2001 Grand Prix GT 3.8 Rough Idle - Page 3 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 06-14-2015, 10:46 AM   #21
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Thanks for replies: Yes the above show vacuum in state I found it when it was rough idling and with yellow pencil I stuck in it which stopped rough idling.

Yes OEM plugs I took 3 rear broken off plugs inside head out with an easyout tool. Phew! and replaced with originals with new OEM.

1st/Front 02 sensor replaced with Bosch NON-OEM, mistake?

Cleaned MAF sensor but not replaced

Fuel Filter likely never changed since it is rusty as hell. I am planning on replacing it ASAP.

BRAND new dual exhaust put in from CAT back No leaks all good there. Manifolds appear to be in decent shape but dunno about gaskets.

Just have to find out where the vacuum line goes yet even though within helpful guys told me it goes to HVAC controller? EVAP? then canister in a long run to front of engine?

LOL My $900 good deal is turning into a $3K nightmare but maybe when all is said and done we can drive it on 3 speeds since OD is shot for hopefully 2-3 years... Shagrin
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Last edited by hoarybat; 06-14-2015 at 10:49 AM.
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Old 06-14-2015, 11:51 AM   #22
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Is there a vac diagram/emissions sticker in the engine compartment(usually on the radiator support)? Like others have said, if your air flow is correct under all modes in the HVAC, then don't worry about it...just keep it plugged....

That'* a bummer on overdrive......but there should be a code set for that in the PCM....does it shift from 1st to 2nd ok? If it does, then it'* not the shift solenoids...
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Old 06-14-2015, 06:48 PM   #23
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I got these pics off my 2001 LeSabre 3.8 (non-supercharged) - The single large hose coming off the vac source goes to the Brake Booster. Here'* the illustration for that:


Here'* two pics, one from the driver'* side and one from the pass side. It appears as if that top connection has a cap on it, so plugging yours with a crayon should be ok - unless your vehicle used to have something drawing off that port.. I haven't been able to find out about that yet.

I just notoced there is a bolt missing from a retainer. Anyone know what size thread and length that one is? I guess maybe someone HAS been back there working on something before - the plenum or rear VC or both. I can see why the rear VC would leak, the stabilizer brace is bolted to it..



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2001 Grand Prix GT 3.8 Rough Idle-2rxyanr.jpg   2001 Grand Prix GT 3.8 Rough Idle-2e506zp.jpg   2001 Grand Prix GT 3.8 Rough Idle-10f4ch2.jpg  

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Old 06-14-2015, 11:06 PM   #24
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Thanks John01, Mike the Admin posted this earlier in this thread of mine: "Usually only 2 hoses come off that fitting on the backside. One goes to your brake booster(large hose) and the other goes to your HVAC controller. Unless you have electronic climate control that does not use vacuum, then stick a bolt in it and be done with it. But I'm going to assume that there is a vacuum hose laying back there somewhere."

from Wikipedia for 2001 pontiac GT: manual dual-zone climate-control replaced the optional electronic automatic unit previously offered

Maybe I am supposed to have a cap too but what mike says above implies I shouldn't and a complete hose instead of cap should run from here to the HVAC controller wherever that is. I also read within here that my evap canister is somewhere under the car near the gas tank. Maybe I should start there and go backwards toward the engine.

Here is the car from outside it sure looks good despite all the issues I have had to repair:
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2001 Grand Prix GT 3.8 Rough Idle-0614151745a.jpg   2001 Grand Prix GT 3.8 Rough Idle-0614151746.jpg   2001 Grand Prix GT 3.8 Rough Idle-0614151747.jpg  

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Old 06-15-2015, 09:15 AM   #25
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Quote:
Originally Posted by Tech II View Post
Is there a vac diagram/emissions sticker in the engine compartment(usually on the radiator support)? Like others have said, if your air flow is correct under all modes in the HVAC, then don't worry about it...just keep it plugged....

That'* a bummer on overdrive......but there should be a code set for that in the PCM....does it shift from 1st to 2nd ok? If it does, then it'* not the shift solenoids...
Yes it shifts fine from 1st to 3rd. WHen I am in D-Drive on highway going 60 and drop it to 3 there is no RPM increase showing the downshift so I am assuming 4-Overdrive is Shot. I also found a lot of metal dust fragments in bottom of tranny pan and on magnet when I changed tranny fluid and filter. Thanks
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Old 06-15-2015, 09:21 AM   #26
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Quote:
Originally Posted by Tech II View Post
Is there a vac diagram/emissions sticker in the engine compartment(usually on the radiator support)? Like others have said, if your air flow is correct under all modes in the HVAC, then don't worry about it...just keep it plugged....

That'* a bummer on overdrive......but there should be a code set for that in the PCM....does it shift from 1st to 2nd ok? If it does, then it'* not the shift solenoids...

Nope no diagram. Car shifts fine from 1st to 3rd. WHen I am in D-Drive on highway going 60 and drop it to 3 there is no RPM increase showing the downshift so I am assuming 4-Overdrive is Shot. When I am on level highway ground going 60 RPMS are at 2700 which implies Overdrive is gone? I also found a lot of metal dust fragments in bottom of tranny pan and on magnet when I changed tranny fluid and filter. Thanks
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Old 06-18-2015, 04:04 PM   #27
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Default UPDATE it aint the fuel filter OBD2 issues

Well for $7 I replaced the original fuel filter. No luck with that clearing the code P0171 running lean. Didn't think so anyway but ruling things out. Got an OBD2 cheapie ELM327 but it would not connect with the ECU via my smartphone on this car or my 2003 Caravan. It worked fine on my newer vehicles using Torque Pro. Maybe the MAF replacement is next haven't found the vacuum line yet. Can anyone recommend a OBD2 bluetooth adapter that is compatible with this car or a thread which has details.. Thanks

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Old 03-29-2016, 07:14 AM   #28
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Originally Posted by hoarybat View Post
Well for $7 I replaced the original fuel filter. No luck with that clearing the code P0171 running lean. Didn't think so anyway but ruling things out. Got an OBD2 cheapie ELM327 but it would not connect with the ECU via my smartphone on this car or my 2003 Caravan. It worked fine on my newer vehicles using Torque Pro. Maybe the MAF replacement is next haven't found the vacuum line yet. Can anyone recommend a OBD2 bluetooth adapter that is compatible with this car or a thread which has details.. Thanks
I came across this post while searching for EGR related issues. A P0171 is an obvious vacuum leak. That crayon tick you're doing is not going to solve it. You need to spray carb cleaner while its running to find ALL of your leaks. The P0171 may be the reason it does NOT go into overdrive. As far as the cheapie ELM327 device I bought one from Amazon and it works great. Try it with OBD Car Doctor Free
at the Google Play Store.
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