Ive got an 89 LO3 and on the passengers side of the motor theres a small electrical plug just sitting there. It's oval and has two wires. I cant figure out what it plugs into. I got the car with an open air element on it and the swap wasnt quite done right since I was throwing codes 23 and 32. I just got a new Air temp sensor and mounted it inside the air cleaner, but that runs off vacuum not electric like I thought it would (the vaccum source was plugged at the TB)
Everything else in the motor bay is still present (emissions, smog, a/c, etc) and everything is functional, So I would think this plug goes somewhere into the stock air cleaner assembly, but to what? The lead on it isnt too long and only reaches the middle of the intake manifold, maybe the middle of #4 cyl at best. Anyone got any ideas on what this is for?

 

Can you snap a picture of it?

IT sounds like there are more issues going on here. I have NEVER heard of a vacume air temp sensor.

 

Sounds like you replaced the thermo-vacuum switch. That controls the pre-heat door on the stock air cleaner snorkel.

You need the intake air temperature (IAT) sensor. That would be for the ECM and take care of the code 23.

RBob.

 

It's a plug to the air temp. sensor that was in your factory air cleaner. If you still don't have the original air cleaner, go to the wrecking yard and try to find a stock air cleaner off a Lo3 and grab the sensor off of it and install it
in your open element base. That's what I did. Even if you don't figure out a way to mount it in the filter base, you can plug it in and useing tape or a harness tie secure it somewhere and at least it will stop the comp. from throwing an SES light.

 

I thought it looked kinda funny but I checked my receipt and it says air cleaner sensor, also my Chiltons has a diagram for vacuum routing and it shows 4 hoses from the TB. Last one on the right goes from TB to air temp sensor then from temp sensor to termac door. I managed to get my camera to work long enough to snap a couple of pics.
445.jpg shows the plug of mystery
446.jpg shows what I just put on the car
447.jpg shows the vacuum diagram from Chiltons.






I drove the car again and it idles lower now (around 600 as opposed to 950) I havent cleared the codes yet, but the SES light did come on after 5 minutes which would tell me 23 is still being thrown.

 

Picture #1 is the connector for the intake air temp sensor or sometimes referred to as the air charge temp sensor by Advance auto. Picture #2 is indeed the vacuum switch that controls the flapper door in the snorkel. Get the correct IAT (or ACT) sensor and install it into the air cleaner and then clear the ECM. That should clear the code 23. Code 32 is the EGR and is another story altogether.

 

Ok, so i just wasted $23 for that other part. Not a huge deal I guess. Should I put the cap back on the vacuum source at the TB for that door flapper or leave it connected like that? I like mentioned, the car is idleing lower now with that vac line hooked to that thing. Also I wonder if code 23 is causing code 32 at all? I know 32 is EGR related, but one definition I read of 32 was Fuel mixture too rich with EGR open. Wouldnt the car be "choking" itself because of code 23 (temp measured at -22 degrees for longer than 5 minutes) I thought, maybe since it thinks its super cold out, its running really rich and thats causing the code 32 to trip as well.

 

You can plug it off at either the TB or at the output fitting of the vacuum switch, you'll get the same result: better idle. It's possible for the 23 to be a factor with the 32 but more often than not it's either a bad egr valve or vacuum solenoid. Could possibly be just a bad vacuum line to the solenoid or the valve. TBI is also known for having code 32s that just can't be solved sometimes no matter what you try.

 

The MAP, ATS, and OXY sensors all effect fuel ratio. One bad sensor or poor vacuum signal will effect EGR operation because of cyl. temps. from rich or lean conditions. I would block off the vacuum to the snorkel flapper (being you don't have one anymore) because I think it only effects open loop operation. The valve in the sensor would open sending full vacuum to the snorkel flapper to open all the way after warm up. Have you checed vacuum readings at idle yet? Not having your ATS pluged in is effecting fuel ratio somewhat that part of the fuel ratio equation is missing. I'm guessing that when you clear the codes, your 32 will go away along with the 23. Be sure to check the vacuum lines to the MAP and EGR. If you haven't replaced the OXY sensor since you've had the car might want to concider that. I've heard that Bosch is not a good choice for replacement though because of some overlap of signals to the ECM compared to AC/Delco. I didn't know Lo3's came in IROC's. I thought they came with something better that that! At least TPI w/220hp or better.

 

I dont have any guages to check vacuum with unfortunatly. I know the previous owner replaced a few sensors before I took delivery of the car, I just cant remember which. The car runs great with the exception of some hesitation just off idle when trying to launch hard. It wasnt hesitating during the colder months, but now its starting. I am 99% certain that this from the missing ATS.
And yes IROC's did come with LO3's. It was the base motor, of course it was also the top end motor for an RS.