| From | Message |
J and J Auto
GenII
 
6/18/2008
03:25:13
|
 Subject: The A/F system check
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Message:
I hear this to much about people doing mods
losing power and mileage when even changing
just the plugs and wires
Even some new computers just do not do there job
As Hughes Engines put it a person would be better
off just getting a computer that works rught than
doing any mods
The Air/Fuel ratio is the key to it all power
performance and gas mileage
About 1 out of every 8000 trucks out there has
a computer that does not work
The A/F system must work properly
Heres how I check that and you can set it up the
same way or find a shop that has a A/F ratio
reader
I have in my truck and extra o2 bungs to check
this on problem trucks
A Nordask anolg A/F meter a Nordask quick reacting
o2 sensor
Now as I have on my truck a extra bung a seporate
o2 sensor and the anolog meter which will read
from 12 to 18 A/F
crusing light load 14.5 to 15
excelleration 13.5 12.5
coasting down hill upto 16.5 17
Here is your power
Here is your gas mileage
Now to check the system ether set this up or
find a shop that has a A/F reader
get a tee and a short piece of hose and a simple
LP gas torch hook it into the PCV line run the
truck now turn the torch on and feed the motor
some LP and watch the ratio change and the
computer should readjust the ratio in a mater
of just a few seconds if it does not you have
a system that is not operating correctly
This is the 1 in 8000 trucks with the problem
I try mods no change or runs worse better plugs
and wires worse gas mileage less power
As I said in the exhaust temp post 99.9% of the
shops dealers and garages have no clue how to
check this fix it or even aware that this problem
even exsist
It takes a very savy tech that is almost imposible
to find who is even aware of this or even how to
begain to solve the problem
It starts with the o2 sensor or sensors
a small signal loss from o2 to computer
worst of all just a computer that just
does not work as it was designed to
This is how to find the problem with the system
now figure out why it does not work correctly
now fix the problem
Heres 2 guys same truck same options 1 guy gets
22mpg the other 15mpg why well after reading this
post you should know why
Just something so simple I like the way Hughes
Engines put it the guy would be farther ahead
just to have a computer that worked right than
doing any mods
now if we switched computers on these trucks I
would bet any amount of money that exactly the
oposite would be true the guy getting 15 would
now get 22 the guy getting 22 would now get 15
This holding true only after making sure the o2's
are working properly and there is no signal loss
to the computer in both trucks
Heres a big problem mopar has so many splices
in the harnas just between the comp and the
o2 that a signal lose in not unusual at all
The Air/Fuel ratio is the key and the system
must work correctly and readjust in a second or
2 or you will never win the fight here
The computers A/F ratio adjustment system must,
MUST work right or you will go nowhere very fast
This test is so simple and so cheap to do and will
show the problem within just a few seconds its
just to good to be true for you guys with the
bad mileage, low power just a dog and even a
worse situation created by chrysler themselfs
getting on of these bad systems not working
properly making the truck ping than just pulling
timing out to solve the problem making the truck
even less powerful and fuel efficieant is a joke
This instead of solving the real problem of
Air/Fuel Ratio system just bogals my mind
I may have gotten a little long winded here but I
am trying to have you all understand what is
really going on here with these computers and
the most important thing they must do and
do RIGHT
Just think about what the old time racers would
have to go thru making a run pulling the plugs
changing the jets making another run
Now we have test equipment that can read this
ratio in 2 seconds and computers if working
right can readjust this is just a few seconds
Technology is great it can also be a nemisis
just hiding below the surface
feeding that motor some LP gas and watching the
ratio change and readjust in a few seconds is
fantastic do it at idle run the motor at 1000rpm
test there than at 2000rpm than at 3000rpm
watch it change and instantly readjust itself and
heres a litle clue if it takes more than 3 to 4
seconds its not working right the computer checks
the air fuel ratio like 60 times a second and
should readjust within 2 secs or its bad
This is where all these poor guys out there with
doggie trucks getting crap mileage I just feel
so sorrie for I wish I could just be everywhere
and help them all out
I don't have a customer with a V6 that gets less
than 20mpg not a one when they drive normal with
just a little hot rodding 20 or better the V8's
are also 20 or better on the highway and some of
these trucks came to me after being to the dealer
getting 14 15 mpg or less
I took the time and got them right and I have
many very happy people on the road I have some
2 wheel V6 Daks getting 26 27mpg this is the
older guys who never hot rod or break the speed
limit
These people are so happy at least twice a week
someone brings me a pizza knowing it is my
favorite thing to eat
