Today we did some more tuning and saw something interesting. We were watching both L&R O2s at WOT. The Left O2 was the typical rich at WOT remaining flat around .900 through the pull. The Right O2 was Oscillating as if it was at idle DURING WOT. Shouldn't it be flat rich?

What would cause the Right O2 to Oscillate at WOT? Is there a table that is off?

This is a '95 LT1 M6. It doesn't matter which gear we are at WOT but it was very obvious in 3rd and 5th.

 

O2s are a monitoring device. Their data comes straight from them not a table. Typically the engine goes pig rich at WOT and if I remember correctly, the PCM ignores the O2 readings also.

More than likely you are seeing an actual lean condition at WOT which begs the question "what are the conditions of your fuel system?" much less anything else as you have given us next to nothing with regards to your equipment.

Perhaps your fuel system can't keep up with the demand. What is the pressure doing during all this?

More information would be needed.

 

try swapping the o2's and see if the problem moves. If it does, you have a bad o2.

 

What was the range of the right O2 mV's when this happened?

 

Speedy - Here are my upgrades:
95 Z28 / 1LE - T56

Fuel - Delphi #38 Injectors, Walbro 255 pump, upgraded pump harness

Induction - SLP CAI, K&N dual air filters, 58mm Edelbrock TB, TB Bypass

Valvetrain - Ported & Polished Trick Flow Heads by JMS Racing Engines, Manley Undercut Valves, Comp Cams Custom Grind, 1.6 RRs Pro Magnum, Manley Pushrods, Forged Stroker Crank, 5.85" H-Beam Rods, Beehive Valve Springs

Cam Specs - Lift 0.528 In / 0.576 Ex, Duration 270 In / 280 Ex, LSA 112.

Exhaust - Edelbrock Ceramic Coated TES Headers, Off Road Pipe, Ex. Insert Cone, Edelbrock Cat Back Exhaust

Ignition - Jacob's Ultra Pack Ignition, Coil, Trigger, MSD 8.5mm Plug Wires, NGK TR55 Iridium Plugs

Drivetrain - Hurst Short Throw Shifter, SLP Alum Driveshaft, LG Torque Arm, GM 4.10s with Eaton Posi, SLP Lightened Flywheel and Centerforce Dual-Friction Clutch Package

* The left bank O2 shows the typical 0.900 steady rich reading. The right bank O2 oscillates as if the car was idling or at cruise. It is as if the right bank Injectors are idling or at cruise (instead of WOT) which shows the oscillating right O2 reading. I'm open to suggestions

Onefast - I can swap the O2s, but they are both reading so I'm not sure if the problem would follow the O2. If the right O2 is oscillating and responsive, then it is active. So, I'm thinking it is something with the right bank of injectors not going to WOT though I'm not sure how that is possible as I'm new to programming.

Injuneer - the left O2 was steady 0.900 during WOT. The right O2 oscillates between 0.175 and 0.900 in a typical cyclical pattern.

 

If the fueling was truly like idle the car would fall on its face WOT.

 

Are your fuel trims the same under moderate load or do they split? Most likely items in my experience is an exhaust leak or vacuum leak, or if the fuel trims are not split all the time, a misfire on the side with the goofy o2 trace. Being most obvious in the higher gears, probably a plug/wire or something of that sort. I have seen cars guys swore up and down had no misfire and sounded good at wot, but were lacking power and did just exactly as you are describing. Could be something like cracked porcelain or damaged/nicked/burned plug wire etc. The problem is often times not obvious and we're talking about all new parts in many of these cases. So thats where i would look.

I could mention some other things but I don't think its worth while at this moment to clutter things up with too many ideas and stick to the simple things first.

 

Onefast - yes, the car wasn't running right and would fall flat on WOT. Almost like a misfire, so we hooked it up to the DataMaster and watched the O2s and discovered that one was operating as it should and the right O2 was still oscillating.

WS6 - The BLMs are pretty even all the way through with the exception at idle. The Left BLM is hanging at 115 and the Right BLM is at 128. Odd since the right O2 is the one that is oscillating. Regarding the misfire, that is possible and I will check mid-week... never know. But, to me, it would seem that if one was misfiring that the right O2 would still be somewhat of a flatline (or reasonably close to one) at WOT and not oscillate.

 

What you are describing is one bank staying in closed loop and one bank going to open loop at the same time. I don't see how that is possible. Can you post the tune and the Datamaster log file?

 

If it misfires that blows a cylinder full of unprocessed air straight across the o2 which is dead lean due to no combustion. Then you get the others blowing a rich air fuel mixture across it. Consider the latency of a regular narrow band o2 sensor and thats what you get, oscillations from one extreme to the other.

I have only seen one time when a bin file that had been modified with lt1 edit where one of the short term blm's was still active under wot despite the blm locker being active. This also caused a symptom like you're describing, it is a really out there chance for this to be it. To explain how rare I have seen this one time in hundreds of cars and thousands of tunes/logs. I have seen a couple dozen times where weak spark was it, and numerous other times when it was other mechanical issues.

It would be helpful to see the logs you are talking about if you can host the file somewhere I will take a look at it with the big eyes for irregularities. Or you can always email it to me if you would like.

 

You know that at WOT the engine should be rich.
You know one bank indicates it is running rich at WOT.
You know it appears that the other bank is not rich.
You know it falls on it's face.

Look for a problem of fuel delivery on the side that "appears" to not be going rich. Like gunk build up inside the fuel rail on the side in question.

 

I will ask my programmer for the file. I don't know if he recorded the phenomena but we both saw it on the DataMaster. Next tune will be on the 20th... The 13th is the Internationals. I will be under the car Tuesday night and will check for misfires.

 

The right rail supplies fuel to the right bank, then the excess fuel crosses over to the left bank. Gunk in the right rail, where he is seeing erratic O2 readings, would affect both banks.

 

Update - I checked the car for arcing sparks. Turned the lights out and didn't see any stray sparks. I pulled the wires and inspected them. They all look good.

Currently, my tuner is at the Winternationals so I will be unable to get the file until next week. We will be on the Dyno for the final tune on the 20th.

I checked the PCM ground and it is directly on the block and is tight. Looks clean.

I'm still wondering why the Left Bank raises normally when the throttle is snapped and why the right bank oscillates like the car is idling. Do you think it may be something in the Injector Harness?

He is running Tunercat but not the latest update. Could that be why the right bank of injectors are not getting the signal to enrich? When I snap the throttle I get a lean backfire through the intake.

 

Could it possibly be the ECM? Would a battery disconnect reset the ECM?