Unexpected reaction after gutting air box (back in the hunt) - Page 2 - 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 03-14-2007, 07:29 PM   #11
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Suds won't help in finding vac leaks. Use carb cleaner. At idle, you'll hear the engine rpm'* change as it pulls the fluid into the intake and combusts it.
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Old 03-14-2007, 11:53 PM   #12
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Quote:
Originally Posted by willwren
Suds won't help in finding vac leaks. Use carb cleaner. At idle, you'll hear the engine rpm'* change as it pulls the fluid into the intake and combusts it.
Excellent. Thanx.
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Old 03-15-2007, 07:15 PM   #13
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The MAF screen and TB are clean. In fact i think the TB was cleaner than the one in the SSE after I cleaned it. BUT! The rubber elbow coming out of the TB that connects to the line back to the Evap purge valve just came apart in my hands. i don't know if it was from me pulling and twisting it to check it, but I have my fingers crossed this is the culprit.

It'* a funky little piece, rigid elbow with 2 different dimension ends. I have to go to Autozone for the O2 sensor tool, can I get generic vacuum connectors there?. (Or Advance, they are 1 building away from each other) Or is this best done at the dealer?
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Old 03-16-2007, 07:20 PM   #14
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Nope. Replaced the connector and no improvement. I'm out of cards to play. It just annoys the hill out of me to see that boost gauge at -8 when I'm sitting at a light. It should be dead -10..

The handful of issues the seller had with the car I solved in about 8 hours work by using the Generally Accepted Bonneville Club Practices. It was cake. I'm sure an experienced Wrench here could figure this out in 15 minutes, if they had the car in front of 'em..

I have a leaky, whiny steering pump to tend to, then she'* in shape. Then I'm coming back to this, it has to be the vacuum or something else I did moving that airbox in and out.

D**n it

PS... pulled the Bob'* Discount O2 sensor. Had 4 tiny slots in it and was a slug. O2 readings with the Delco are lightning now.
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Old 03-16-2007, 08:53 PM   #15
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Quote:
Originally Posted by charliemax
Nope. Replaced the connector and no improvement. I'm out of cards to play. It just annoys the hill out of me to see that boost gauge at -8 when I'm sitting at a light. It should be dead -10..
Classic symptoms of a vacuum leak.

Get the carb cleaner out again. This time make sure you spray it all around the base of the supercharger and the joint on the supercharger where the main housing meets the rotor plate and nosedrive, front to back.

Inspect all your vacuum lines to the charcoal canister, shift modulator, and vac accumulator between the windshield wiper motor and maxifuse relay center. Also at the brake booster and each vacuum manifold on the supercharger itself. The PCV also.
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Old 03-16-2007, 10:24 PM   #16
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Quote:
Originally Posted by willwren
Quote:
Originally Posted by charliemax
Nope. Replaced the connector and no improvement. I'm out of cards to play. It just annoys the hill out of me to see that boost gauge at -8 when I'm sitting at a light. It should be dead -10..
Classic symptoms of a vacuum leak.

Get the carb cleaner out again. This time make sure you spray it all around the base of the supercharger and the joint on the supercharger where the main housing meets the rotor plate and nosedrive, front to back.

Inspect all your vacuum lines to the charcoal canister, shift modulator, and vac accumulator between the windshield wiper motor and maxifuse relay center. Also at the brake booster and each vacuum manifold on the supercharger itself. The PCV also.
Two new symptoms. When i introduce a load, like all-out heater/defroster, the boost goes up a bit. Also, I can hear a slight hum in the cabin. It'* steady and not throtle related. Can't hear it walking around the car. Definitely wasn't there when I got the car. I would have been on the fuel pump, because that'* the kind of hum it is.

Anyway...

I have been racing through the work on the car. Free days have been perfectly nixed by weather, and I have been doing everything racing home from work and trying to beat sunset. The 5 inches of sleet we got today will be gone in a few. I'm setting aside a day to calmly go through your punch list in an orderly military fashion. It'* important to me that i solve this myself (with the guidance I have been getting fromr Boost and you)

Much appreciated.
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Old 03-17-2007, 02:04 AM   #17
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Charlie, did you ever swap in the unmolested air box like you said you were going to do? I'm curious as to whether that would make a difference.
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Old 03-17-2007, 01:23 PM   #18
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Quote:
Originally Posted by MACDRIVE
Charlie, did you ever swap in the unmolested air box like you said you were going to do? I'm curious as to whether that would make a difference.
Yes. I did it all three ways after it "went". Stock box, modified box, and no box. The boost gauge still showed symptoms of unaccounted-for air. Whether too much or too little. It has to "boost" just to reach normal idle of 850. There is something I'm not seeing.

I'm going to carefully check around the SC and the other areas again. But my gut tells me it is a line problem from me physically moving the box in and out as I progressively gutted it, not the change to the box. The last time I put the mofified box in, I had made a very minor change to the back. And it had run great just before that.
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Old 03-17-2007, 01:27 PM   #19
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The vacuum lines to and from the charcoal canister (vapor recovery tank) are in the vicinity of the airbox. Directly underneath. But you need to go over every vacuum line with a fine-toothed comb and carb cleaner. Don't forget the lines going to the vacuum accumulator next to the maxifuse relay center. They get brittle from the heat coming up the firewall from the rear exhaust manifold.
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Old 03-17-2007, 03:58 PM   #20
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Quote:
Originally Posted by willwren
The vacuum lines to and from the charcoal canister (vapor recovery tank) are in the vicinity of the airbox. Directly underneath. But you need to go over every vacuum line with a fine-toothed comb and carb cleaner. Don't forget the lines going to the vacuum accumulator next to the maxifuse relay center. They get brittle from the heat coming up the firewall from the rear exhaust manifold.
When Boost first got to me about the vacuums, I thought those ones to the charcoal canister were prime candidates, victims of me shoving the box down to catch in that annoying center stay. I "checked" them but not really, because the PCM case kinda blocks a clear look. That'* just indicative that I need to go inch by inch on everything.

With your list, a good simple diagram of all the vac lines in the Chiltons, and my '96 FSM (haven't got a '98 FSM yet, the guy on ebay boned me) I should be able to locate everything. Anything that looks vaguely questionable, I'll replace. That one connecter to the evap purge valve just fell apart in my hand. good reason to believe there are other dried beyond proper function. I may have to come back to confirm that I got all the correct areas around the SC with the carb juice.
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