IAT noise or ground issue

[glowryder]

It seems like all of the sudden my setup has gone to pot..
Out of no where, i start seeing my IAT's spike downward. idle, cruise, even the car off, the iats are stable, then a 10 degree drop, then back to ambient. I als see it sometime correlate to the tps changing (Ie going from 0% to X%), but this is only some times. All grounds for the sensor go to MS grounds on the fire wall. I changed nothing, now all the sudden this crap. First my Voltage regulator shits out , now this magical spike..

Ive tried a new sensor, no help. It seems to really act funny sometimes at a cold start. the ambient air wil be around 70 or 80 degrees, and it will swing from 60 to 80 or so quickly for a few seconds, then boom, sits where it should.


Green line on the 3rd data set down is MAT. You can see at start up IATS are all over the place then they figure life out.

[AlexLTDLX]

Sometimes a bit of corrosion or something can crop up. Did you say your sensors are grounded to the firewall? They should be grounded to the sensor ground pin on the MS connector - nowhere else. Some little bit of addition resistance could've crept in, and now you're seeing a differential and noise on the sensors.

[glowryder]

yea i was going over the scematic today, and saw that. I wired this some time ago when MS2E was the big deal. I have since switched to MS3X. Ill have to move those grounds over to pin 7.

[glowryder]

Back from the dead. Looking at my main harness, Pin 7 is like a shielded wire ground, so Im guessing its an older MS2 harness. At the time, the diagram says to wire all sensor gorunds together, which I have done. But I still see some "noise" or erratic readings from only the IAT. The coolant and TPS seem solid. All grounds to the same place . Seems really really odd. IAT is right after Intercooler... Im starting to loose faith its actually a ground issue. IDK.