Hi,
While I have a 98 5.2L and it struggles a bit in AM when I first start
to drive then evens out in about 3 min or so, would that be MAP or air
temp sensor creating that delay. Some malfunction of something. Also,
is there a published list on line of code readouts?
This is just a minor annoyance but if something is failing I don't
want it to get any worse.
Thanks guys. It really helps to read your communiques. My son started
me on this site after I got my 98, he was running 02 Durango pretty
tricked out, used to love to ride in it but nevertheless it was sold
for a profit, so . . . .
On Tue, Sep 23, 2008 at 4:30 PM, Phillip Batson <pbatson68@yahoo.com> wrote:
>
> Wow, great info! I kind of figured it would be something like that. Thanks Bernd!
>
>
>
> ----- Original Message ----
> From: Bernd D. Ratsch <bernd@dodgetrucks.org>
> To: dakota-truck@dakota-truck.net
> Sent: Saturday, September 20, 2008 11:42:44 AM
> Subject: DML: RE: RE: Cold engine puts out more hp/tq...
>
>
> The sensor signals are put into the PCM which calculates it and compares
> them to reference values (expected values). If they're within normal range
> (throttle position, MAP, vehicle speed, for example)...the calculation runs
> as posted. On the newer vehicles (starting in 2002), the PCM can insert
> it's own values if a sensor if out of range. Example: Disconnect the Crank
> sensor on an '05 Dakota and it still starts and runs - the MIL is tripped
> but the PCM inserts its own value to get you down the road to a shop for
> repair. The ETC engines can also run without the MAP and Crank sensor
> installed.
>
> On the '07+ 3.7/4.7/5.7L engines, you can try to "tune" the PCM with a
> piggy-back system but you'll never get it right. The PCM only looks at the
> MAP sensor for initial BARO reading - once that's done...it works off of
> internal, calculated values.
>
> In the 1992 case, they're not that elaborate but expected values are still
> in place. Modifying something like the IAT can't affect mileage that much
> since there's a 33% Fuel Trim allowance. The PCM will try to get a close to
> "0" by calculating the difference in between the LTFT and STFT. This is why
> modifying an IAT sensor really doesn't do a whole lot to mileage unless you
> go way out of the normal/expected range.
>
> On the fuel adaptives...there are 26 different tables which correspond to
> MAP and Engine Speed. All of them use calculation formula.
>
> - Bernd
>
>
> -----Original Message-----
> From: Phillip Batson [mailto:pbatson68@yahoo.com]
> Sent: Saturday, September 20, 2008 11:12 AM
> To: dakota-truck@dakota-truck.net
> Subject: DML: RE: Cold engine puts out more hp/tq...
>
>
> Are any of those variables calculated or are they all readings from sensors
> on the truck?
> Another way to ask this is, does the computer just take sensor readings and
> plug them in for the calculation, or does it have something like reference
> tables in its programming to calculate certain values that may exceed
> certain limits? So, if it gets a reading for say, upstream 02, and it is
> outside some set range, does it modify what it plugs into the equation?
>
> If so, that would really limit the 'effect' any one variable has on the
> equation if there are limits setup for different (or maybe all) variables.
>
>
>
> ----- Original Message ----
> From: Bernd D. Ratsch <bernd@dodgetrucks.org>
> To: dakota-truck@dakota-truck.net
> Sent: Friday, September 19, 2008 8:58:52 AM
> Subject: DML: RE: RE: RE: RE: RE: RE: Cold engine puts out more hp/tq...
>
>
> Yup...while yes it can, it depends on quite a few other conditions - not
> just intake air temp.
>
> (RPM/Max RPM) x (MAP Baro) x (TPS x ECT x IAT x Sensed Battery Voltage x
> LTFT) x (Upstream O2) x (STFT x LTFT) = PW
>
> That's the formula. The ignition timing is also affected by IAT (but not
> just by itself) so engine and weather conditions do apply. Higher/Lower
> pressure, engine coolant temp, engine rpm, battery voltage, throttle
> position...so you're trying to tell me that they don't matter??? What about
> what the O2's read - think about those variables and how the PCM reacts too.
> Fuel mileage is dependent on a lot of variables - yes...the difference in
> between a 30 degree outside ambient and 90 degree outside ambient will
> affect mileage slightly, but again...pcm calculations need to be figured
> out.
>
> - Bernd
>
>
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