Help! Fighting code 25 lean bank 1

[Tjpinkston]

92 Ls drivetrain swap into f100 pickup. Used complete harness and instrument cluster from donor car. Running driving great aside from a dtc code 25. Comes on as soon as motor warms up after a ecu reset(I assume as soon as goes into closed loop) Occasionally get both 25 and 26 and sometimes 25 comes on at initial start. Egr block off plates and a 10k ohm resistor on egr temp sensor. Have a Cai built with a cone k&n. 2.5" duals with no cats and 40 series mufflers. Secondary o2 sig wires spliced into primary's at ecu. New denso primary's. Coolant temp and afm both ohm good per factory spec. New plugs, wires, caps, and rotors. Timing marks align. Bank one checks @~350*f at heat shields on all 4 cylinders and bank 2 is @~130*f. So there is def a lean/rich cond going on. All injectors pulsing good, checked with stethoscope, fuel filter is new, and jumping fp to +b makes no difference. I have a spare ecu, same problems. Tps is functional (ohmed) and set per Toyota. Running out of ideas and need some help.

 

[George_R]

Try swapping primaries, will the lean condition swap between banks as well? Leaking intake gasket or air leak into exhaust may also contribute to the situation. Don't forget to check harness for damages

 

[gloverman]

Have you checked the mixture between the two sides with a gas analyser or widebands? I don't like splicing the signals together. Everytime I find vehicles wired like that they are having issues so I wire the engine correctly and everytime it has fixed the issues.

 

[Tjpinkston]

Have not checked mixtures. Had same dtc with original o2 sensors. Bank 1 was white colored indicating lean when replaced. No change with new sensors. Secondary's are only used to detect cat function and were wired to primary's to eliminate a fault code. I have not desoldered and tried.

 

[gloverman]

How long did the engine sit around for? We service a lot of injectors and frequently see large variations in the flow rates. Also checking for air leaks might be a good idea. dont forget the EGR ports can sometimes have internal leaks where they are blocked off

 

[Tjpinkston]

Sat approx 3 months. Pulled from running driving donor. Ran several tanks with sea foam added. Local guy seems to think that egr delete is the culprit. I'm thinking it would be affecting both banks not just one. Have checked for air leaks but can do again.

 

[George_R]

Since egr stuff is located on the driver's side of intake manifold, and that's bank1 side, I would say some correlation is possible.

Have you tried an ecu which isn't supposed to run egr? i.e. a jdm one?

 

[Tjpinkston]

Both are 89661-50032. Us models. I'm planning on doing some testing this morning and will report back in a couple hours

 

[Tjpinkston]

Checked for intake leak again. No increase in idle using carb cleaner on all lines and gaskets. Tapped on fuel rails at each injector with wooden dowel and small hammer. Desoldered the secondary o2 from primary and left unhooked. Went for 25 mile drive with mixed city / hwy driving and a couple stops. No cel...yet. Running fine no pinging hesitation or backfire. If anything it's a little better. Checked temps on manifolds upon returning home. Same problem temp wise. Driver side 330-340*F pass 125-135*F. Did not get a chance to swap o2s. Next on the list to try before reinstalling egr.

 

[1uzma70]

this may be a silly thing for me to ask but how many miles are on the engine? has it ever had a rebuild of any other modification? and have you check the ohms in the injectors? or have you changed the injectors at all ?

 

[George_R]

In addition to swapping primaries, don't forget to run one more test: leave o2s in place but rather swap connectors (by lengthening engine harness), that trick pretty much clarifies what's going on if the problem is related to o2 sensors

 

[Tjpinkston]

170k on donor car. Stock injectors. All are pulsing via stethoscope. Leakage could be possible. But not picking up any excessive fuel odor or smoke from exhaust. Doing Xmas traveling today but should get more testing done tomorrow evening and will report back with results.

 

[samsdad]

I chased a similar problem on an LS400 a couple of years back. Tried everything until we went "old school" and tried another pair of ignition coils on it. That fixed it but what was happening was when the engine got upto operating temp the coil located above the A/C compressor would break down under load and thus fire a weak spark, the ECU in turn would think that the engine was running too rich and pull the fueling back which would then leave us with a "Lean bank 1" condition. This vehicle had done 220km from new and was all original, new plugs and leads were fitted as part of the "Diagnostic" process

 

[George_R]

one more thing, gross leakage could potentially lead to the same error code, but usually it's easily detected. You just stop the engine, wait a tad, open throttle and see if it smells like fresh fuel from intake manifold.

