Hey y'all,

I have a 1972 C10 short bed with a L92 and TR6060 swapped in it. The L92 has long tubes, BTR stage 3 LS3 cam, LS7 MAF and a Holley Hiram 103 (yeah yeah I know not the best choice for power but damn she looks killer). When I was an auto (6L80) i had random lean codes every month or two, but only after long drives. I would clear them and they wouldn't come back on so I would just forget about it. My tuner (whose the guy in my area) swore and up and down that i have more then enough fuel, which I believe because it runs great and hauls *** at the top end. Weirdly though AFTER we swapped in the TR6060 (greatest decision ever) I have been getting Constant Lean codes. Sometimes its P0171 and sometimes its P0171 and P0174. The truck runs amazing and first we thought it was the OLD Bosch O2's being grumpy so we swapped them to Denso sensors but same lights. I am not sure if its a vacuum leak because sometimes only Bank 1 gets a lean code. I have a feeling it might be the Long tube headers leaking where they meet the cylinder head since the exhaust at the collectors had to be redone to fit the Tr6060. Are there any tell tale signs? I don't have a strong smell of exhaust in the cab or under the hood anymore then I always had.

Anyone have any thoughts on what it could be? Seeing that CEL is such a buzzkill when your bullying other cars and cruising having a fun time.

Pics for Attention

 

I had a similar issue with my 414, bank to stayed lean, but injector pulse was super fat trying to bring it back but the sensor never changed its lean reading. In my case it ended up being the fuse for the 02 heater on my stand alone harness. The sensor wasnt heating up on start up, I had tried different ECM's was ready to repin and swap to the 99-02 ECM until I remembered i had a stand alone harness.

Worth a check though it sounds like you drive yours enough the exhaust would heat up the sensor on its own and resolve your issue.

 

Hmmm that sounds possible I will add that to my list of things to look over. I know when the car is cold and its running in open loop off of the tables it has an aggressive but steady idle (sounds badass) but when its warmed up and switches to closed loop (I think I have that right) the car does some idle hunting from 850-1000 rpm. Does that sound O2 related where they aren't heating up enough due to the long tubes?

 

so that's how I figured out my issue is when the ECM mine was fun until it got warm and started using the 02's to adjust the fuel trims (closed loop) then the idle would shift drop quite a bit but I have a large cam so it was hard to tell. I had to hook up a hptuners logger to see the injector pulse. once it entered closed loop it doubled on passenger bank. The tell tale for me was the delay in the rev response to pedal which was cable driven. made it feel sluggish unless I really put my foot in it.

I also had long tubes and ORY, so yeah it could be related. with a basic scan tool you can look at the O2 readings, once it goes closed loop they should switch back and forth between fat and lean trying to maintain stoichiometric AFR. should show a millivolt reading so sub.300 would be lean and above .700 would be fat. shouldn't exceed 1 volt and should always be fluctuating once in closed loop. If you have one that hangs its likely heater circuit power related. Mine wouldn't move from .320-.360 so the ECM kept giving it fuel but it wasn't responding. Those are somethings you could check on your own

and a really dumb question your rear o2's deleted?

 

I know under 2k-2.1k rpm the truck would feel sluggish but after 2k-2.1k it wakes up and accelerates much quicker at the same throttle input (i figured that had to do with the stage 3 cam and Hiram killing bottom end). we changed the O2's and the tuner took another look and made some adjustments in the tune and it woke the truck up a bit 2.1k and under. I am not sure if that was O2 related or tune related or both.

I have a basic scanner I can see if it can read O2's. What should I see for outputs on the scanner?

As far as the O2 heater theory isn't there a specific code for O2 heater issues? or that wouldn't trip with a blown fuse?

I haven't seen the tune file so I can't say 100% they are deleted, but I'm 99% sure they are since I'm not getting a bad cat code. Is that safe to assume? I would get Hptuners but I worry about messing anything in the tune up.

 

you got me thinking now because I personally didn't swap the engine in I never saw the harness. I have to tear into it to see where the fuse box would be to check on the O2 heater fuses. Is it safe to assume that it has to have O2 heater fuses?

 

on the scan tool side there should be a menu that lets you see all ECM parameters or pids, should dispaly throttle postion, rpm, coolant temp oil pressure yada yada. if you keep scolling down the list you will get to the 02 readions front and rear for both banks, you are interested in the front, as the rear is only there to verify the cats functionality and doesnt impact fuel trims. you should see a 3 digit value rangining from .1-.9 milivolts closer to zero the leaner you are and the closer 1 the richer the AFR.

Harness should have fuse block to protect injectors and 02's and a fuel pump relay

say more on this bad cat code.... this would indicate you are still using rear 02's.
p0141 would indicate a heater malfunction via short circuit or excessive resistance a fuse would generate an open circuit which I would think would qualify, but if HPtuners has disabled the codes regarding o2's (thats a question for your tuner) they wouldnt show up on a scan or trip the check engine light.

