inconsistent MAP reading.....

[jawshnitzel]

ms2 3.0board 2.889code

im having an issue with my MAP reading changing... ive sorted out pretty much every other issue. and reloaded the code a few times. even tried different code versions.. still this same issue.

when the engine is off my MAP allways reads 90kpa.. and this never changes... then i leave the house and go for a tune, get home and now it will read 70kpa. and if i leave it for a while just to sit. i can go back turn the key and it will read the proper 90kpa again... something changes during my drive everytime. and its allways 90kpa then 70kpa. this is with the engine off of course.

i cant explain this difference... have i got a setting somewhere set wrong? or should i be looking into my computer itself more closely??

shnitzel

[kjones6039]

I doubt that it is caused by an incorrect setting. It sounds much more like a restriction in the vacuum line. (ie. kinked hose, smashed metal line or something actually plugging the line)

Under any circumstances it needs to be corrected. You can not reliably tune with that condition.

Ken

[trakkies]

What is the air pressure in your area? Are you very high above sea level? Mine reads 100 kPa with the vacuum disconnected. If it's not reading air pressure with the vacuum disconnected, sort that first before anything else. Did you build the MS yourself?

[jawshnitzel]

a friend built this one. i have built one myself in the past. but his ranger only ran for a month or so before it got put up on stands for a full redo.. so i cant say for sure it was a perfect MS2, but weve both run on it. this is the first we recollect seeing this issue. but the computer hasnt run much really, and maybe had this issue all along. my personal MS has a power supply issue. which most likely has to do with me using an air compressor as a solder sucker.... ya ya, bad idea hindsight for sure.. ha ha... deal with that issue later.

the air pressure is 90kpa here. so, with the car NOT RUNNING it will read 90kpa, ... and when i start tuning it runs awesome. but after a while and after a few good runs i turn the car off to read the current atmospheric kPa and it reads 70 instead of the 90 it read 10 min ago... then if i leave the car turned off for an hour, turn the ignition back on, NOT RUNNING, it reads the proper 90kpa atmospheric pressure again. im up in the rockies. there is definitly no restriction in the vacuum line... i am having this problem with the car NOT running, then of course running too.

another note on the same issue. i calibrated my o2 sensor for the innovate dash gauge. and had it all working nice. exactly matching the megatune readout. THEN!!!! when the atmosheric pressure is reading the WRONG 70kpa, i start it up and my megatune o2 gauge reads wrong. reads different from my dash gauge...

sooooooo, this isnt just the map sensor... im looking at something else thats effecting a few megatune readings..... or im still looking at several issues.. ha ha ha. but i dont think so.

its tune is realy good when the MAP reading is right. drives really well and boost is tuned nice... until something changes...

i have redone all grounds properly, soldered and all to the same spot on the engine head. the only sensor that isnt proper is still the coolant sensor because it is a 1 wire and grounded through the block.

taking a break from it today... maybe a much needed break. hopefully someone can shed more insight. later ill try to get it to datalog this problem. see if it changes while running or if its something that happens only when the ignition is turned off and back on...

shnitzel

[jawshnitzel]

argh... gotta quit playing with this thing for a bit... but i cant!!!! ha ha ha!

thought maybe the issue was me burning new msq files while the car was running. so i went out for several short drives. after each run i would stall the car and look at the kPa level. allways 90kpa. as it should be... so i finally thought i beat the beast.

then i let my naighbor drive the car up town and back with me trying to tune the accell wizard some in the passenger seat... got back home. shut the car down, checked the kPa level.. 70kpa!!!!!!!! sheesh!!!!!!!

thats my update for now. hurting my head.... ha ha ha.

shnitzel

[Matt Cramer]

Is it mounted so the MAP sensor is pointing upwards? If so, make sure it hasn't got any water or oil in it.

[jawshnitzel]

after much playing with it... i started to notice that cabin temperature seemed to effect the problem.... car cold inside, worked great. but if i let it idle long enough for it to warm up inside, then i see the error.

so i brought the MS inside and hooked it to the stimulator. and then ran it while aiming a heat gun at it. sure enough it happened!!! then after its warm enough to show the kPa reading error, i can flex the case a hair and i can make it change.......

ive been looking over and reheating solder joints all morning. havnt found the culprit yet..... still at it. i try to wiggle different things. it seems that just a hair of deflection or pressure on the MS board makes a difference.

bad component????? bad copper trace on board???? my solder joints are all realy good. and ive reheated ANYTHING that seemed could be suspect. but nothing is really suspect...

shnitzel

[jawshnitzel]

well, i took the MS2 out of the car and into the house. put it ont he stim and then heated the circuit board with a heat gun.... sure enough, with just a little heat i had the problem again...

so tonight after lots of looking, we unsoldered the 40 pin chip socket and things were kinda bad underneath. we attempted to solder a new one on and DID solve the map reading problem. but ruined a different pin int he process. so well try to jumper past it and see if we win yet!!!

sooooooo, did find the problem. and created another. ha ha ha... but afterwards we DID fix my other ms2 board, which ended up being a bad D19 zeener. car runs again on my own computer.

thats the update. another problems solved. bad solder joint was the culprit we think.

[jawshnitzel]

both ms2 boards are now running great! jumpered past the bad pins under the 40 pin socket. and past 2 of the gold pins that broke after our many times pulling it out... carefull when doing this, obviously.. ha ha ha...

since then i did a 8 hour drive through very questionable weather. yes we took warm clothes and boots. ha ha... but it made it back great!!!!!! and running tuner studio live analize... isnt that program awesome, come a long way since i played with this 6 years ago..

soo thanx again, MS rules!!! car never ran soo good. and 6psi boost is fun. about ready to hit it with some more!!!!

shnitzel