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 Chasing down code P0171

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Cliff96
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Name : Cliff
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Chasing down code P0171 Empty
PostSubject: Chasing down code P0171   Chasing down code P0171 EmptyMon Nov 30, 2020 2:27 pm

I've been chasing a lean code P0171. I found 1 vacuum connector leaking and fixed that which changed it to an intermittent code. My cheap scanner only shows freeze frame data. Here's the freeze frame at the time of the code: load % 7.1, ETC 93 degrees, short term fuel trim 10.9, long term fuel trim 16.4, MAP in Hg 15.1, rpm 1718, MAP (lb/min) 2.366.
Does any of this tell someone where to Look? I may just have to get live data.

Thanks in advance

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albertj
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albertj

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Chasing down code P0171 Empty
PostSubject: Re: Chasing down code P0171   Chasing down code P0171 EmptyMon Nov 30, 2020 5:50 pm

In my experience on the factory vac harness (rubber connectors, nylon air lines) the rubber connectors are all "done" at the same time.  You found one leaking?  OK.  If any of the others pull easily off their metal nipples, they are likely leaking as well.

Also, did you check your exhaust manifolds for cracks?  You will likely need at least an inspection mirror to look at the undersides - it's hard to feel for puffs of exhaust under there without getting burned  a mechanics stethoscope might work though...  I had a leak that I could not find - I wish I'd asked Mooch (one of the techs at my local GM dealer) how he found it, it was in the ex manifold right by/under the ignition module mounting plate.   He showed me a pic of it he took with his cellphone.  I was not *that* impressed though, the lower intake manifold leak escaped him (and me too, for quite some time - I fixed it when I replaced that gasket whilst chasing an oil leak, I had oil puddling on top of the manifold and read somewhere it was due to the LIM failing) Manifold swap is more time consuming than it is difficult, on the 3800.  There is a trick to getting the dipstick tube out of the way without breaking it, though.  Ask me how I found out (rolleyes  -- on second thought don't ask).

You also could have a failing lower intake manifold gasket.  Suspect this if your car has no whistle at idle but a mild whistle that begins at part (like 1/4 to 1/2) throttle. The engine, supercharged or not, does not whistle.  That's another job that is typical for the Riv at higher mileage and although it costs a little cash (under 100)  it takes a lotta time (part of that 100 is the case of beer to share with the buddy or 2 you recruit to help... jk...).
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Cliff96
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Name : Cliff
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Chasing down code P0171 Empty
PostSubject: Re: Chasing down code P0171   Chasing down code P0171 EmptyMon Nov 30, 2020 6:28 pm

Thanks for the info. Are the rubber connectors still available to buy? I think if I find a crack in the front exhaust manifold I'll replace it with a power log 😀
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Z-type
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Z-type

Name : Andrew Zamiska
Age : 34
Location : Cecil, PA - 25 miles south of Pittsburgh
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Chasing down code P0171 Empty
PostSubject: Re: Chasing down code P0171   Chasing down code P0171 EmptyMon Nov 30, 2020 8:45 pm

That info seems to point to a vacuum leak. 16.4 LTFT's are topped out dumping fuel so I'd say it's excess air.

What year is your car? There's are some 'vacuum harness' kits out there depending on which L67 or L36 you have.

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Cliff96
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Name : Cliff
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Chasing down code P0171 Empty
PostSubject: Re: Chasing down code P0171   Chasing down code P0171 EmptyMon Nov 30, 2020 9:05 pm

It's a 96
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albertj
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albertj

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Chasing down code P0171 Empty
PostSubject: Re: Chasing down code P0171   Chasing down code P0171 EmptyTue Dec 01, 2020 12:36 pm

Cliff96 wrote:
It's a 96

You can get a vac line kit "by mail" from ZZP for $20, or make up about the same for yourself (same price + or - $5) with rubber vac/fuel hose (any decent auto parts store) and two Tee fittings. I forget the smallest inner diameter needed but you can match that up at the parts store. 4 feet of that hose and a couple tees & you're good. When I needed vac hose I went to the parts store and the counterman asked to look under the hood and I pointed to the vac line. he said, "oh yeah" and sold me the hoses I needed -- turs out he and his buddies had done more than one 3800 and looking at the engine jogged his memory. I think the IDs were 1/4" and 5/32 or some such.

Word to the wise: consider replacing all the vac lines. Reason is they are all the same material and subject to the same conditions, which means all the parts are likely toward the same degree of failure. There is one vac hose that is tricky on my car, a molded U shaped hose near throttle body. I made that up using a couple appropriate diameters of rubber fuel hose, with the narrow part a bit longer so it would make the bend without kinking. I glued it together with tire cement (like for patching bicycle inner tubes). It's been years (about a decade?!?!) I think since I made that thing up. It's still fine.

Another word to the wise: it would not surprise me if you sprayed starting fluid around your intake manifold with the engine running that you would discover at least one leak, but it would make me (and you no doubt) happy if there's no such leak. The gaskets are not free but they are not that much $$ either.

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Cliff96
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Name : Cliff
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Chasing down code P0171 Empty
PostSubject: Re: Chasing down code P0171   Chasing down code P0171 EmptyTue Dec 01, 2020 4:19 pm

The nylon vacuum lines look new but the angled rubber connectors don't. I also see aluminum coolant elbows and a metal edge on the manifold gasket. The valve cover gaskets look like they've been leaking oil for awhile though.
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98inWPB
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Name : Ed
Joined : 2020-01-04
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Chasing down code P0171 Empty
PostSubject: Re: Chasing down code P0171   Chasing down code P0171 EmptyTue Dec 01, 2020 7:08 pm

albertj wrote:


Also, did you check your exhaust manifolds for cracks?  You will likely need at least an inspection mirror to look at the undersides - it's hard to feel for puffs of exhaust under there without getting burned  a mechanics stethoscope might work though...  I had a leak that I could not find - I wish I'd asked Mooch (one of the techs at my local GM dealer) how he found it, it was in the ex manifold right by/under the ignition module mounting plate.   He showed me a pic of it he took with his cellphone. .

A no special tools way to find exhaust leaks (I suppose intake leaks as well but never tried)

Shop vac output blowing into the tailpipe with a rag wrapped around for a mediocre seal (plug other side with rag) Use a squirt bottle with soap water and spray anything suspect.

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Cliff96
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Name : Cliff
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Chasing down code P0171 Empty
PostSubject: Re: Chasing down code P0171   Chasing down code P0171 EmptyTue Dec 01, 2020 7:27 pm

I'm all for no cost thumbsup
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Cliff96
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Name : Cliff
Joined : 2020-09-01
Post Count : 131
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Chasing down code P0171 Empty
PostSubject: Re: Chasing down code P0171   Chasing down code P0171 EmptyTue Dec 01, 2020 7:33 pm

When I took off the blower snorkel to replace the coupler the support leg that bolts to the manifold underneath was missing part of a cardboard like gasket that was under where the bolt goes thru. I some rtv there. Is it possible for it to leak vacuum there?
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albertj
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albertj

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Chasing down code P0171 Empty
PostSubject: Re: Chasing down code P0171   Chasing down code P0171 EmptyTue Dec 01, 2020 10:34 pm

Cliff96 wrote:
Thanks for the info. Are the rubber connectors still available to buy? I think if I find a crack in the front exhaust manifold I'll replace it with a power log 😀

Actually you don't need the rubber connectors. You need a few feet of vac hose that will fit the nipples on the engine (manifold etc) and a couple hard tees (brass or plastic) that will fit the hose. Replace the rubber tees with hard tees that have a short length (2 cm) of vac hose where they connect to the engine.

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