I personally never seen leaking on 1uz, but many 1jz's has fuel trims well under -15% on slight loads, due to leakage.

 

[Tjpinkston]

Ok have a little more info from today. Ohmed both coils and primary's and secondary's checked good on both. Picked up a new coil for testing purposes and installed on bank 1. Same issue. Swapped bank 2 with old coil from bank one. Same issue. I think it's safe to say the ign is functioning correctly.

I then moved onto the o2 sensors. Removed both new primaries and Ohmed both heaters. Both were 6.4 ohms. Old take off was 6.3. Swapped bank one and two with same result. I did notice that When engine is warming up voltage fluctuates between vf1 and vf2 from approx 1.4v and effictively 0 v(this is with meter lead on vf1 and vf2 just to check difference in v. ) I would think both banks should run the same with minimal difference. Vf1 to e1 is where the ~1.3v fluxuation is occurring from 2.2 to 3.5, vf2 holds steady in 2.2-3 range) Once engine and sensors are at operating temp vf1 seems to function like it should and vf2 stays at 4.98v. No change with throttle position or rpm. Vf 1 fluctuates as it should when revving engine. Same exact result with my spare ecu. What strikes me as odd is you can switch engine off and restart and vf2 will read 2.2-3 ish range at idle for a minute or so then jump back to 4.98-99.

I listened more carefully and all bank 2 injectors are pulsing similarly.

Voltages checked a the diag connector in the engine bay.

 

[George_R]

You probably misinterpreted vf1/2 pins as being similar action as vf pin on older toyotas
here're some details
http://alflash.com.ua/vf1.htm

Perfectly, vf1 and vf2 must both be around 2.5v and NOT vary much over the whole engine's rev/load range

 

[Tjpinkston]

Thanks George. That article does give more insight into the voltages seen. I did jumper te1 and e1 and both vf1 and vf2 are switching at 8hz or more(per tsm). I cannot see exactly what the values are because my dvom is slow. I may pick up a cheap analog meter to help with this. So with the values I am seeing with te1 open the ecu is detecting a "lean" condition on bank 2 and doing a 11-20% enrichment. Based on the low exhaust manifold temps I am seeing on bank two I think the lean condition may be false. I guess my next step is to ohm out o2 wiring on the bank 2 primary sensor. I do not think there could be a fuel injector issue since it appears that enrichment is occurring as ecu is compensating. I still have not tried to reinstall the egr but may try just to see. Thanks again for all of the advise and I will update when I have more info.

 

[Tjpinkston]

Did a little more troubleshooting today. Installed an old primary o2 on bank 2 and cut the signal wires. I installed a jumper between oxy1 and oxy2 in the diag connector. This should make the fuel trims identical for both banks. Reset ecu to clear mil. No mil after a 25 mi test drive and it is running fine. Manifold temps were surprisingly the same as before bank 1 350-375*f checked at the heat shield and bank 2 was 165-180*f. I was hoping to see the temps more inline with each other. Since this should have leaned out bank 2...???.....,. Can someone with an IR temp gun shoot their exhaust manifold heat shields on both banks so I can have a reference. Thanks

 

[Tjpinkston]

Update: compression checked and inspected spark plugs tonight.
1-202psi
2-204
3-200
4-203
5-185
6-206
7-210
8-204

Checked with engine warm, fuel pump unplugged, all plugs removed, and throttle closed. Numbers seemed a little high to me so I checked my tester against the gauges on air compressor. Was dead on.

Reinstalled new bank 2 o2 sensor and removed jumper between oxy1&2. Still runs great but bank 2 is 125-160*f lower than bank 1 on exhaust manifold.


Spark plugs still looked great on both sides. Insulators were a very light shade of brown. No rich indication. Cyl 6 showed a little oil on plug but compression looked fine. Cleaned an reinstalled. Also double checked all gaps at 1.1 mm;good. Wires also ohmed good.

Triple checked cam timing; good. Confirmed #1 was indeed at TDC with dowel rod.

I'm waiting on a ebay egr vsv and am plannin on reinstalling it, unless anyone has an other ideas. I seem to be fresh out.

Will be data logging with scan tool when local shop gets obd1 adaptor in also.

 

[George_R]

you can instead build your one obd1 adaptor for dirt cheap, but obd1 stream don't have too much useful things. In fact, the difference between banks is best monitored from fuel trim point of view, and you already have this data from your vf1/vf2 checking.