High Idle 4500 RPM

In article >,
Matt Whiting > wrote:

> maxpower wrote:
>
> > Your right it isnt that nessassary. more of a reference point of open and
> > closed throtlle, u can unhook the tps sensor and the engine will run, it
> > will give a hesitation on take off but will run because the MAP sensor
> > determines load and how much fuel to deliver
>
> I don't think Chrysler publishes its ECM algorithms, but I've be very
> surprised if the TPS is used only to sense closed and WOT.

~Excluding transmission/transaxle functions~
Rate of change in order to increase the injector pulse width when
the throttle is opened.
Idle air control valve diagnostics (fault sensing)
The TPS is the least important of all the input sensors, its
biggest effect on fuel delivery is when the PCM is receiving a
changing voltage from it indicating throttle movement.

> If that were the case, they would use two cheap switches rather than a relatively
> expensive rheostat sensor.

Some manufactures have been known to do this.

> I'd also be very surprised if they don't
> make a check for closed throttle when the MAP is indicating low pressure

Closed throttle low MAP pressure is a heavy decel, which is a
whole different situation from the potential mass vacuum leak
being discussed.
A vacuum leak that can/does add hundreds of RPM to idle speed
-raises- manifold absolute pressure, raising manifold pressure is
usually responded to by the PCM by as an increased injector pulse
width.

> and thus calling for more fuel and not rev the engine wildly with a
> closed throttle. Maybe the Chrysler engineers aren't that smart, but
> I'm betting they are.

Some things are beyond the limits of control of the system.

> Have you ever seen a Chrysler engine have a vacuum leak that made it run
> 4,500 RPM with the throttle closed?

You've got a minivan or two at your disposal...
Hook up your scanner, pull the PCV or brake booster hose off,
start the engine and report back with the results, i.e., RPM
changes, MAP changes, pulse width changes.
You may not see 4500 RPM exactly, but you will experience the
causes and effect.

yup

"Matt Whiting" > wrote in message
...
> maxpower wrote:
>
> > Your right it isnt that nessassary. more of a reference point of open
and
> > closed throtlle, u can unhook the tps sensor and the engine will run, it
> > will give a hesitation on take off but will run because the MAP sensor
> > determines load and how much fuel to deliver
>
> I don't think Chrysler publishes its ECM algorithms, but I've be very
> surprised if the TPS is used only to sense closed and WOT. If that were
> the case, they would use two cheap switches rather than a relatively
> expensive rheostat sensor. I'd also be very surprised if they don't
> make a check for closed throttle when the MAP is indicating low pressure
> and thus calling for more fuel and not rev the engine wildly with a
> closed throttle. Maybe the Chrysler engineers aren't that smart, but
> I'm betting they are.
>
> Have you ever seen a Chrysler engine have a vacuum leak that made it run
> 4,500 RPM with the throttle closed?
>
>
> Matt
>

yup

"Matt Whiting" > wrote in message
...
> maxpower wrote:
>
> > Your right it isnt that nessassary. more of a reference point of open
and
> > closed throtlle, u can unhook the tps sensor and the engine will run, it
> > will give a hesitation on take off but will run because the MAP sensor
> > determines load and how much fuel to deliver
>
> I don't think Chrysler publishes its ECM algorithms, but I've be very
> surprised if the TPS is used only to sense closed and WOT. If that were
> the case, they would use two cheap switches rather than a relatively
> expensive rheostat sensor. I'd also be very surprised if they don't
> make a check for closed throttle when the MAP is indicating low pressure
> and thus calling for more fuel and not rev the engine wildly with a
> closed throttle. Maybe the Chrysler engineers aren't that smart, but
> I'm betting they are.
>
> Have you ever seen a Chrysler engine have a vacuum leak that made it run
> 4,500 RPM with the throttle closed?
>
>
> Matt
>

Matt Whiting wrote:
> maxpower wrote:
>
>> Your right it isnt that nessassary. more of a reference point of open and
>> closed throtlle, u can unhook the tps sensor and the engine will run, it
>> will give a hesitation on take off but will run because the MAP sensor
>> determines load and how much fuel to deliver
>
>
> I don't think Chrysler publishes its ECM algorithms, but I've be very
> surprised if the TPS is used only to sense closed and WOT. If that were
> the case, they would use two cheap switches rather than a relatively
> expensive rheostat sensor. I'd also be very surprised if they don't
> make a check for closed throttle when the MAP is indicating low pressure
> and thus calling for more fuel and not rev the engine wildly with a
> closed throttle. Maybe the Chrysler engineers aren't that smart, but
> I'm betting they are.

Also, with switches, it is a mechanical adjustment (provisions for
adjustment and the labor of doing so) to calibrate the closed and WOT
positions - cost would more than offset the cost of the rheostat. With
a rheostat, the calibrations for the two points are software functions,
and possibly 100% automatic (I would think it would be easy for the
computer, during the learning phase to tell where the throttle closed
position - i.e., the point below which the rheostat never goes), and the
WOT position could be delta'd off of that with acceptable tolerance
stack and variations - though not sure if they actually incorporate such
an Al-Gore-ithm).

