Throttle Position Sensor and....

My 1994 Cherokee 4.0 was kicking out a code 24..TPS..It was running a
bit erratic..hesitant..etc....Went to the junkyard and found another
one and cleared the code...Ran perfectly for 200+ miles and then the
code and minor troubles returned.....Back to the junkayrd..Found a 1996
4.0 with only 72,000 miles on it (Whole side caved in from a wreck near
the rear) got that sensor..Same thing..Ran great for several days then
code 24 again...All these sensors can`t be bad...What else could cause
that code to appear if the sensor is ok?...Or what could cause sensors
to go bad that fast if in fact they are bad?...I read the Haynes manual
about checking the sensor and it says to "back probe" (A few posters
also mention this) what exactly does that mean?...Thanks

Used parts, why not get a new one and eliminate the posssibility of that
being the problem. Go to autozone.com/repairinfo for the testing of a tps on
that truck.
> wrote in message
ps.com...
> My 1994 Cherokee 4.0 was kicking out a code 24..TPS..It was running a
> bit erratic..hesitant..etc....Went to the junkyard and found another
> one and cleared the code...Ran perfectly for 200+ miles and then the
> code and minor troubles returned.....Back to the junkayrd..Found a 1996
> 4.0 with only 72,000 miles on it (Whole side caved in from a wreck near
> the rear) got that sensor..Same thing..Ran great for several days then
> code 24 again...All these sensors can`t be bad...What else could cause
> that code to appear if the sensor is ok?...Or what could cause sensors
> to go bad that fast if in fact they are bad?...I read the Haynes manual
> about checking the sensor and it says to "back probe" (A few posters
> also mention this) what exactly does that mean?...Thanks
>



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Shep wrote:
> Used parts, why not get a new one and eliminate the posssibility of that
> being the problem.

Maybe I don`t want to pay $80 for a part I don`t need..I get the
sensors for free and it`s something that getting a used one shouldn`t
be a problem with it being good..Thanks for the non-answer

The usual problem I see with the TPS and the CPS is just a dirty
connection plug. I take spray contact cleaner to them and then they
work perfect again. So far 'I' have not needed to change either.

I just got an 87 Cherokee and it wanted to rev at 2300 every second time
it was starter. It needed a new TPS.... Ya sure it did. One quick
spray of the connection with contact cleaner and it purrs at 650 rpm.

I was told 6 or 7 years ago I needed a new TPS for my 88 Cherokee which
now has 315K km. Again, a spray on the connection every two years or so
and it is still running perfectly with the original TPS in there.

They are low power computer signal connections. They can be corroded
enough to still look clean but not pass the signal. A fresh plug and
unplug will scratch a new contact for a very short while sometimes, but
the clean is the best. That is why folks say to unplug and plug back
the CPS to get a few more starts out of them...

Oh, 'back probing' just means poking a meter into the back side of a
live connection to try and get a voltage reading out of it. TPS voltage
should be from 0.02V at idle position up to 4.8V at the full throttle
position with the engine and AC off but the key in 'run'. The TPS can
be tested unplugged with an ohm meter. It is a rheostat that should
have even resistance all the way up. If the resistance jumps around it
is a bad or dirty one.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

wrote:
>
> My 1994 Cherokee 4.0 was kicking out a code 24..TPS..It was running a
> bit erratic..hesitant..etc....Went to the junkyard and found another
> one and cleared the code...Ran perfectly for 200+ miles and then the
> code and minor troubles returned.....Back to the junkayrd..Found a 1996
> 4.0 with only 72,000 miles on it (Whole side caved in from a wreck near
> the rear) got that sensor..Same thing..Ran great for several days then
> code 24 again...All these sensors can`t be bad...What else could cause
> that code to appear if the sensor is ok?...Or what could cause sensors
> to go bad that fast if in fact they are bad?...I read the Haynes manual
> about checking the sensor and it says to "back probe" (A few posters
> also mention this) what exactly does that mean?...Thanks

wrote in article
om>...
> My 1994 Cherokee 4.0 was kicking out a code 24..TPS..It was running a
> bit erratic..hesitant..etc....Went to the junkyard and found another
> one and cleared the code...Ran perfectly for 200+ miles and then the
> code and minor troubles returned.....Back to the junkayrd..Found a 1996
> 4.0 with only 72,000 miles on it (Whole side caved in from a wreck near
> the rear) got that sensor..Same thing..Ran great for several days then
> code 24 again...


Just remember, there is a reason why they are called "junk" yards......


> All these sensors can`t be bad...What else could cause
> that code to appear if the sensor is ok?...Or what could cause sensors
> to go bad that fast if in fact they are bad?...

Not having your vehicle right in front of me, I would suspect that you are
fixing the symptom....not the cause.


> I read the Haynes manual...

THAT could easily be a part of your problem.....



> about checking the sensor and it says to "back probe" (A few posters
> also mention this) what exactly does that mean?...

That means to check back through the system to see if something upstream is
breaking/burning up these TPS units...

