Map Sensor Spiking

boostedmini · Post by **boostedmini** » Mon Aug 06, 2007 6:08 am

Hi All,

I took my mini to the dyno on Saturday just gone for a tune as i have got the intercooler and megajoilt all working.

the Dyno operator and i found that the Map sensor readings were all over the place and were not reading correctly, at idle the Map was around 30 and when coming onto boost it would jump around from 30 to 105 and this was at about 5psi or so.

when the car is idleing it sits at the top of the config box around 20 on the load bin and would jump around.

i used to have the map on a T which suplied vac to booster, vac/boost gauge and blow off valve could this have stuffed the map sensor?

I will connect up and take a screen dump of the Run Time so you can see what i mean.

I have a second unit to try but i need to load the 3.2.1 program in it so if i can fix the current unit i would be happy.

thanks

Grant

Post by **brentp** » Mon Aug 06, 2007 7:19 am

Hi Grant,

I would be very surprised if the map sensor was damaged- these items are normally extremely rugged.

I would suggest the following test before embarking on replacing the sensor:

- use a mechanical vacuum gauge connected to the same location and compare the gauge reading to what you see on the software.
- with the engine off, but MJLJ powered up, and while observing the software: Disconnect the sensor line and manually supply it a source of vacuum and pressure. See if the KPa load indicator changes smoothly. For my testing I use a very large syringe, but something else may work just as well.

Report back what you observe!

boostedmini · Post by **boostedmini** » Wed Aug 08, 2007 12:58 am

Hi Brent,

thanks for the feedback, i have a vac/boost gauge on a different port from the manifold, i will put a T in the line so they are both readings from the same point and see what happends.
I have a mightyvac pump i can apply a vac and pressure to and will let you know.

Grant

boostedmini · Post by **boostedmini** » Fri Aug 24, 2007 3:52 am

OK i have tried a different port on the inlet manifold the same port my vacuum boost gauge is connected too and it spikes all over the place, the vac boost gauge stays still as you could want. i am yet to connect a mighty vac pump to it to test it yet but if the gauge is reading fine then i think the map sensor must be stuffed.

i have another MJ unit to plug in and test too so this will give me an answer for sure.

Grant

boostedmini · Post by **boostedmini** » Fri Sep 07, 2007 4:42 am

HI all,

well i have fixed the MAP sensor problem, it was/is the map sensor, i applied vacuum to the line with ign on and the readings on the MJLJ screen were jumping all over the place.
i then plugged in another MJLJ and upgraded to 3.2.1 and the readings were steady and correct, as soon as ign was switched on the map read 100 and as soon as the car was running the sensor was reading steady as you could want.

so can i buy just a map sensor so i can solder it into my other unit to have as my back up one?

thanks

Grant