporting 61kpa at idle with the new MAP sensor? I would expect the vac gauge to read same.

 

Sure fj5gtx. To clear up the MAP vs VAC.
It appears to me that you are reading the MAP and interpreting it directly as a vacuum gauge.
"Gauge" is a measure of pressure relative atmospheric condition present. Gauge can be pressure or vacuum.
The MAP is not a gauge. The MAP is absolute air pressure.
A MAP reading of 34 kPa is not 34 kPa gauge vacuum.
To get "gauge" you must subtract the atmospheric pressure from the absolute pressure.

Subtract the station barometer pressure from the MAP pressure to get the gauge pressure of what is in the manifold.

For example:
If barometer at location is 100 kPa,
and MAP sensor value is 34 kPa,
Then the pressure in the manifold is 34 - 100 = - 66 kPa, since the result is negative this is vacuum. If it were positive, it would be boost.

Observed conditions today were 92.1 kPa barometer pressure.
At idle, 620 rpm, the vacuum gauge connected to the brake booster reads -17.5 to -18 inHg ( -61 kPa).
The OBD MAP reading of the new sensor at same time was 32 kPa.
The new MAP is therefore indicating 32 - 92.1= -60 kPa ( 17.7 inHg ) vacuum.

 

I see the disconnect. TorquePro has a vac gauge (among others) on its basic screen. I just use that initial screen to see the vac at idle then watch it when I blip the throttle. Then I end up scrolling off to the right to add the fuel trims and timing advance. I'd only pull more pids if I saw something looking wrong. I've assumed that Vac gauge is using the MAP sensor, so I basically equate the two - and I've got the vac ouija chart that I shared in my mind when I'm looking at vac. That is why I was so confused when you were calculating vac!

 

My scan tool, BlueDriver, gives the MAP reading. It looks like perhaps the TorquePro is doing the math in the background for you in order to display a vacuum value? Can the TorquePro display the actual MAP PID? It would be a good direct comparison if you are able to see MAP, the VAC, and ambient barometer side by side on the TorquPro screen.

Btw, the truck here is running great. Not that there were problems at all before, other than failed B1S2 O2 sensor. I had some time available to tinker with the truck. The intent was to make what was already good to better if possible and maybe learn something along the way. Thank you for pointing me at the MAP. As I dug into it I learned a lot. The exercise was more value to me than the change out of the part.

The point made by HeyYou about the fuel going open-loop in the upper throttle range was enlightening, and significant. If the MAP sensor is inaccurate that will have a direct effect on fuel economy and power when there is a load on. I wonder why it is not programmed to stay closed loop all the time? I have established that the old MAP sensor was skewed resulting in a rich mix, which the O2 were picking up and cutting back via the fuel trims. In open loop, it would have always been rich - by quite a bit based on the data collected. In the end; from checking and replacing the MAP sensor and verifying the new one before installing, I expect and hope to see much better fuel economy in the upper throttle/load range when pulling the trailer(s) and hilly terrain. In the down low casual drives around town I do not expect to see much different as the O2 - fuel trims are effective at correcting when in closed loop.

Thanks, have a great day.

 

I don't remember if I've actually tried to pull the MAP pid to create a chart in TorquePro. I don't think I've ever replaced a MAP sensor. I'm sure that PID is probably in there. Perhaps TorquePro can read your bluedriver... Torque is the free version, Pro is $5. I bought an ELM327 for $12... so I've got $17 invested into it.

My use is pretty limited on the available features... Prior to using TorquePro, I'd hook up my manual gauge and see if the vac signal looks wrong at idle and throttle blip. Then I'll move to pulling the LTFTs, o2s, temp, and spark advance. If all looks good, I'm done. Otherwise it goes specific to what isn't looking good. Factory spent a pile of time tuning the drivetrain, I like to keep mine in factory specs. TorquePro showing me vac saves me the hassle of hooking up the manual vac gauge.... that is probably at least 10-20 minutes of fooling around, which is now quickly avoided.

I've seen someone have a closed/open loop display in a obd tool before on a video, so you can see the threshold state changes. Pretty sure its one of the 1st videos authors I suggested you look at. Don't know if that is special to the software, or just a PID on some vehicles. I tend to look for conditions where spark advance abruptly changes, which indicates things are not going as planned.... usually pre-detonation, excessive gaps on plugs, or some other ecu related mitigation issue.

I know you think injector cleaner is snake oil, but I've had success really turning around the performance of, new to me, used cars with Lucas treatments. Once cleaned up, I just run a treatment a couple times year - and I don't really notice a much improvement after I've run through an initial thorough cleaning - which is what maintenance is all about. I usually buy a large jug of the Lucas ($20 or less with AdvanceAuto discounts) and it'll last me a couple years with the fleet.

Lots of factors are key to efficient performance. usually the ones I'm watching are:

• factory fuel trims with very minor adjustments
• no retarding of the spark advance profile
• properly operating o2 sensors
• clean injectors

HeyYou knows his stuff; always a great person to have contributing to your thread