This world really needs some changes people
should help one another not try to scew everyone
around them just for more money especialy the
big businesses all they want is your money and
screw you
Larry
J&J Auto
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J and J Auto
GenII
6/23/2008
00:33:48
| RE: The A/F system check
IP: Logged
Message:
Humm
I find this odd not even 1 comment on this
And being the most important thing the computer
has to do
Larry
J&J Auto
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01DakSport
Dodge Dakota
JOIN HERE
6/23/2008
11:01:05
| RE: The A/F system check
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Message:
i gotta tell ya thats probably one of the most informative things ive seen on this site. i always hear ppl talking about how their dakotas get crappy mpg. especially a v6 making 14-15?! thats about where i fall and thats if i drive like a gramma and shift 1 3 5. sounds like a perfect weekend project to me.right after my durango TB and cold air intake.=)
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dakota49
Dodge Dakota
JOIN HERE
6/23/2008
20:54:46
| RE: The A/F system check
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Message:
Larry, I can see where you are coming from and it does make sinse to me. Mine is an 88 and I am getting better than most of the newer trucks. When I rebuilt my engine, I had the block decked, and the heads milled, that raised the compression fromaround 120# to 180#, plus I can adjust my timing I think that helps a little as well. I also have the Halo's, and NGK 02. I am very happy with my "old truck".
I'm getting 18-22 around town, and 22-24 on highway, though I'm not a real fast driver, highway 65-70 we have a 70 MPH speed limit where I live.
Thanks for the long post, I think most of us can appreciate it.
Good Luck
Dakota49
1988 3.9 4X4 5speed
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jjk656
Dodge Dakota
JOIN HERE
6/23/2008
21:40:23
| RE: The A/F system check
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Message:
what if i dont have lp gas.. is there another way to test this?
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LOL
Dodge Dakota
JOIN HERE
6/23/2008
23:01:39
| RE: The A/F system check
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Message:
"and it does make sinse to me"
SINSE ??????????
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screwuphead
Dodge Dakota
JOIN HERE
6/24/2008
01:26:53
| RE: The A/F system check
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Message:
excellent post here Larry!
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pete
Dodge Dakota
JOIN HERE
6/24/2008
10:37:04
| RE: The A/F system check
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Message:
This test Larry is long forgotten procedure I know I was taught in my training days when carbs were about with a exhaust gas analyzer very essential to the experienced mechanic that I have used in diagnostics to pinpoint problems.The problem like many dont have access to LP gas so aside you could opt for carb/throttle body cleaner to and watch it on a scan tool as well as volt meter. Hats off to you Larry for a great post that many could utilize alot POOR MILEAGE blunders.I would of thought everyone thinks Iam to complex to post this thought and not understand where I am coming from but there you beat the punch and clear and stern to what is really going on with these trucks. Go enjoy your pizza before I get to it!! leave me a slice......
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J and J Auto
GenII
6/25/2008
23:13:54
| RE: The A/F system check
IP: Logged
Message:
You can buy an LP gas torch at any hardware store
Yes another way
Manualy lift the egr but thid only posible on the
obd1 trucks 96 and up have no egr but you could
pull a vac line and lean out the mixture and see
if the computer compensates
You can just take a vac line from the egr valve on intake and as easy as just sucking on the
vac line will lift the valve
I know its a mess but a very true thing that is
going on and most will never find or check the system operation
Larry
J&J Auto
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pete
Dodge Dakota
JOIN HERE
6/26/2008
09:35:54
| RE: The A/F system check
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Message:
Yea, that sums as you say to ripping off the consumer and lot of mechanics lost and blame on something else and disturb example timing and telling the average consumer this is your problem and not known to us savy mechanics know better in most timing is not adjustable on late model trucks,cars etc. I know we can play around and alter the crank sensor but many dont even know how to do that more less a parts replacing technician,why should I get my hands dirty like Ive posted in earlier posts and this is we come in fix the problem if you take the time not go through a lousy test procedure and get to a point in the testing and stop at saying "sensor bad replace" come on at how much an hour for troubleshooting and diagnostics people need to wake up most want it fixed now and fast so I can get back on the road leaving a boomerang waiting to return and most of all unhappy customer and confused mechanic.Probaly babbled on several different subjects here hopefully I didnt confuse anyone.... Larry anymore pizza left?...
