I searched the forum and found tons of info but none of it has helped so far...

Im getting a nasty sputter at idle and hesitation on acceleration but once the rpms are up it runs great... stinks like hell and im getting 100km less a tank

I started by replacing the 2 upstream o2 sensors because the heater was gone in one

fuel pressure is good and way back i did the intake gasket and spider upgrade, and fuel pump

found a vac leak on the hvac hose, replaced hose but found atf in the old one (diff zoo of problems)
I plugged off both hvac and 4x4 hoses at the check t-valve to eliminate any vac leak sources in the diaphragm actuators..

I replaced plugs and wires, cap, and rotor all with dialectic gresse

yesterday i pulled the dizzy to find a nasty looking gear so replaced the dizzy with a good one

changed coil and module


with the engine warm and at idle

LTFT1 25%
O2 B1S1 .04v

LTFT2 -3.91%
O2 B2S1 .89v

O2 B1S2 .78V

MAF 4.8g/s

Codes are: P0171 System too lean (bank1)
P0300 Random/Multiple cylinder misfire detected



today i tried swapping o2 B1S1 for another one i have and it still reads the same.. also tried unplugging all the o2 sensors and they all read proper .44v or whatever it was that is a baseline

i checked for vac leaks and found nothing
i want to pull my hair ouT!

 

Have you checked the coil? you replaced plugs wires cap and rotor what brand did you use? chev and gm they tend to be very finicky , pricey but A/C Delco is the brand that solves most issues

 

yea i replaced the coil and module... ive got garbage new out of the box ngk plugs and wires but just acquired newish acdelco wires.... the cap and rotor and coil are all standard t series brand.... i know ive heard time after time acdelco is the only way to go.... i hope this isnt going to be a very expensive lesson.... im figuring all these new garbage parts were better than the old worn out stuff i had and the problem was long before i changed this stuff...

 

you might get away with the ngk wires but cap and rotor should be changed to ac delco might be enough to fix your problem, if price is an issue you could always check someplace like kenny's u pull find one off a newer year that would be an option

 

When an oxygen sensor reports a lean mixture, the PCM starts adding more fuel trying to satisfy the oxygen sensor. You confirmed the rich mixture by your statement: "stinks like hell and im getting 100km less a tank". B1S1 is reporting a lean fuel mixture, (.04 volts) and fuel trim, (PCM adding fuel) is extremely rich, (25%). The key here is that YOU know it's running rich, but the oxygen sensor continues to report lean. Best to go through the flow chart to diagnose it, but if there are no exhaust leaks, and if I were a betting man, I'd bet the farm on a bad B1S1 oxygen sensor There may be other issues, but we need to start with that.


At the oxygen sensor: Zero volts indicates an extremely lean mixture. Yours is reporting .04, (not much above zero). .45 volts indicates a perfect fuel mixture. .9 volts is the highest voltage an oxygen sensor can produce, and it indicates a rich mixture.


4.3L's need to have AC Delco plugs, distributor cap & rotor, and good quality wires. Denso, Delphi, or AC Delco oxygen sensors.

 

poured some water on those wires tonight and they have a very faint blue glow in some spots and little bit of arcing going on near the cap plugs..... i wonder what kinda warranty and return ngk has....... pieces of junk i say!!!!!!!!

 

Bad wires could very well be contributing to the rich mixture, (fuel not being burned) but the fact remains that the oxygen sensor is not reporting correctly.

 

well what do you know.... new acdelco cap and rotor, and 1 new acdelco o2sensor for b1s1, and the used/newish set of acdelco wires from the wrecker i got for 6$.....
it SEEEMMS to be running great.... ill report back if it goes array again..... thanks all for the great help..

 

Good job, thanks for posting back!