Cowracer
07-12-2004, 06:34
OR: FUN WITH THE IAT PROBE!
Many months ago, I posted a topic about an intermitant loss of power. Some days the truck ran MUCH better than others. No pattern of fuel quality, ambient temps, phase of the moon, or anything else could be found to be causing this. I was convinced that somewhere, some sensor (I termed it the 'x' device) was detuning my truck for whatever reason.
Last week, my truck was an absolute pig towing my boat. This weekend, I started checking things. I eventually removed my intake air temp sensor (IAT) and it was coked up SOLID! The IAT was a solid lump of charcoal, and by the looks of it, has been for some time. I am assuming that the 'themal mass' of the crud on the sensor was really messing with its operation. I ran down to the parts store and got another one post haste.
I started playing around with the new one and found that it reads about 7k ohms when frozen, about 4.5K ohms at 36 degrees and around 2K ohms at 180 degrees. This got me to experimenting...
I wired in a 10K ohm rheostat into the normal IAT sensor plug and ran the wires with the rheostat into the cab. When dialed down to a low ohm setting, the truck made noticeably less power. EGT's were quite a bit higher (due to having to work the engine harder?). When dialed up to a higher ohm setting, the engine brightend up considerably and EGT's dropped somewhat.
Now I know that high IAT's will cause the computer to defuel the motor. But the smoke out of the tailpipe (before the turbo spooled up) appeared to be the same either way. Not a scientific test but still curious anyway. One would think that with less fuel, there would some change in smoke.
Is it possible that the computer adjusts timing based off the IAT?
At any rate, the truck seems to have 'consistant' levels of power now. This makes me happy.
Tim
Many months ago, I posted a topic about an intermitant loss of power. Some days the truck ran MUCH better than others. No pattern of fuel quality, ambient temps, phase of the moon, or anything else could be found to be causing this. I was convinced that somewhere, some sensor (I termed it the 'x' device) was detuning my truck for whatever reason.
Last week, my truck was an absolute pig towing my boat. This weekend, I started checking things. I eventually removed my intake air temp sensor (IAT) and it was coked up SOLID! The IAT was a solid lump of charcoal, and by the looks of it, has been for some time. I am assuming that the 'themal mass' of the crud on the sensor was really messing with its operation. I ran down to the parts store and got another one post haste.
I started playing around with the new one and found that it reads about 7k ohms when frozen, about 4.5K ohms at 36 degrees and around 2K ohms at 180 degrees. This got me to experimenting...
I wired in a 10K ohm rheostat into the normal IAT sensor plug and ran the wires with the rheostat into the cab. When dialed down to a low ohm setting, the truck made noticeably less power. EGT's were quite a bit higher (due to having to work the engine harder?). When dialed up to a higher ohm setting, the engine brightend up considerably and EGT's dropped somewhat.
Now I know that high IAT's will cause the computer to defuel the motor. But the smoke out of the tailpipe (before the turbo spooled up) appeared to be the same either way. Not a scientific test but still curious anyway. One would think that with less fuel, there would some change in smoke.
Is it possible that the computer adjusts timing based off the IAT?
At any rate, the truck seems to have 'consistant' levels of power now. This makes me happy.
Tim