Fuel bank readings

  
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Fuel bank readings

 
Evilangel Evilangel
I watched Corvette Summer | Posts: 5 | Joined: 04/12
Posted: 11/08/12
06:04 PM

When monitoring my fuel trims my long term fuel bank 1 always reads 3 more than long term fuel bank 2. Is this normal, and if not what are the possible cause of these reading?  

waynep71222 waynep71222
Duntov Incarnate | Posts: 241 | Joined: 04/12
Posted: 11/08/12
06:58 PM

vacuum leaks ...

clogged fuel injectors..

exhaust leaks..

slight differences in how the valve seats are sealing..  or slightly more wear on one valve guide..
could also be a leaking valve seal..


oxygen sensors that were not replaced in pairs..   or one thats slightly contaminated...

so many things..   3 points in fuel trim is really not a LOT

since fuel trims IS an OBD2 term...    does your scan tool have a function for graphing the oxygen sensor waveforms...    if it does... bring the engine rpms to around 2500 and HOLD your FOOT ROCK steady.. don't worry about tiny fluctuations in RPM.. you don't want the throttle valve or TPS moving... so you can look at the system in feedback mode...

there are several articles online about oxygen sensor waveform..

bosch has a good section on it from their australia site..

top pdf file down load on the right side of this page

http://www.bosch.com.au/content/language1/html/4566.htm

you will want to read from page 2.. through 22...

if your scan tool does not Graph the oxygen sensors.. see if you can pick up one of the HF98614 scan tools.. they do graph sensor voltages really well for an inexpensive scan tool..

you can swap the upstream oxygen sensors from side to side.. and see if the fuel trim numbers switch.. that would indicate the oxygen sensors might have one thats tired..  if the numbers do not follow.. you might have another small problem.  

Evilangel Evilangel
I watched Corvette Summer | Posts: 5 | Joined: 04/12
Posted: 11/08/12
07:39 PM

Great info Thank you.

Something you said caught my eye, "contamination" so what would cause contamination? Would that be something that would resolve on it's own?  

pepsi1 pepsi1
Duntov Incarnate | Posts: 88 | Joined: 01/12
Posted: 11/08/12
08:16 PM

Do you ever use a fuel addative?
  I use a Techron every oil change and never have a problem. If it's an injector this will help. It also helps the intake valves. It will never get rid of all the build up on an intake valve. The longer the deposits build up the harder they get on the intake valve.

Bob  

waynep71222 waynep71222
Duntov Incarnate | Posts: 241 | Joined: 04/12
Posted: 11/10/12
09:25 AM

"contamination" of the oxygen sensors is usually from antifreeze that gets burned through the motors from internal coolant leaks...   leaking intake gaskets... leaking throttle body gaskets on some models... leaking head gaskets...      antifreeze left in the intake ports or combustion chambers after repairs...  i have always wondered about when it overheats and puts out a spray of steaming coolant and that gets pulled into the air cleaner inlet..


another contamination comes from SILICONE...     there are Oxygen sensor safe silicones out there.. yes.. they are more expensive..

the silcones can emit vapors while curing and when heated that get into the crank case... the PCV system pulls them into the intake manifold where they are burned..   since silicone is a product of BEACH SAND as far as i know.. it coats the surfaces of the oxygen sensor insulating the components and preventing the tiny amount of electrons from flowing between the parts.  this slows down the reaction time and the signal strength of the oxygen sensor output..

were you able to copy and paste the bosch link i posted above.. ??  

Evilangel Evilangel
I watched Corvette Summer | Posts: 5 | Joined: 04/12
Posted: 11/12/12
04:45 PM

Yes I was able to get the Bosch info. Thanks this is all been very helpful and informitive.