1996 LS400 P300,P0302,P0308 Running rich on bank 2 only
 

Hi fellas I am working on 1996 LS400 that is giving me a dificult time to repair, done basic tune up cap, rotor, spark plugs, air filter,cleaned mass air flow, checked for vacum leaks, checked for spark,compression test,etc.. ,..anything i cold think of the will help we find the problem but no luck,... here the story, when engine is cold it run smooth no problems ildes perfect no issues,engine strong, very responsive, as the engine warms up it starts idle rough and misfire i get P0300,P0302, P0308 no other codes and its running max rich on bank 2 same side cylinder misfires, any help will be great thanks in advance..

Been here done this...

Unfortunately I had to go through it before this thread was made: https://www.clublexus.com/forums/ls-...capacitor.html

When the car gets hot, unplug the green coolant temp sensor under the plug wires and see how it runs.

My money is that this car need an ECM rebuild. The way it is running should show leakage of one of the 6 capacitors if you remove the ECM and spread it open.

A question for you, do you work at a shop and this is a customers car?

thank for the quick reply Banshee365 i been floating that in my head like wtf else could it be my last guess was the ECM but i wanted to do some research first and correct myself maybe what iam doing wrong, i will try that next open up ECM hope to find some results

The other thing that will make one side run a different air fuel ratio and time dependent is the O2 sensor.

Usually what causes those symptoms involves the coolant temp circuit. The capacitors fail and the reference voltage spikes up beyond 5V. This makes the ECM think the car never warms up so it keeps pouring tons of fuel in.

Yeah but not just one side. And 96 OBD2 and full CAN implementation, things not the same as old gen 1 stuff.

Yea, only one side being affected is a little odd. But I would still check the ECM capacitors for leaking because the number of weirdo issues a bad ECM can cause is nearly endless.

Honestly I am not totally educated on how ECM's handle fuel trims with regards to how they look at the oxygen sensors and other sensors. I would be surprised if the bank 1 o2 sensor only handles bank 1 fuel trims and so on. But maybe it does. The o2 sensors would be easy to diagnose as you can just swap upstream o2 sensors since they're so easy to R&R.

All easy stuff with just a real time scan tool, and that's the good thing about OBD2.

I'd simply check the ignition system of the bank2. Can you observe the arcing that travels more than 10mm at the end of each spark plug cables on the bank2?

I'm not sure about the LS but I have alot of nissan ECM tuning experience and the two banks are totally separate with respect to closed loop trims (short term, long term, ect). The only thing in common is the base fuel and timing maps which are fixed.