Honda MAP sensor problem

[driv3r0000]

After loading a base map and setup a wideband o2 I checked my fuel map and the MAP sensor is reading at the top of the map as if it's wide open throttle with the key on engine off. I have a 93 prelude using a 30-1001. The MAP sensor is stock.

I started the car and it's dumping fuel and stalling out. All the MAP sensor settings are untouched from the base cal provided. The parameter box for MAP voltage reads about 2.5v give or take with engine off and key on.

Is there some setting that's wrong or what could cause this?

[SB]

First check the wiring to your MAP sensor. If the sensor is not connected to the EMS properly, or the software is not configured to use the MAP sensor properly, the EMS will use throttle position as load (like a limp-home mode).


If you don't find an obvious wiring problem, then it's time to log some data. Please perform these tests with the engine off.

1.) Open AEMPro, connect to the EMS and open the Tuning template (Templates >>Tuning)
2.) Unlock the parameters window (click the "Locked" label at the top-left corner)
3.) Click the bottom (blank) box and select "MAP Volts" from the menu.
4.) Another blank box will appear at the bottom. Click it and select "MAP as Load."
5.) Another blank box will appear at the bottom. Click it and select "MAF Volts"
6.) Another blank box will appear at the bottom. Click it and select "TPS Volts."   
"Engine Load" should already be displayed in the parameters window. If not, please add it also.   

7.) Hit the [F6] key to begin datalogging. Unplug the vacuum line to the MAP sensor and blow some compressed air at the map sensor (don't get the air nozzle too close to the sensor or it may be damaged), we're looking to see the MAP voltage to change in response to the air pressure the sensor is seeing. Hit the [F6] key and save this datalog, please label it step7.stf.

8.) Hit the [F6] key to begin datalogging. Unplug the MAP sensor then plug it back in, we're looking to see the MAP voltage change when it is unplugged. Hit the [F6] key again and save this datalog  (step8.stf). 


9.) Hit the [F6] key to begin datalogging. Press the throttle a few times, all the way full throttle then back to zero,  we're looking to see the TPS voltage change but want to make sure the Engine Load isn't changing and the MAP voltage isn't changing either. Hit the [F6] key again and save this datalog (step9.stf).
 

Attach those log files here if you need help deciphering them. Like any datalog viewer software, AEMLog can take a while to get used to.
 


A few other people have logged this data while troubleshooting their cars. For instance, user "dapump2003," their sensor was wired correctly but software was not configured to use the MAP sensor for engine load (using firmware v1.11). You can see his datalogs here for an example...
http://forum.aempower.com/forum/index.php/topic,22658.0.html

[driv3r0000]

All the MAP sensor wiring is stock and was never tampered with so I just checked voltages and continuity. The 5 Volt line is good 5.03V. Ground looks good too. I compared sensor output at the the MAP sensor plug while plugged in to what the parameter says and: MAP volts in AEMpro is 2.87v and at the sensor it's 2.88v

I logged everything and you'll find the files below.

[SB]

Those logs are good...


in the step7 log, you can see the Engine Load is about 100kPa   (atmospheric pressure)  with the engine off, then a bit more when you blow compressed air at the sensor. If you could somehow apply vacuum to the sensor (hand-operated vacuum pump or manual brake bleeder) it should measure less than atmospheric.


In the step8 log, you can see that the MAP volts goes to about 5V when you disconnected the sensor, then back to about 2.8V when the sensor is plugged in.  When the sensor goes to 5V, the Engine Load drops to about 5-15kPa  which is the result of the way the TPS-to-Load table is configured in your calibration (if the MAP voltage is too high it will generate a simulated Engine Load using the TPS sensor). 5-15kPa is a bit lower than most cars will idle at with zero throttle but that's splitting hairs for now.


In the step9 log, you can see that Engine Load remains constant when the throttle changes, this is just another way of double-checking that the EMS is using the MAP sensor for its Engine Load calculation as opposed to the Throttle Position sensor.




Long story short, your logs show that your MAP sensor appears to be wired correctly, your EMS calibration is using it to calculate Engine Load,  and it appears to be pretty accurate around atmospheric pressure which is a good indication that it's likely to be accurate at other pressures as well.


If the EMS is referencing the top row of the fuel map with the key on and engine off, that's probably because the top row is configured to be about 100kPa. The trace should move down to the vacuum cells when the engine is idling.

Are you using aftermarket injectors? If so, you'll need to decrease the pulsewidths compared if you're starting with a base map that was tuned on a stock engine with stock injectors.

[driv3r0000]

We'll it's been a while and I wanted to post the fruit of all my adventures.

To sum up I have an H22 engine that has a fully built head (skunk2 Pro1 cams) stock bottom end. Hytech exhaust and AEM intake.

After a very long email conversation with the AEM tech's I discarded my previous calibration that the tuning shop had done to start over with the factory start up CAL provided with AEMpro.

I setup my wideband O2 and started the car. The engine would not idle due to flooding. AFR's over 10. I discovered that the reason my engine was sputtering and missing was NOT due to cam/crank sensors. It was due to the MAP sensor being improperly setup. The tuning shop had changed it from "MAP voltage" to "MAP as load" which is incorrect in my application.

I also discussed on the AEM forums that the reason my map load was at the top of the map while the engine was off was very simply because the MAP sensor is reading the ambient atmospheric pressure which is about 100kpa. Makes sense. After figuring this out I started the engine and watched the load drop to the middle of the map range as it was running. I then leaned out the fuel in those cells until the engine was idling. I tweaked the idle on/off TPS values from 3.12% to 6.5% (the idle was surging due to the TPS sensor occasionally flickering up to 6%) and now it idles happily at about 1000rpm. I also was able to sync the timing. AND one more thing...no missing or shuddering!!!!!

So I guess my question here is: Since I have race cams the engine is drawing more air and thus lowering the amount of vacuum on the MAP sensor line, and that is why the load only drops to about the middle of the fuel map, yes?

I guess now all I need is some tuning.