fst100

iTrader: (5)

When I got the car it had both codes on. Ltfts in the +25. Replaced both and still got the codes after resetting the ecm and the ltfts still at +25. Also noticed it would go into open loop mode sometimes at idle and cruising.

Bit history, the car was originally came as a v6 but swapped in an ls1 motor by the original owner and I'm the 4th owner now. What else could it be? Bad wires somewhere or something else?

Tia

fst100

iTrader: (5)

Also the narrowband o2 readings were mainly double digits and no higher than like 500mV

2xLS1

iTrader: (25)

Check the fuel pressure.

fst100

iTrader: (5)

whats the fuel pressure suppose to be at idle?

edit-been doing a few searches still....could a dirty MAF also be at fault? i can clean that as well just for ***** 'n giggles

2xLS1

iTrader: (25)

58 PSI. Yes a dirty maf can cause it. Air (vavuum) leak downstream of MAF too. Check them all.

fst100

iTrader: (5)

thanks 2xLS1. whats typically the stock IAC(idle air counts) counts on a near stock LS1? i recall IAC counts helps if theres a vac leak or not?

mantycarguy

Normal IAC counts should be between 10-30. If they are 0 look for a vacumn leak that would affect both banks such as brake booster hose or a faulty pcv system.Check fuel trims at idle and under various loads(fuel cells) and check freeze frame data to see where the problem occurs.

thedudeZ

iTrader: (14)

Last time I had this issue I had two things at the same time. I had missing intake gaskets(at the intake port of the head) as well as in the fuel tank the hose was busted coming off the pump and seeping out fuel pressure.

I would start with fuel pressure gauge at the rail and possibly poping the intake off and making sure the gaskets are all good. Make sure you read the writeups and don't mess up your oil pressure sending unit wire and follow the torque sequence for the intake going back on.

fst100

iTrader: (5)

just got a fuel pressure gauge but its been cold and havent the time lately. will be checking teh fuel pressure today as im leaving work early. yesterday i cleaned the MAF and the LTFTs still read +25 and the STFT +16.4 but the NBo2 has hit above 500mV a few times but if i blip the throttle in park the NBo2 reads only double digits for a bit then goes back in teh triple digits and above 500mV.

also my IAC is ~28counts so that means there's no vac leaks correct? was thinking about teh pcv if that goes bad but would it cause both pre-cat O2 to go lean?

So heres a recap:
replaced both front O2 sensors, cleaned MAF, checked IAC counts but fuel trims still showing only positive trims, never negative.

will check fuel pressure at idle.

fst100

iTrader: (5)

so the fuel pressure gauge i have is too small to screw on the schrader valve. i swapped my maf sensor with a known working one and the fuel trims are still showing constant positive values. so i went ahead and richened the MAF table via hp tuner by ~20% from 2000-3000hrtz range and it seems to be working. im awaiting a widband in the mail so that'll definitely help in tuning idle/cruise/wot. what's a good commanded AFR to shoot for on a N/A mainly bolt-on mods ls1? 12.8afr on stock 28* timing?

mannyman84

iTrader: (2)

Was the PCM and harness swapped too?

fst100

iTrader: (5)

yes i fairly certain. the pcm read it as a 98 v8 according to hp tuners

fst100

iTrader: (5)

fwiw, i think the O2 sensors that were on there before were Bosch and i swapped those out with new bosch sensors but the longer/extended ones part #13111 so i can use them when i get headers. should i get one ac delco and install it on one side of the manidold and see if thats whats causing the dtc issue?

mannyman84

iTrader: (2)

There is your problem there. Get some AC delcos

mannyman84

iTrader: (2)

Get some OE's and get o2 extensions. I've had a lot of problems with bosch o2's

fst100

iTrader: (5)

i bought one denso(had good experiences with denso on my wbody) from advance auto and will be installing it on the passenger side to see if the 0151 comes up on that side when i go full throttle. if only the driver side(still has the bosch) lights up and not the passenger then i know its the bosch sensor.

edit-this test should work like that if the sensor is faulty correct?

mannyman84

iTrader: (2)

YeAh should work. I say you have someone with a scanner check how the o2 Is working and also check the monitors to see if they have passed. denso is a good brand aswell. Nothing better then keeping it oe with the ACDELCO.

2xLS1

iTrader: (25)

Everyone needs to stop replying with suggestions until he checks and knows what his fuel pressure is. He was told to check that 2 weeks ago. You will set those codes if the sensors go to a low mv at wot. Low fuel pressure will cause that.

Or just keep throwing money at parts you don't need.

mannyman84

iTrader: (2)

Didn't even notice the codes. For lean you wouldn't have 2 o2's go out at the same time. Check for intake leak, fuel pressure, or bad mass air flow.

fst100

iTrader: (5)

i checked the rubber intake bellows yesterday and didnt find any cracks. i swapped the maf and still no go. i just got my hands on a fuel pressure gauge, but i dont think it'll help much as this only happens at full throttle/100%. doesnt do it if i am less than 100%.