Greeting guys! Firstly i'd like to thank you guys for the past 4 years of helping me with my car without me having to ask a question. unfortunately i've come to a point where i'm entirely overwhelmed and could really use some help pinpointing let me try to be as helpful as i can

Make: Pontiac
Year: 1996
Model: Firebird
Drivetrain: 5.7L LT1 V8/4l60 A4 trans
Modifications: Pace setter long tube headers/ORY, SLP LM1 exhaust(No cats)

OBDII Codes:
P0134 P0134 02 Sensor Circuit No Activity Detected (Bank I Sensor 1)
P0141 P0141 02 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)
P0154 P0154 02 Sensor Circuit No Activity Detected (Bank 2 Sensor 1)
P0400 P0400 Exhaust Gas Recirculation Flow Malfunction
P0443 Evaporative Emission Control System Purge Control Valve Circuit
P1441 EVAP System Flow During Non-Purge Condition


Problem: Rough idle/acceleration displaying symptoms of a misfire but no misfire codes located

When is problem notice?: When car is at operating temperature, during full RPM range(I haven't yet tried wide open throttle to test for O2's) On cold starts car is completely normal

What have you already tried?(Will edit as suggestions come): Checked and cleaned EGR, Checked all vacuum lines for any leaks, checked for exhaust leaks(repaired 2), checked purge solenoid.

Recent preventative maintenance?: NGKTR55's and OEM opti approx 10k mi ago.

Comments: I never had the rear O2's hooked back up, i had long tubes installed and the car has run fine for months. this is a recent development although p1441 has always been around despite me replacing everything that has to do with the purge, no maintenance or changes occured prior to this happening, Pardon me if the answer is easy i've literally learned everything i know about working on cars from this website and other similars. i look forward to working with you guys! thanks in advance.

 

Normally, I would slam the "Opti" button on my keyboard, however, after some deeper thought...


Everything in your code list runs down the Emissions pathway. A few ideas. Burned wires or broken wires, particularly running to O2s that when cold, mechanically the circuit is close, but when the engine warms, the wire separates due to expansion? Could explain the absent activity. Also, possible bad ground? Loose ground? Its a whole ton of stuff in your code list making me think its a broader issue like a general electrical fault, hense bad ground.

 

Rear O2's will not effect performance. They only monitor and will throw SES light if exhuast gases are not within parameters. However when is the last time the front O2's were replaced? Unplug them, drive around after car gets to normal operating temperature and see what happens. O2's can start to slow down with age and can do so without triggering a SES code.

 

Alright, so when I get home I'll check all the 02 harnesses and plugs and wires. Ill keep you guys updated, i really appreciate the hasty response, I'm praying it's not the opti.. the harmonic balancer gave me so much trouble last time..

Oh another thing. What would unplugging the front o2s do? Like what would that help diagnose?

 

Unplugging the Front O2s forces your car into open loop mode. And essentially forces the car to use the MAF (correct me if im wrong) to set your air/fuel mix. It's how your car will run when you first start it cold, until it gets up to operating temperature. You are basically removing a potential variable out of the equation. If you pull the plug on the front O2s and it runs great, it pretty much isolates your issue to the sensors themselves or the harness.

 

Alright guys sorry for the late reply I work 12 hour shifts with a 1 hour commute one way lol so I'm really busy and tired most of the time, I haven't had the time to get her up on stands yet but I was able to kinda force a misfire by keeping the rpms steady high in low gear when it was warm, it started misfiring heavy, pulled code p0300( nice and useless) I parked it and on the way home today it started missing immediately even when cold, I've noticed a new symptom while I had it idling I heard what sounded like a intermittent clicking at random intervals, it sounds like what I'd imagine a sparkplug wire arcing would sound like, I was looking in the bay while it was dark and didn't see any arcs, I tried to hone in on the tick and it seemed to be most audible from the driver side wheel well. I know there's a plug or 2 down there so I'm really putting my money on wires at this point I think I'm gonna just reach around the wires until I get zapped, I didn't notice any obvious abrasions or melting to the wires from what I could see but I was in a hurry, I'll go out there and give it a solid inspection on my lunch break and let you all know if I find anything new

Also I wanted to clarify it didn't sound like lifter tick nor did was the source the valve covers

 

Hey slp I wanted to thank you for helping me take this on by the way buddy, those o2 related codes I posted were any of them related to the front o2s? Or were they all rear codes? I'm not to familiar with locations via banks

 

https://ls1tech.com/forums/lt1-lt4-modifications/1167115-cant-find-bank-2-sensor-2-my-97-z28-m6.html#post12108775

Post #3

 

not an expert but:
open loop : no o2 sensor feedback to correct towards stoich
closed loop : o2 feedback to adjust lean/rich.
Cars usually start up in open loop until temp reaches a certain point.

Re: MAF: cars use a mix of maf and speed density calibrations. The year can affect which one is most important. In fact, some may not have a MAF.
If you have a MAF and you fail it, you default to speed density.

if car runs good in open loop, and goes to hell in closed loop: o2s can be an issue, or maybe an intake leak.
Small intake leak won't show up until you switch to closed loop and you start maxing out l trims.

Btw: has the OP checked the trims ?

 

Bank 1 = side of the motor with the number 1 cylinder. In this case, drivers side. Sensor 1 is the upstream, sensor 2 is downstream and checks for cats and has nothing to do with A/F ratio.

LT1's REALLY don't like it when the 02 sensors are bad. I had one that misfired badly and pretty much wouldn't idle due to both 02 sensors being bad. Led to the worst blown head gasket that i've ever seen.

 

P0134 and P0154 are the big ones, the rest won't affect driveability. Fix those first. You said it runs and idles great when cold (open loop), which points right to the O2's being the culprit.

Try what other have suggested, unplug at least one of the front O2's (driver side is the easiest to reach) to force the PCM into open loop. If it drives good after that, there's your problem. Worry about the others later, as P0443 can be a potential PITA.

Also inspect the wiring harness where it runs around the headers. Since you installed them a few months ago, I'd bet you burned through some wires.

 

Well I've got the car in shambles at the moment, wires are definitely trashed I got some bs autozone ones while I wait for some superconductors I'll let you all know how it turns out but for now it's work time

 

Update I'm still trying to get these **** plug wires in, I got super conductors trying to go stock route. Got it just about hooked up, just have to hook up the boots on drivers side. The old wires were incredibly damaged, I will update once I get this done.


Side note anyone know where I can get a good otvc kit

 

Fixed it boys, it was the plug wires x.x I feel so dumb, I can't beleive it took me that long to put wires on this car.. atleast it should be easier next time. Thank yall for the support! Until next time cheers.

 

I know I'm late to the party but I would have also put in fresh NGK TR55s, they are $2 each and fresh plugs compliment fresh wires, old plugs are harder to spark, so sometimes that causes arcing and premature wire failure as the spark takes the easiest path to ground, and if it's arcing out of the side of a wire it can fail them faster.