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')


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Matt Whiting wrote:
> maxpower wrote:
>
>> Your right it isnt that nessassary. more of a reference point of open and
>> closed throtlle, u can unhook the tps sensor and the engine will run, it
>> will give a hesitation on take off but will run because the MAP sensor
>> determines load and how much fuel to deliver
>
>
> I don't think Chrysler publishes its ECM algorithms, but I've be very
> surprised if the TPS is used only to sense closed and WOT. If that were
> the case, they would use two cheap switches rather than a relatively
> expensive rheostat sensor. I'd also be very surprised if they don't
> make a check for closed throttle when the MAP is indicating low pressure
> and thus calling for more fuel and not rev the engine wildly with a
> closed throttle. Maybe the Chrysler engineers aren't that smart, but
> I'm betting they are.

Also, with switches, it is a mechanical adjustment (provisions for
adjustment and the labor of doing so) to calibrate the closed and WOT
positions - cost would more than offset the cost of the rheostat. With
a rheostat, the calibrations for the two points are software functions,
and possibly 100% automatic (I would think it would be easy for the
computer, during the learning phase to tell where the throttle closed
position - i.e., the point below which the rheostat never goes), and the
WOT position could be delta'd off of that with acceptable tolerance
stack and variations - though not sure if they actually incorporate such
an Al-Gore-ithm).

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')


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http://www.newsfeeds.com The #1 Newsgroup Service in the World! >100,000 Newsgroups
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Much obliged for all the information and tips.


Little more information. The RPMS have settled down into the 3000-3500
range.

There is an opening in the EGR hose that I still need to get fixed.


ERROR CODES:

12- No biggie on this one, the battery was recently disconnected and re-
connected.

24- Throttle Position Sensor

25- Idle Air Control Valve Circuits

I have an Ohm Meter and can check the voltages on them if possible. Not
sure the general procedure or readings, though.

Thanx again.

Much obliged for all the information and tips.


Little more information. The RPMS have settled down into the 3000-3500
range.

There is an opening in the EGR hose that I still need to get fixed.


ERROR CODES:

12- No biggie on this one, the battery was recently disconnected and re-
connected.

24- Throttle Position Sensor

25- Idle Air Control Valve Circuits

I have an Ohm Meter and can check the voltages on them if possible. Not
sure the general procedure or readings, though.

Thanx again.

opening in the EGR hose is a vacuum leak!!!!......keep in mind if this were
a mass air flow system, the vehicle would stall and not run
"Michale" > wrote in message
...
> Much obliged for all the information and tips.
>
>
> Little more information. The RPMS have settled down into the 3000-3500
> range.
>
> There is an opening in the EGR hose that I still need to get fixed.
>
>
> ERROR CODES:
>
> 12- No biggie on this one, the battery was recently disconnected and re-
> connected.
>
> 24- Throttle Position Sensor
>
> 25- Idle Air Control Valve Circuits
>
> I have an Ohm Meter and can check the voltages on them if possible. Not
> sure the general procedure or readings, though.
>
> Thanx again.
>
>

opening in the EGR hose is a vacuum leak!!!!......keep in mind if this were
a mass air flow system, the vehicle would stall and not run
"Michale" > wrote in message
...
> Much obliged for all the information and tips.
>
>
> Little more information. The RPMS have settled down into the 3000-3500
> range.
>
> There is an opening in the EGR hose that I still need to get fixed.
>
>
> ERROR CODES:
>
> 12- No biggie on this one, the battery was recently disconnected and re-
> connected.
>
> 24- Throttle Position Sensor
>
> 25- Idle Air Control Valve Circuits
>
> I have an Ohm Meter and can check the voltages on them if possible. Not
> sure the general procedure or readings, though.
>
> Thanx again.
>
>

now factor in the job the i.a.c does

Matt Whiting wrote:

> maxpower wrote:
>
> > it is the same thing regardless if it is the throttle blade opening or a
> > huge vacuum leak, the MAP sensor determines how much fuel to give it, not
> > the throttle blade. if you disconnected the TPS sensor and opened the
> > throttle blade, the map sensor would compensate for it, thus causing a high
> > RPM The throttle blade does not have anything to do with giving more gas, a
> > carburator would but not this vehicle
>
> Last I knew, the TPS sensor was also factored into the fuel map for ECM
> controlled vehicles. Maybe Chrysler was really stupid with their ECM,
> but I doubt it. If the throttle is closed as indicated by the TPS, then
> I'd be really surprised if the MAP input alone would be enough to
> command fuel be added. If that is the case, then the TPS is completely
> unnecessary.
>
> Matt