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J and J Auto
GenII
6/27/2008
03:28:52
| RE: The A/F system check
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Message:
I like chrslers fix
The death flash
They know its running lean and pinging so instead
of fixing the real problem easy lets just
pull some timing and let it go out like a dog
Now the guy has a gutless wonder that sucks gas
like a pig
Makes the customer real happy think he will ever
buy another dodge
How discusting is that
Larry
J&J Auto
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ftheabus
Dodge Dakota
JOIN HERE
6/27/2008
09:19:38
| RE: The A/F system check
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Message:
Once the 'death flash' is applied can the 'puter be reflashed back to its original configuration? Don't see why not and then attack the problem as you suggested.
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Dan M
Dodge Dakota
JOIN HERE
6/27/2008
10:56:04
| RE: The A/F system check
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Message:
Can't you get a decent check of the a/f ratio from an obdii scanner and the short term fuel trim at idle for a baseline and then with throttle applied?
- Dan M
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pete
Dodge Dakota
JOIN HERE
6/27/2008
18:41:19
| RE: The A/F system check
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Larry definetly the death flash is a lazy way fix like a bandaid on sore wound. Dan thoughts maybe run up a spreadsheet sounds insane but might be helpful I guess Iam one of those number crunching junkies that like to look at all the variables and whats going on with a paticular system...
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J and J Auto
GenII
6/28/2008
00:05:56
| RE: The A/F system check
IP: Logged
Message:
You can watch injector response but it will not tell you if the a/f is were its supose to be
You can get the computer reflashed by an after-
market shop who flashes but chrysler will not
change it back
Heres another one that chrysler does injector sync
they will not set it past 0 when they know dam
well they run better at +3 to +6
Like some poor guys who have converter failure
over and over again this is caused by the a/f
ratio being way off and chrysler does nothing to
solve the real issue
I really like this one chrysler does
tells the customer that is normal such things as
rough idle, flat spots among other things
All it takes is just one little glitch in the comp
and it appears to be working properly but in
reality the a/f ratio is not right
One real easy way to judge this is by plug color
they should be a light to med tan color and the
same on every cyl if white or black its off
most guys with power and gas mileage complaints
there plugs are white and chrysler than tells
them this is normal they run lean thats bull
We tested this and ran plugs 2 ranges colder and
they were still white if the motor is not running
eficiantly the power and gas mileage will take
a big hit.
It just makes you wonder about them sometimes
and there factory trained techs
But first you need to be dam sure all the sensors
are working properly if so and still lean its
the computer
o2
TPS
engine temp
IAT air temp
map
this all togather control a/f ratio lets say the
engine temp is reading cold it will run rich
reading hot will run lean
but even with this condition the plug color will
either lighten up or darken slightly
but even these being off a little the o2 and
comp should compensate to adjust the ratio
its a catch 22 deal
Larry
J&J Auto
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pete
Dodge Dakota
JOIN HERE
6/28/2008
08:06:58
| RE: The A/F system check
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Message:
Another vaild point with plugs my #1 check this is your window frame if you know how to correctly read a plug.I used have a customer come on in for a oil change, plugs changed air/fuel filter change and tell me got keeping running lean to keep the carbon out of there every 3000 miles try explain this one considering the car was newer with no problems on bill when myself knew it was running lean and always tweak his carb idle mix screws bit on the richer side and every time he came for the 3000 maintenance I would find this changed and asked and always told nobody touches this car but you guys hmmm... but being a stubborn senior citizen set in his ways I just made him happy by telling him yep your running lean and clean see you next time, if I only save all those plugs Ive changed for him, then he probaly thinking I am ripping him off if I showed him every time he came in plugs just as they came out of the box then he remark saying that hes on fixed income only spend this much.My boss was always pushing for sells not truth unless it was his family member better take the time here and for everyone else WTF I say to myself but this is what lead his bussiness to Chapter 11 and me in the streets with an unpaid SnapOn tool bill my coworker and me knew it was coming but he didn't listen to us thats were my sour note of being good mechanic and no one can take that away from me, still use simple principles as you post and was taught it goes a long ways even with todays technology improving but guys like us know better what to do to fix the problem. And best one is in a bottle all those additives for your fuel another bunch of crap there, enough my babble... little to much coffee and got up to early
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Dan M
Dodge Dakota
JOIN HERE
6/28/2008
09:20:13
| RE: The A/F system check
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If you know the PCM is working properly and you're at 14.7:1 a/f then short term fuel trim should be at 0%, neither rich nor lean - in theory anyway.
