i just got back from a junk yard and i have 3 iat sensors, i went to put a muiltmeter to them to see if they are good. what should it read when i do this?

 

Try this table, it shows resistance values depending on temperature the sensor is reading.

If the values are way out of range, do not use that sensor, it will make your engine run poorly.

Lou

 

ok thanks, now would i put the + and - from the multimeter onto where the sensor plugs into the connector?

 

That's a big 10-4.

Lou

P.S.: Make sure it's set on resistance (either autorange or somewhere in the 20k range).

 

on mine it has 200 2k 200k 20m for ohms

 

Choose the 200k then. At room temperature, e.g. 70 degF, you should be seeing 3.4 kOhms.

Lou

 

ok, thanks very much

 

ok i just tested the four i have, 2 were 3.0, 1 was 2.9, 1 was 2.8. i am in my room temp is close to 70. should i just use one of the 3.0 one's?

 

If you want to make absolutely sure you pick the right one, I'd put them a pot of boiling water for a few minutes and then pull them out one by one and quickly measure the resistance. Then I'd repeat the measurement on all 3 after they've sat in the freezer overnight.

Whichever gives you the best results is your candidate.

Lou

P.S.: For the boiling point, you can switch the multimeter to 2K for better precision (the resistance should be in the 200 Ohm range). For the freezing point, switch back to 200K because you'll be expecting 25Kohm).

 

yeah i did something like that, but i used a lighter, i picked the one that went down and up the fastest.

 

Not necessarily the best way to check them. "Fastest" is no quantification of precision. (no personal offense meant here or anything, I'm just stating facts - I'm not great with words so don't take anything personally, please)

If you want to pick the best one, you would need to check the sensor readings at known temperatures. That way only you can know that it is working accurately enough.

Hope this helps.
Lou

 

[QUOTE=BigBabyLou;3317582]If you want to make absolutely sure you pick the right one, I'd put them a pot of boiling water for a few minutes and then pull them out one by one and quickly measure the resistance. Then I'd repeat the measurement on all 3 after they've sat in the freezer overnight.

Whichever gives you the best results is your candidate.

QUOTE]

so the water won't hurt the sensor any?

 

If we're talking about stock TPI IAT sensor, then no. Cuz those are (unfortunatelly) identical to the CTS sensor which is designed to be immersed in water. It's just a big chunk of metal with a plastic connector on it, that's all. The sensor sees higher temperatures than the boiling point, on a regular basis.

Lou

 

no i am talking about the iat for the tbi

 

Dang, then you actually have the correct sensor! Lucky you.
So in that case, I wouldn't boil them. You could still put them in the freezer and measure, no harm in that. If you were here in Texas, you could just take them outside and read the resistance for 110+ temperatures. But I guess where you're at, you don't get anywhere near 110. Find a place with the highest temp that you can find (sauna??) and measure the senders there.

Sorry, I assumed you had a TPI system, your car being
91 350 and all. Not many 350 TBI engines out there.

Hope this helps.
Lou

 

it gets up to 110 in nebraska not as much as texas though. lol i did have a 305 then swapped in a 350.