map sensor
 

i finally found out what is causing my throttle delay while driving in town from a stop.it is my map sensor.i found out by unplugging it and driving the car.i ran over 500 miles with it unplugged and the car runs with no hesitation and is actually faster with it unplugged.HOW IS THIS POSSIBLE ?

im assuming the map sensor is bad sending the ecu a bad signal resulting in making the car run lean and causing a delayed reading.but why would the car run great with it unplugged ? i would think the car would run really crappy with it unplugged.thoughts ?

edit;and yes,the one that sits in the intake manifold

also,can anyone here tell me what the 3 wires coming off the map do.like,which one is ground ect ?

Interesting... looking forward to more details.

That map sensor can get dirty (oil film from PCV), which can make it inaccurate. Try unplugging the sensor from the manifold wiping it clean with a soft cloth, and see if it runs better with it plugged into the ECU again?

already tried that.twice actually.the metal did look like a grayish tarnish like maybe its time to replace it.i would hate to buy a new one only to find out its not it. im just baffled the car runs so well with it unplugged.

edit;also when i was running a modified thermostat,i had very little delay with the map plugged in because the car was running too rich.so it may indeed be time for a new map.car only has 67k miles.

Looking at the MAP sensor (or harness side of the plugin connector), pin 1 is on the left
Pin 1 (Lavender) = +5V sensor power
Pin 2 (Orange) = Sensor signal (1.5-3.8V under vacuum, 3.1-4.8 at atmospheric pressure)
Pin 3 (White) = Ground


See 2009 FSM EC-185-187 and EC-549 (FSM is available for download on this site)

thanks ! repp'd

You're welcome! The FSM is a very valuable download - Nissan 370Z Owners Manual / Service Manuals - Nissan 370Z Forum

PS: The FSM abbreviates colors a little weird. Shown as "L" in the terminal layout, which I assumed was Lavender - turns out it's actually Blue. Go figure.

update;i decided to take the map back out and have a good look inside this time.sprayed some maf cleaner in it and took a tooth pick and pulled out some cotton.im guessing the previous owner had used a cotton swab to clean it :shakes head:..upon further inspection,that greyish material turned out to be some excessive adhesive from when they manufactured it im guessing.

i had a really hard time getting that out off the metal piece that is responsible for the reading to the ecu.anyway,put it back in and plugged it up.i have increased power now down low that i have never had since owning the car.looks like a new one is in the works and thats the problem.what i did, fixed it 98%.

Glad you resolved that. I'd definitely like to learn more about how the MAP factors into the ECU's fueling (and spark and VVEL?) targets.

it can definitely play a factor in throttle delay or bogging on this car.had me thinking it was coolant temps causing my problems. it still seemed faster with it unplugged on the top end but ill know more after i install a new one and give the ecu time to adapt.

Jordo - have you had any luck resolving your random lagging issue?

i'm literally picking at straws at the moment. eyes going crosseyed from analysing datalogs for anything unusual.

what brought me here is i notice in my lagging logs, VACUUM sensor reading seems to hover between 0.9v - 1.1v and this is including foot to the floor.

thing is, i think the vacuum sensor is the brake booster sensor so i'd expect it to be stable-ish

Do you mean the OP? It was his MAP sensor.

My most recent issue was a bad primary O2, but it was causing stumbling at idle and poor MPG, not lagging.

Kenny, can i confirm that it was the sensor on top of the intake manifold that you disconnected?

Did you end up replacing the sensor? How does the car behave now?

MAF sensors get dirty especially with oily air filters over time. I would only spray/clean it with MAF cleaner without touch it with anything.

The e46 M3 also uses MAF sensor and many owners experienced better performance after cleaning it.