1999 Bonneville SE - missing IAT? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 02-20-2010, 05:01 AM   #1
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Default 1999 Bonneville SE - missing IAT?

My car is a 1999 Bonneville SE....

I'm starting to transition slowly from a "check the fluids and change the oil" type of DIY'er to someone who, hopefully, can save a few more bucks by doing the next set of maintenance jobs myself (e.g. flush the coolant, check PCV, etc.). When getting ready to clean the throttle body this evening, however, I noticed that the air intake tube between the air box / filter and the throttle body had a dime-sized hole in it (pre-fab hole, not like someone stuck a screw-driver through it). Upon further investigation, it certainly looks like the exact position as the IAT in the photo this this thread (https://www.gmforum.com/normal-maintainence-138/intake-air-temp-iat-sensor-replace-284335/ ). My car has been getting considerably worse gas mileage recently (26-27 mpg almost 100% highway with cruise 60-70 mph vs. 30-32 mpg I got year ago), but I attributed that to new tires.

My SES light came on a year ago, and the tech at the repair place said it was a code thrown for the vapor/evaporation system. He checked out the obvious places, but couldn't find anything, and I didn't want to pay for him to continue to hunt down a small hole somewhere. As such, for the past 12-14 months, my SES has stayed on. I've had the car in for some other work in that time (most recently about 3-4 months ago as a result of misfiring that required new plugs and wires, replacing ones that had ~80k miles on them), and the techs, when they've pulled the codes, haven't said anything about an IAT sensor error being thrown. Can they IAT sensor really be missing? Again, I can stick my pinky finger into the hole in the tube (located just beyond the air box and that metal screw tightener deal). I looked around that area for any dangling wires that would tell me that the sensor fell out and got ripped apart, but I didn't find anything.

FWIW, I started to look into doing some DIY maintenance because my idle the past month or two has been rough, particularly right after starting the car. After I start the car, the engine will idle around 1500-1600 RPM until I rev it or drive away. If I drive it immediately after starting it, the car "jerk"/hesitate a bit, though that usually goes away after 20-30 seconds. At any rate, all of this got me to start looking at cleaning the throttle body, which got me to notice the issue addressed in this post. Thanks!
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Old 02-20-2010, 08:16 AM   #2
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Look around for the plug, it should be right in that area. If you find it and the IAT is there, put it in the hole. If it'* not there, just PM me. I have like 3 or 4 of them here.
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Old 02-20-2010, 10:38 AM   #3
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Yea, its possible the mechanic took the duct off during diagnostics and it might have came out without him knowing. It'* probably laying down there somewhere.
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Old 02-20-2010, 12:01 PM   #4
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Where'* does the sensor wiring terminate? I just spent like 10 minutes poking around, tracing all the wiring that I can see in that part of the engine compartment, and I just can't see any wiring that doesn't look like it belongs where it is right now.

Thanks for the quick replies!
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Old 02-20-2010, 12:55 PM   #5
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Just have to go and trace the wires again trace from your pcm to the engine( pcm is next to your air box), but until then I would really plug that whole with something. Right now you are pulling unfiltered air into your engine.
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Old 02-20-2010, 02:01 PM   #6
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Originally Posted by Nighthwk12 View Post
Just have to go and trace the wires again trace from your pcm to the engine( pcm is next to your air box), but until then I would really plug that whole with something. Right now you are pulling unfiltered air into your engine.
Fortunately, I finally found the sensor+wire dangling near the transmission. If nothing else, at least the sensor was still attached, though I'd probably have to hook up an OBDII reader to see if it'* still good anymore.

Thanks for the help!
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Old 02-20-2010, 06:33 PM   #7
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I don't see why it wouldn't be ok. Unless the wiring was jeopardized, or the sensor itself was damaged.

If it was damaged, I'm sure you would get a check engine light.
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Old 02-20-2010, 08:39 PM   #8
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The sensor should be just fine. Put it back in the hole and all should be fine.
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Old 02-20-2010, 09:41 PM   #9
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Quote:
Originally Posted by WxGuy1 View Post
My car has been getting considerably worse gas mileage recently (26-27 mpg almost 100% highway with cruise 60-70 mph vs. 30-32 mpg I got year ago), but I attributed that to new tires.
****. im thrilled if i get 20 right now. The highest I have got in the 6 months since I have owned the car is 21.8mpg. Mind you I just now diagnosed that i've had a bad MAF since if owned the car so and ill idle outside of work for like 5-10 before i go in. but I am hoping the new/used MAF I get helps that.

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Originally Posted by WxGuy1 View Post
FWIW, I started to look into doing some DIY maintenance because my idle the past month or two has been rough, particularly right after starting the car. After I start the car, the engine will idle around 1500-1600 RPM until I rev it or drive away. If I drive it immediately after starting it, the car "jerk"/hesitate a bit, though that usually goes away after 20-30 seconds. At any rate, all of this got me to start looking at cleaning the throttle body, which got me to notice the issue addressed in this post. Thanks!
I have/had the same problem. Look above. Check your MAF. Mine will idle rough for a bit, rev up to like 2500rpm come back down and idle just fine.
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