P0300 help!?
Senior Member
Joined: Nov 2017
Posts: 746
From: Poland
Why do You work on spark and cables while Your car is running rich:
Why don't You post pairs LT/ST as asked by George?
Why don't You post pairs LT/ST as asked by George?
Last edited by Mike.308; Mar 22, 2019 at 02:19 PM. Reason: s/lean/rich/
Moderator
Joined: Oct 2014
Posts: 4,338
From: North Central Indiana
Lots of things can cause false misfire codes. Flex plates, balancers, belt driven accessories, torque converters, transmissions, bad engine bearings, etc. But fuel trims indicate the misfire here is probably real.
Senior Member
Joined: Nov 2017
Posts: 746
From: Poland
Sry, negative trim is rich not lean. At start, You said the plenum looked flooded, right?
Anyway, You might not be getting right stoichiometric (air to fuel ratio), so it just doesn't ignite properly, and You get the misfire code.
...still these are ST trims (short term ones), that should be set in pair with LT to get a good understanding.
Number 6 intake channel is completely full of fuel. It has also has a new mpfi system installed by the previous owner.
...still these are ST trims (short term ones), that should be set in pair with LT to get a good understanding.
BF Veteran
Joined: Jan 2007
Posts: 4,628
From: Florida
Bank 2 is a mess at 2500. Your combined trims are -25 which means that the system is or thinks it needs to subtract fuel for a really rich condition. Most likely either you have some bad injectors on that bank or a bad o2 sensor on that bank.
Are the plugs fouled on that bank?
is that o2 sensor switching properly?
you can swap o2 sensors or replace the one on the wonky side. If you swap and the condition follows it’s the sensor. If it doesn’t follow it may be the injectors. If injectors are suspect you can do a balance test on the injuectors with a relatively inexpensive pulse tester and pressure gauge off amazon or just replace the injectors. The fact that it’s only one bank rules out MAF sensors etc.
george
Are the plugs fouled on that bank?
is that o2 sensor switching properly?
you can swap o2 sensors or replace the one on the wonky side. If you swap and the condition follows it’s the sensor. If it doesn’t follow it may be the injectors. If injectors are suspect you can do a balance test on the injuectors with a relatively inexpensive pulse tester and pressure gauge off amazon or just replace the injectors. The fact that it’s only one bank rules out MAF sensors etc.
george
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Senior Member
Joined: Nov 2017
Posts: 746
From: Poland
There are a great videos on YT with a fuel trims explanation, i.e. this one:
BF Veteran
Joined: Jan 2007
Posts: 4,628
From: Florida
I have never looked at fuel trims as a time graph. I look at fuel trims as tabular data, and there there may be some smoothing. You take the short term and long term fuel trims and add them together. a negative number means the system is subtracting fuel via shorter injector pulses to correct for a rich condition as determined by the O2 sensors. Totals over 10 need to be addressed. Totals over 25 set a code. I may be overreacting now that I see the time scale at the top measured in seconds. If you can get simple tabular data for all 4 numbers that would help. Also, long tern trims should not be changing that fast unless I just cant see the color codes and the fast moving lines are both short term numbers. Either way, I dont find these graphs very useful. attached is a screen shot of what you want
George
BF Veteran
Joined: Jan 2007
Posts: 4,628
From: Florida
In the example above thje fuel trims are large and positive at idle so the system is adding fuel to correct for a lean condition but the problem goes away at higher rpms. A likely cause for this is a vacuum leak which is a lower percentage of total air flow at higher loads/rpms.
George
George