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High intake air Temp

07-11-2011, 03:15 PM
So, 97 Geo metro 4 cylinder... bought it last month with no lights on... but within 7 miles of purchasing it the check engine light came on. Code is for a High Intake Air Temp... went to take a look at the sensor first... but the sensor had just fallen out of it's mount and was sitting in a hotter area than it belonged... I plugged it in where it goes and the light went out... for about a week. The light came back on, the sensor's where it should be, and I have the same code. I figured it being close to the exhaust manifold may have damaged the sensor, so I replaced that... and the light stayed on. Since it was intermittent before, I assumed the code just didn't clear, so I've been driving it for a while hoping the computer will reset, but no luck.

So I'm gonna take it to someone to ask them to clear the code and hope that's all it is.

So, assuming the sensor's fine, what would cause a constant high intake air temp (including when the car first starts)? (Keep in mind I'm near Seattle where 70 degrees is "really hot" even for july)

07-11-2011, 04:29 PM
Hi and welcome to AF!

It seems you've provided a fair number of details, so hopefully someone with more experience working with your make & model can shed some light on this for you!

07-11-2011, 08:55 PM
Thanks for the welcome :)

In case it helps: I got a code reader and reset the light successfully, but the light instantly came back on, so there definitely is something wrong. Took two readings, one when the car first started up and one while driving on the highway:

On start up:
Fuel Sys: CL
Calc load %: 5.1
ECT (degrees C): 92
STFT B1 %: -3.1
CTFT B1 %: 0
MAP (kPa): 32
RPM: 878
Vehicle speed (KM/hour): 0

After a couple of miles on the highway going about 55 MPH:
Fuel Sys: CL
Calc load %: 36.9
ECT (degrees C): 91
STFT B1 %: 3.9
CTFT B1 %: -4.7
MAP (kPa): 73
RPM: 3202
Vehicle speed (KM/hour): 86 (about 55 MPH)

I'm not sure what STFT and CTFT mean, so I don't know why they're going positive and negative all over the place, and I assume the "calc load %" is measuring how hard the engine's working compared to the load it's rated at?

ECT stayed about the same, manifold pressure went up due to speed, which seems logical to me.

I've got no clue where to go from here and I really don't want to take it to a mechanic unprepared. Apparently around here it's gonna cost me at least $100 just for them to get an estimate as to how much they think it'll cost to fix... which I find repulsive.

07-11-2011, 09:55 PM
what code are you getting and the scanner should show the temp that the sensor is seeing. the 92 c degree one is not right, if its the water temp it should be outside temp at startup and warm up as car warms up. if its the air temp sensor its way off on the reading

07-12-2011, 05:55 AM
Was that a hot startup? "Cause your coolant temperature is reading 200 at all times, if the engine was hot the whole time, then that's alright. IF the engine was cold, then you've got multiple problems. Okay, wait a minute, your fuel system is in closed loop operation and your idle is at 878, so that must be a hot start, nevermind.

MAP sensor value doesn't seem right to me, but I'm not sure about the kPa measurement units, need to load up one of my logs and review it to see what kind of numbers I get to compare.

You not only need a good sensor, you need good wiring from the sensor to ground and from the sensor to the PCM. There should be a scanner reading for IAT, which is intake air temperature. As always with a Metro, I'm suspecting a bad ground. The PCM and the sensors all share a ganged ground on the bottom rear of the intake manifold, under the throttle body.

07-12-2011, 06:17 PM
Good point about the hot start thing.... yes, the first test on startup was after I'd drove about 6 miles to the store, then had let it rest for about 30 minutes or so, so it was still pretty warm. I did another test this morning after it had sufficiently cooled down:

Fuel Sys: OL
Calc load %: 9.0
ECT (degrees C): 30 C (about 86 Farenheit although it's maybe 60 degrees today)
STFT B1 %: 0
CTFT B1 %: -0.8
MAP (kPa): 42
RPM: 1197
Vehicle speed (KM/hour): 0

Drove on the highway for miles to pick up the wife and let the car warm up.

Fuel Sys: CL
Calc load %: 5.5
ECT (degrees C): 91
STFT B1 %: -2.3
CTFT B1 %: +2.3
MAP (kPa): 34
RPM: 893
Vehicle speed (KM/hour): 0

So car was parked both times, difference between cold start and after 5 minutes of driving, the fuel system changed from OL to CL, temp went up from about outside air temp to nearly 200 F... and it idled lower with a lower load % after having been run for a few minutes. ... still have no idea what the STFT and CTFT B1 % are.

07-12-2011, 08:05 PM
So.... any ideas at all what physical problems could cause this? Or is it likely that it's 100% electrical?

07-13-2011, 05:21 AM
Short Term Fuel Trim and Long Term Fuel Trim. Never heard a C used there, but that's got to be the same thing. Yes, I definitely think it's electrical, look here first:


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