If the STFT is +% then means PCM thinks vehicle is running lean and is adding fuel. If STFT is -% then PCM thinks vehicle is running rich and is subtracting fuel.
This is a good way to test the sensors you mentioned above Larry. These sensors are what causes the PCM to adjust the fuel mixture, the STFT is the result of the PCM fuel adjustments.
If the STFT is always near 0% (due to normal O2 operation of switching between rich/lean you will see a little variation of the 0% both +% and -%). If you see large change 1 way and not the other or if the STFT % is fairly high (both +% and -%) then you know the PCM is having to add/subtract a fairly large amount of fuel then you need to do further troubleshooting.
Here's a thought for you Larry. I changed the 02 sensors in my dakota about 20k miles ago with the NGK you recommended. The sensors I pulled out were denso (I purchased truck used at 45k miles from dodge dealer). The denso sensors were switching a little slow. I figured why not just change. The new NGK sensors switched faster, I thought I had done a good thing. Then I bought my 08 avenger R/T. I hooked up my autoxray 6000 to it and watched the o2 sensors .. man those buggers FLY! they change 2x-3x faster than the new NGK's in my dakota.
- Dan M
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ryan
Dodge Dakota
JOIN HERE
6/28/2008
14:01:54
| RE: The A/F system check
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I've been reading this and it's all very informative. My truck's been knocking and I think it's been running rich. Let me know what you guys think I should do because i'm pretty much at a loss.
(I posted this on another forum but no one answered me)
first of all, it seems that on a cold start the knock is really bad and slows down when the engine warms up, but it''s still there. also, the engine backfires sometimes when cold and it sounds (and feels) like it''s backfiring in the y-pipe.
it cant be a bad plenum gasket because when i swapped to a hughes stage one manifold I put on the plenum re-enforcement kit (guaranteed to never blow the gasket again). also, there does seem to be alot of black sooty residue that builds up inside my tailpipe. The last time I changed my plugs, they were pretty black. All of this normally would point to a bad o2 sensor but that would result in poor mileage. my truck usually gets about 20 mpg city/highway mixed, so it does not seem to be affecting milage. I do have a 180 thermostat, but that wouldnt matter because when the truck is started for the first time in a while it''s going to be cold no matter what, and thats when the knock is at it''s worst.
I have a stock computer and a stock ignition except for a good cap and rotor and some low resistance wires. to me, all of this info points to not enough timing causing there to be unburned fuel, but as we all know you cant just adjust the timing. The only other thing i can think of is that an o2 is getting lazy and not doing it''s job on startup but once it gets warmed up starts working ok. I would like to be able to confirm this before changing o2''s. I am going to be changing my plugs again in the next couple days. does anyone think opening up the gap a little might help? im open to any suggestions.
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Dan M
Dodge Dakota
JOIN HERE
6/28/2008
19:09:39
| RE: The A/F system check
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Message:
hey ryan. I would not look to o2 sensor first because at start-up (cold engine) the o2 sensors are NOT used in open loop. When the engine warms up and goes to closed loop that is when the o2 sensors used.
In my old 95 with 3.9L I had a backfiring problem and it was a pain to find. Finally after a week or two as I was driving I noticed my temp guage bounce! I knew my temp sender was good. Swapped the temp sensor.. backfiring went away!
I suggest you buy or borrow a scanner. I bought one of the cheaper ones for $100 and it was pretty limited. I finally recently spent a little cash and bought an autoxray 6000 from a place on the internet. I found a really good deal for it. I got it and the chrysler enhanced cable for around $320 shipped! it does obdi and obdii.
it will show you the o2 sensor as well as coolant temp and a host of other stuff (autoxray.com)
back to your problem, sounds like you are running too rich from what you described.
during warm up pcm takes into account
battery voltage
crankshaft position sensor
engine coolant temp
intake air temp
map sensor
tps sensor
camshaft position
park/neutral switch
a/c select switch
warm-up is before the engine reaches normal operating temp.
also check your battery! I just replaced plugs and battery (replaced the battery becase the neg terminal was coming out of the battery!!) and my reving idle problem when cold seems to be solved!!!
