iat sensor problem? location?

[tbs1967]

94 ex, 2wd, 4dr. I'm experiencing the following symptoms on warm days (above 60 degrees) when engine at normal operating temperature:
1. Very rough idle ready to stall when stopped. Sometimes it stalls, but most of the times it runs rough.
2. Poor acceleration. But when I reach about 20mph, it runs better but not as smooth.
3. Carbon smell from exhaust.
4. After letting ex sit for 20 - 30 minutes to let it cool down, it starts up fine and runs good until it gets at normal operating temp.
5. Awful fuel milage.

On cool days under 60 deg, I don't have the above symptoms.

I've replaced the following:
Egr valve
Dfpe
Spark plugs
Oil and oil filter
Checked vacuum lines
Checked resistance reading on tps and iac sensor and checks out within specs.

I'm leaning towards the iat sensor based on theory from Haynes manual. But the manual is very vague on the location.

If anyone has had symptoms like mine and the exact location and were able to fix, I would be indebted to you.

 

[FR-425]

It's the coolant temp sensor (ECT) for the PCM (computer)

It is a bad Temp sensor.

http://www.rockauto.com/catalog/moreinfo.php?pk=951148&cc=1119631

Been here, done that already on the 94.

There are (2) sensors, so make sure you change the one that has a cone on the end of it, next to the thermostat housing.

Oh, the AIT is right behind the EGR valve, looks just like a coolant temp sensor. Which is also a possibility on this one. But my money is on the ECT

 

[tbs1967]

Thank you for your feedback. Wouldn't I have a CEL if the ect went bad? Or could the ect be bad enough to cause symptoms and not meet the threshold of the pcm to register a fault?

Autozone has one for $24 and I'll replace it. I wouldn't know if it fixed it until next warm day.

 

[FR-425]

It can produce a 116, 117, and 118.

But I get the feeling on our trucks for some reason it is either not monitored or has to be dead short or open to get a code.

For 118 it has to be above 247 degrees apparent temp/voltage.

For 116 it has to be below -40 degrees apparent temp/voltage.

117 is short to ground.

I think the fault threshold is just to wide on this one.

For normal engine operation you have about a 50 degree window; say 165* - 215* min/max operating temps.