1996 LS400 P300,P0302,P0308 Running rich on bank 2 only - ClubLexus - Lexus Forum Discussion

Go Back  ClubLexus - Lexus Forum Discussion > Lexus Model Forums > LS Models > LS - 1st and 2nd Gen (1990-2000)
1996 LS400 P300,P0302,P0308 Running rich on bank 2 only >

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

Notices
LS - 1st and 2nd Gen (1990-2000) Discussion topics related to the 1990 - 2000 Lexus LS400

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

Old 09-24-16, 09:36 PM
  #1  
619miller
Driver School Candidate
Thread Starter
 
Join Date: Nov 2015
Location: California
Posts: 4
Thanks: 0
Thanked 0 Times in 0 Posts
Default 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..
619miller is offline  
Old 09-24-16, 09:41 PM
  #2  
Banshee365
Lexus Test Driver
 
Join Date: Nov 2006
Location: FL
Posts: 921
Thanked 72 Times in 60 Posts
Default

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?
Banshee365 is offline  
Old 09-24-16, 09:47 PM
  #3  
619miller
Driver School Candidate
Thread Starter
 
Join Date: Nov 2015
Location: California
Posts: 4
Thanks: 0
Thanked 0 Times in 0 Posts
Default

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
619miller is offline  
Old 09-24-16, 11:50 PM
  #4  
dicer
Lexus Champion
 
Join Date: Jul 2010
Location: ca
Posts: 4,477
Thanked 69 Times in 65 Posts
Default

The other thing that will make one side run a different air fuel ratio and time dependent is the O2 sensor.
dicer is offline  
Old 09-25-16, 12:39 AM
  #5  
Banshee365
Lexus Test Driver
 
Join Date: Nov 2006
Location: FL
Posts: 921
Thanked 72 Times in 60 Posts
Default

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.
Banshee365 is offline  
Old 09-25-16, 03:53 AM
  #6  
dicer
Lexus Champion
 
Join Date: Jul 2010
Location: ca
Posts: 4,477
Thanked 69 Times in 65 Posts
Default

Originally Posted by Banshee365 View Post
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.
dicer is offline  
Old 09-25-16, 08:42 AM
  #7  
Banshee365
Lexus Test Driver
 
Join Date: Nov 2006
Location: FL
Posts: 921
Thanked 72 Times in 60 Posts
Default

Originally Posted by dicer View Post
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.

Last edited by Banshee365; 09-27-16 at 07:09 PM.
Banshee365 is offline  
Old 09-25-16, 12:21 PM
  #8  
dicer
Lexus Champion
 
Join Date: Jul 2010
Location: ca
Posts: 4,477
Thanked 69 Times in 65 Posts
Default

All easy stuff with just a real time scan tool, and that's the good thing about OBD2.
dicer is offline  
Old 09-25-16, 06:52 PM
  #9  
Yamae
Lexus Champion
 
Join Date: Aug 2011
Location: Japan
Posts: 2,136
Thanked 142 Times in 112 Posts
Default

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?
Yamae is online now  
Old 09-27-16, 02:38 PM
  #10  
djamps
Lead Lap
 
Join Date: Sep 2015
Location: CA
Posts: 400
Thanked 9 Times in 8 Posts
Default

Originally Posted by Banshee365 View Post
Yea, only one side being affected is a little odd. But I would still check the EVM 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.
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.
djamps is offline  


Thread Tools
Search this Thread
Quick Reply: 1996 LS400 P300,P0302,P0308 Running rich on bank 2 only


Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

© 2018 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: