Unexpected reaction after gutting air box (back in the hunt) - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 03-13-2007, 11:12 PM   #1
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Default Unexpected reaction after gutting air box (back in the hunt)

After i gutted the back box in the SSEI, the car isn't running the same. At stop and idle, the boost gage reads up a couple of points and there'* a slight vibration in the steering wheel. Before it would read -10 and the wheel was dead still. It seems like the engine is asking for more air, like it'* choking a bit. This not what has happened before. Usually the car almost immediately gets smoother.

I had the battery disconnected, reconnected it and have driven about 30 miles. Also when I sit it at idle the coolant temperature goes up. It never did that before either. It stayed pegged at 195+/- no matter how i long i let it set idling.

The only thing i could think of is that missed some loose plastic in the box and it'* on the MAF screen now.

What could be up?
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Old 03-13-2007, 11:28 PM   #2
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Inspect your MAF screen, then put it all back and give it some time to re-learn how to idle.
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Old 03-13-2007, 11:34 PM   #3
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Quote:
Originally Posted by willwren
Inspect your MAF screen, then put it all back and give it some time to re-learn how to idle.
Remove the TB per techinfo?
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Old 03-13-2007, 11:36 PM   #4
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While it'* out..also check all the vacuum lines in the area under the airbox and at the throttle body. Ensure the IAT is plugged in.
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Old 03-13-2007, 11:42 PM   #5
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Quote:
Originally Posted by BillBoost37
While it'* out..also check all the vacuum lines in the area under the airbox and at the throttle body. Ensure the IAT is plugged in.
I scanned al of the sensors and they are all reading. New symptom, in park or neutral, the engine'* smooth. As soon as I engage a gear the boost gagee starts fluctuatiing slightly and the idle has a wider variance.

edit: i know, I'll swap in a spare back box i have. if it goes back to normal, then the MAF isn't clogged.
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Old 03-14-2007, 12:30 AM   #6
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Normal amount of air, it barely does it. I just swapped in the stock box, without disconnecting the battery. It could be re-relearning. How long does it take for relearning idle?

It'* easily has 2 or 3 times the air available with the gutted box. the throttle just loves it. I took it out on some familiar hills and there was definitely some more power.

I still can't figure why more air during idle, would make the car behave like it'* choking for air.It is idling at the right speed, but the SC has to work to do it.
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Old 03-14-2007, 08:01 AM   #7
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The maf screen is in correct?
Maf is clean?

Your symptoms seem vacuum related, the boost gauge is a vacuum/positive pressure gauge. No need to hook up the scanner, visual inspection of the vacuum lines is needed.
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Old 03-14-2007, 08:55 AM   #8
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Yeah. I figured it'* working harder to pull the air in. I changed the plugs and wires yesterday and I'm waiting for the O2sensor and PCV. The TB and MAF were going to be next antway. I'll drive it 'till the parts get here tomorrow or the next day. See if it settles any. I just have a feeling I missed something when I scrubbed out the box and it whiffed onto the MAF.

Thanks for the help..
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Old 03-14-2007, 12:19 PM   #9
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Charlie.. would you please check the vacuum lines?
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Old 03-14-2007, 07:23 PM   #10
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Quote:
Originally Posted by BillBoost37
Charlie.. would you please check the vacuum lines?
Yes. Sorry i thought I had mentioned that. I checked them when i swapped in the test box. I was hoping for a line loose or split. It was dark when i did it. Things are a little different than the L36 in general, so I wanted to go over them again with the FSM this afternoon. Bill, you suggest it, I do it. They don't look that healthy, but OK. i may still suds them.

Just a BTW... I know that this might sound neo-stupid..... The front bank O2 sensor is really "slow". It'* definitely not Delco, which I always use. The one on my '95 is like lightning. The one on the SSEI seems like it has to think for a second, then shift.

This a good problem-solve for me to go through.
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