2002 bonneville idle miss and p0171(SOLVED)

[dkc]

Ok im stumped .please excuse my bad grammer.2002 se 3.8 175000 miles ran great until 2/26/2014 never a CEL no problems.
on the 26th went for gas was driving around town no problem sitting at idle in parking lot car stumbled started to miss and voltage
gage droped just tap the gas and voltage gage right back to normal at the same time my break pedal feels much harder then normal.So i drive home runs fine down the road no power loss voltage gage fine until i stop at a light or idle it will miss
and random voltgage gage drop no CEL yet.I thought my fuel pump was pulling to much current and not providing enough
pressure ,so i pulled the 20 amp fuse and used a 10 amp fuse it would not blow the fuse i then put my dmm in the circut
instead of the fuse set on 20 amps dc pump only pulled 4.3 amps at idle 4.7 when reving no current spike when the voltage
gage would drop.So then i checked pump pressure KOEO 49-50 PSI running WOT 59 PSI no drop in pressure on throttle snap.
i figured the pump was ok .I did not find any vacume leaks yet ,swaped 2 different maf sensors no change , maf unpluged
idle rpm shoots to 1400 and runs ok normal idle was 500-600 rpm steady.Its late and about 7 deg in the garage i quit.
The next day the 27th i go to autozone to have the alt. checked it passed .Now as i drive away from autozone my CEL comes
on go back to autozone scan for codes and get DTC PO171 lean bank 1,and still have miss at idle.I have checked all my wires
for spark at the coils with an inductive timming light they all fire.So now i am at a loss.

[crash93ssei]

When was the last time the plugs were changed?

I would try some MAF cleaner, just spray it on the MAF wires, if needed very gently rub them with a q-tip.

[dkc]

I changed the plugs mid summer 2013 .I have tried several different maf sensors .I will try cleaning the orig maf.

[dkc]

Ok friday night my large plastic coolent elbow let go about 25 miles from home i replaced them in the parking lot with the aluminium ones just to get home .When i got back home i pulled the maf sensor cleaned it let it dry over night that did
not solve anything.Soon as the car reaches operating temp. 198-200 deg. the alt starts randomly droping below middle
of the gage the miss and code p0171 are still there.I still cannot find any vacume leaks.

[RJolly87]

What are the chances you got bad gas?

[dkc]

I thought about bad gas the gas i put in right before this all started should be gone by now .I have added gas at least 3 more times
since from different stations.
Thanks for the reply.

[Archon]

Have you checked the corrugated tube from the EGR to the LIM for a vacuum leak?

[dkc]

Ok i found a bad vacume leak between the master cyl and break booster . there is a rubber seal in betwwen them is that a vacume seal that can be replaced? or is the booster toast?.

[Archon]

Rock Auto has the part available as part of the replacement check valve.

[dkc]

The part that rock auto shows looks like the check valve gromet,not the seal between the booster and master cyl.

[Archon]

Gotcha. I misunderstood where the problem was. It sounds as if your booster is bad. You may want to send a PM to Andrew (Harofreak00) to see what he has.

[dkc]

Ok this has fixed all the issues in my orginal post .The rubber seal between the master cyl and break
vacume booster was torn causing a bad vacume leak i did not have to change the booster just
the rubber seal .I tried to post a picture but cannot.Thanks for all who replied,and i hope my solution
my help someone else.

[Archon]

Thanks for reporting back.