How dare you not fix his used parts/car problem!!
"*" > wrote in message
news:01c693cc$b02d2d40$dc92c3d8@race...
>
>
> wrote in article
> om>...
>> My 1994 Cherokee 4.0 was kicking out a code 24..TPS..It was running a
>> bit erratic..hesitant..etc....Went to the junkyard and found another
>> one and cleared the code...Ran perfectly for 200+ miles and then the
>> code and minor troubles returned.....Back to the junkayrd..Found a 1996
>> 4.0 with only 72,000 miles on it (Whole side caved in from a wreck near
>> the rear) got that sensor..Same thing..Ran great for several days then
>> code 24 again...
>
>
> Just remember, there is a reason why they are called "junk" yards......
>
>
>> All these sensors can`t be bad...What else could cause
>> that code to appear if the sensor is ok?...Or what could cause sensors
>> to go bad that fast if in fact they are bad?...
>
> Not having your vehicle right in front of me, I would suspect that you
> are
> fixing the symptom....not the cause.
>
>
>> I read the Haynes manual...
>
> THAT could easily be a part of your problem.....
>
>
>
>> about checking the sensor and it says to "back probe" (A few posters
>> also mention this) what exactly does that mean?...
>
> That means to check back through the system to see if something upstream
> is
> breaking/burning up these TPS units...
>
>



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Shep wrote:>>> How dare you not fix his used parts/car problem!!<<<

I didn`t want someone to fix it for me but to answer some basic
questions in a clear logical manner which Mike and many others always
have..In his above post he explained "back probing" which is what I
thought it may have been and which I am completely competent to do but
I had never heard that phrase before...I also asked what else could be
causing the problem other than the sensor and he suggested another
possiblity..It may not be the cause but it`s something else to
consider...As far as vehicles in junkyards having "junk" parts that
simply isn`t true as I`ve used them for 25 years and have saved
thousands of dollars by getting used but still fully functional factory
parts off of "junk" cars instead of buying new after-market
parts...Alternators..starters..wiper motors..fans..etc...I mean
seriously..Who is going to take a Jeep to the junkyard because the TPS
is bad???.......Thanks for all the useful tips and advice I get on here
from time to time :-)

Mike Romain > wrote in
:


>
> Oh, 'back probing' just means poking a meter into the back side of a
> live connection to try and get a voltage reading out of it.



Some connectors are very hard to backprobe with the meter, as the connector
conforms closely to the wire diameter. In those cases, I use a straightened
paper clip to stick into the connector and make contact with the metal
contact inside, then touch the VOM probe to that.




> TPS voltage
> should be from 0.02V at idle position



Are you sure it isn't more like 0.2V? 0.02 seems kinda low.



> up to 4.8V at the full throttle
> position with the engine and AC off but the key in 'run'. The TPS can
> be tested unplugged with an ohm meter. It is a rheostat that should
> have even resistance all the way up. If the resistance jumps around it
> is a bad or dirty one.


Comboverfish told me that wasn't a reliable way to check, when I needed to
check mine. He said voltage was the only reliable way.


--
TeGGeR®

"TeGGeR®" wrote:
>
> Mike Romain > wrote in
> :
>
> >
> > Oh, 'back probing' just means poking a meter into the back side of a
> > live connection to try and get a voltage reading out of it.
>
> Some connectors are very hard to backprobe with the meter, as the connector
> conforms closely to the wire diameter. In those cases, I use a straightened
> paper clip to stick into the connector and make contact with the metal
> contact inside, then touch the VOM probe to that.

I have used needles and then sealed the holes with a dab of sensor safe
RTV.

>
> > TPS voltage
> > should be from 0.02V at idle position
>
> Are you sure it isn't more like 0.2V? 0.02 seems kinda low.

The Jeep one calls for >200 MV or .02V. The early adjustable ones
called for 0.026V.

If it's an automatic, it actually works backward on one pin set. 4.8 at
idle and 0.02 at full throttle.

>
> > up to 4.8V at the full throttle
> > position with the engine and AC off but the key in 'run'. The TPS can
> > be tested unplugged with an ohm meter. It is a rheostat that should
> > have even resistance all the way up. If the resistance jumps around it
> > is a bad or dirty one.
>
> Comboverfish told me that wasn't a reliable way to check, when I needed to
> check mine. He said voltage was the only reliable way.

I wouldn't argue there, but if the TPS has a 'dead' spot in the
acceleration, that can usually show up on the resistance.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

Mike Romain > wrote in
:

> "TeGGeR®" wrote:
>>

>>
>> > TPS voltage
>> > should be from 0.02V at idle position
>>
>> Are you sure it isn't more like 0.2V? 0.02 seems kinda low.
>
> The Jeep one calls for >200 MV or .02V. The early adjustable ones
> called for 0.026V.



A millivolt is 1/1000th of a volt. A thousand of them is 1V. If you had
only 200 of them, that would be .2 of a volt, not .02.

Work the decimal places back and you'll see:
1.000 V (1,000 millivolts)
0.200 V (200 millivolts)
0.020 V (20 millivolts)



>
> If it's an automatic, it actually works backward on one pin set. 4.8
> at idle and 0.02 at full throttle.



My Integra's is .3V to 4.5V through its range, from closed to WOT.



>
>>
>> > up to 4.8V at the full throttle
>> > position with the engine and AC off but the key in 'run'. The TPS
>> > can be tested unplugged with an ohm meter. It is a rheostat that
>> > should have even resistance all the way up. If the resistance
>> > jumps around it is a bad or dirty one.
>>
>> Comboverfish told me that wasn't a reliable way to check, when I
>> needed to check mine. He said voltage was the only reliable way.
>
> I wouldn't argue there, but if the TPS has a 'dead' spot in the
> acceleration, that can usually show up on the resistance.



That's what I thought too, but he differed and he's got a lot more
experience than I do, so I checked it his way. It tested OK either way.


--
TeGGeR®