I would also be curious to know if the front and rear sensors are swapped harness wise? this could explain your issue also. So the cat should read lean as its purpose is to absorb the carbons in the exhaust gases. Downstream 02 readings should be less then upstream if system is functioning properly. If they are reversed though your ecm would A see a richer downstream reading then upstream and would try to lean the system out, and B throw a code for a bad Catalyic converter.........

this might explain why you have always had the issue as opposed to a blown fuse but id look into both.

Tuner likley wouldnt catch this because he would have been using a remote wideband 02 to tune with and ignored the OE o2's as they are useless for actual tuning for power.

 

I don’t have the bad cat code to show cat inefficiency. I’m saying because I don’t have that code popping up that would mean I have those disabled.

I have a custom LS swap harness using an E38 ecu. So it’s very doubtful that the harness has the pins swapped but it’s always a possibility.

I will definitely try to scan the ecu to get O2 readings and see what it says! I’ll check the heater circuit somehow as I only get that issue light when it’s warmed up and the idle quality changes.

my tuner is out of town til Monday so I’ll be pulling my hair out all weekend.

 

oh I dont think the harness pins are reversed I think the front o2's connector might be plugged into the rears. Even though my rear's are disabled my harness still has the connections for them. sorry I misread that you were getting a code for cat efficiency.

Hopefully its something simple for ya.

 

now that i think more on it i have been getting those lean codes way more often at night when the temperature drops... might be on to something with the O2 heater theory.

 

hopefully its that simple for you, it reslolved my issue which wouldnt have found had a not played with HPtuners a bit to see the injector pulse, from their it was the o2 data. Sometimes the swaps have quirks that arent super easy to figure out but end up being a simple fix.

 

I really appreciate the help buddy I hope it’s a simple fix so I can terrorize the streets of Orange County again 😜

I have a lead on the standard hptuner Verison 2 for $350 with 6 credits. You think it’s worth it to help me with this issue and future ones? I worry about making wrong changes. Or is the data logging one totally needed

 

If you wouldn't mind educating me a bit on the heaters for the O2's that would be awesome. Is the heater circuit baked into the ECU? or is there a heater controller somewhere I can inspect?

 

mine will be a bit different since its a 98 ecm but the functionality is likely similar. 4 pin connecter for 02's signal wires should go back to ecm, heater circuit should be controlled by the ignition relay with separate fuses for each. the heaters themselves are part of the 02 (the require an specific heat to funtion optimally) A pin out of the o2 connector would tell you which pins should send voltage to the heater circuit. they should function in open loop so running at idle you should be able to get the readings with a multimeter with the harness unplugged. If you are unsure where the fuse panel is for your harness that would be the quickest way to see if the heater circuit is behaving as it should. you should see 12v across 2 pins powering the heater circuit.

that help? what year is that l92 out of I can porbably find wiring info for that connector so you would know which ones to probe?

 

pretty sure its an early gen 4 like 07-10 I don't 100% remember. BUT i may have stumbled on the issue. I took my truck to work today and when I popped the hood to show a few coworkers I noticed that the 2 studs used for the L92/LS3 Hiram to mount the base to the cylinder heads were super loose and the nuts were a quarter inch loose and could easily be spun by hand. I never noticed it before but the light hit just right and boom I saw them unbelievably loose. I will try to tighten them down this weekend but I think my suspicion of a vacuum leak might have been correct.

After having a few old BMW (notorious for vacuum leaks) I'm prone to assume any lean code is a vacuum leak, but I ruled it out because it never had severe idle issues or surging.... the small idle hunting I assumed was from the cam. Anyone else agree I might have found my issue?

 

enough air in past the MAF would definitely contribute to a lean code hahaha

 

If it happens again, use a scanner that will show you freeze frame data so you can get an idea of what is happening when it kicks that DTC.

 

I recently got HP tuners. Is there anything I can record or use that will help show why a DTC is being thrown?

My basic scanner has a freeze frame option but always reports back as "no freeze frame available" is it because its a swap there's a BCM or something required?

 

there is a live view of data you can see wit Hptuners I believe there is just a standard view that gives the info you would want to see. Sorry been a while since I have played with it, but you would want to see Maf readings, fuel trims, injector pulse, timing and o2 readings. this should give you a good idea of whats going on. you can also record this during a driving session so you can go back and look at the data assuming you dont see anything pop.

If your vac leak on your intake still didnt resolve the issue, id be curious to see the MAF readings, MAP sensor data could also tell you what Vacuum levels are which may point out another leak if thats your culprit

 

you can set up a live data feed with some of the sensors you’re logging. Have you downloaded the scanner yet? It should have a few graphs populated and I think have some sensors in the feed