good luck
- Dan M
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J and J Auto
GenII
6/29/2008
02:50:06
| RE: The A/F system check
IP: Logged
Message:
Get some good plugs like the NGK Vpower at $2.40ea
FR4 stock range
FR5 1 colder
and be sure your air filter is clean
Check both your
engine temp sensor
IAT incoming air temp sensor
Also the map sensor if its telling the comp that
the engine is under more load than it is will
pull timing and run rich
If either is reading cold it will run on the
rich side the computer thinks the engine or
incoming air is cold
take a look at the o2 sensor)s from cold start
4.8 4.6 min if lower either sensor or resistance
in wire under 4.6 it will never operate corectly
sensor supply is 5 volt but none of the sensors
should read higher than 4.8 all sensors same
that run on this computer supplyed 5 volts
I have also seen computers with a supply voltage
being low than nothing works as it should effects
all sensors
3.8 1 min
2.8 2min
will begain its flip flop 2 to 2 1/2 min if not
its lazy even 2 1/2 is getting lazy most should
begain fliping whithin 2 min un less its like
30 below 0
this is the max time it should take
the lower flop .1 to .3
upper flop .9 to 1 volt
.3 to .8 bad this is pushing the window of
operation .4 bad .7 bad
As you can see there are many things that can
effect the a/f ratio you need to eliminate all
of these things first if all ok than take a
look at the computer not doing its job
It takes a good mech to check things out and
most don't the scanner says nothing wrong so
to them there is nothing wrong this is a bad
thing and than give the customer a bunch of
bull that its normal and the way its was designed
to run this really pisses me off when I hear
this get the vehicle to work on and find many
little things wrong that were never even
considered or checked
A scanner cant tell you everything
Yes on some of the newer vehicle the sensors
begain to operate at lower temps and move very
fast especialy on the high performance engines
they need to react very quick
I have a few customers like that myself that say
they never touch anything but are always tinkering
around mostly older guys
I got a guy on the carb screws once I used some
white out that you use for typing errors and made
a dot on the screw and 1 on the carb and it was
moved LOL he just laughed and said I guess you
caught me
I have also seen many businesses go under from
saying they did things or changed things but
never did, I have a supply of zip lock bags in
the shop and always put there old parts in them
and set them in there vehicles, I know of 1 shop
that would only change 1 or 2 plugs and charge
them for all of them this guy is long gone now
Like the one guy said I am in business to make
money not friends, I told him a happy customer
is one that will come back he said I was steeling
his customers and only stayed in business for
just over a year in a small town stuff like that
gets around real fast and no one will go there
Larry
J&J Auto
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J and J Auto
GenII
6/29/2008
03:41:18
| RE: The A/F system check
IP: Logged
Message:
I will add this little tidbit
and as someone else has mentioned here and I have
said in many posts
YOUR SPARK PLUGS truly are your window to see
exactly how your motor is running
If you do not have a book that shows you plug
examples and colors just put reading spark plugs
into any of the search engines and you will find
pics online you can look at
Must be a light to med tan sandy color also on
the reg conventional plugs if you look at the
ground strap you will notice a color change along
its length the change line should be right on
or just above or below but very close to where
the bend radious is on the ground strap
Reading this is also a great way to determin the
optimal gap if its a little low open the gap this
will increase spark intensity and raise the change
line if high to close to the end of strap close
the gap this will decrease spark intensity
jumping a bigger gap increases intensity a smaller
gap will decrease intensity
This will tweak each induvidual system for
optimal operation
no 2 systems are the same
Now I am getting into super tuning your system
And all plugs should be very close in color to
each other if 5 of 6 are fine and 1 black or
white that cyl is not right and should be looked
at to see why
bad wire, cap plug itself. Bad injector or a vac
leak will cause this
having just 1 cyl not running upto snuff on the
V6 will effect power performance and gas mileage
when all cyls are producing the same amount of
power you run smoth and run well
I guess I do get rather long winded and carried
away at times but its just my nature to try to
help everyone, I have always been that way
I don't crisize people for asking dumb questions
or doing dumb things when they do I try to
explane what happend or what is going on so they
will know and understand, that is how people
learn and find out things
Not everyone was rebuilding carbs and tunning
motors when they were 12 years old like I was
doing in my fathers garage and end up owning
the business
I look at it this way everyone has the opertunity
to learn diff things in there life and they need
to be respected for the things they know not
critisized for the things they don't know
That is why I take the time to explame things I
know and use what I know to help others
It takes all kinds to make up a world
hers another way to look at the respect thing
I would not want a dentest working on my car
nor would that dentest want me drilling on his
teeth
Larry
J&J Auto
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