90 XJ AT shifting / TPS problem

Hello All, My XJ starting shifting weird the other day, sometimes it
couldn't figure out what gear it wanted to be in and sometimes it
wouldn't shift out of 2nd. The same thing happened 4 yrs ago and a new
TPS fixed it.
I cleaned connections and then replaced the TPS, it was fine for a day
and then it acted up again and the idle was up to 2500
I checked voltage at the square plug (to AT) and it is way off.

Connection A (input) reads 4.32v should be aprx. 5v
Connection B (output) reads .34 should be 82% of A or 3.5v
Connection D (Ground) reads .8v should be less than .1v

The one I replaced had a higher output of .5v

Do you think the new one is bad already?

http://www.transonline.com/transdige...ers/index.html
God Bless America, Bill O|||||||O
http://www.billhughes.com/

wrote:
>
> Hello All, My XJ starting shifting weird the other day, sometimes it
> couldn't figure out what gear it wanted to be in and sometimes it
> wouldn't shift out of 2nd. The same thing happened 4 yrs ago and a new
> TPS fixed it.
> I cleaned connections and then replaced the TPS, it was fine for a day
> and then it acted up again and the idle was up to 2500
> I checked voltage at the square plug (to AT) and it is way off.
>
> Connection A (input) reads 4.32v should be aprx. 5v
> Connection B (output) reads .34 should be 82% of A or 3.5v
> Connection D (Ground) reads .8v should be less than .1v
>
> The one I replaced had a higher output of .5v
>
> Do you think the new one is bad already?

Hello Bill, I took a look at that info earlier today. His diagram of
the TCU is 180 out from mine.I did check the fuse, cleaned the
connector and verified 12v to the TCU. I figure since I do have decent
input voltage to the TPS and the output is way off it has to be a bad
TPS . The only thing between the input voltage and the output voltage
is the TPS internals, unless I'm wrong which happens alot (that's why I
posted)

The Throttle Position Sensor is like a mechanical kick-down rod and
lever, if it's bad the transmission still shifts normally, but like for
normal acceleration.
God Bless America, Bill O|||||||O
http://www.billhughes.com/

wrote:
>
> Hello Bill, I took a look at that info earlier today. His diagram of
> the TCU is 180 out from mine.I did check the fuse, cleaned the
> connector and verified 12v to the TCU. I figure since I do have decent
> input voltage to the TPS and the output is way off it has to be a bad
> TPS . The only thing between the input voltage and the output voltage
> is the TPS internals, unless I'm wrong which happens alot (that's why I
> posted)

The TPS on my XJ has 2 pigtails one sends a voltage signal to the
transmission controller. The spec for the TPS output to the
transmission controller is about 4v, if it's only putting out .34v
wouldn't that affect the tranny? I had the same problem 4 yrs ago and a
new TPS was the fix.

Thanks, JK

Your readings don't sound right to me...

With the engine off and the key on run, the AC off, you should see a
0.026 volts. When you open the throttle all the way, you should see 4.8
volts.

The TPS for the auto should have the second output which should be the
inverse of the above readings as far as I know. 4.8 V at the idle
position and 0.02 V full open.

You also can take an ohm meter and read it as the throttle opens. It
should change smoothly. If it is jerky, the coil inside the TPS is
dirty or bad.

On your 90, I think the TPS is adjustable for the bottom end or the .02
volts. There should be a capped screw like a mix screw on a carb.

I have been told you can actually clean the guts of the TPS, but haven't
needed to yet.

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:
>
> Hello All, My XJ starting shifting weird the other day, sometimes it
> couldn't figure out what gear it wanted to be in and sometimes it
> wouldn't shift out of 2nd. The same thing happened 4 yrs ago and a new
> TPS fixed it.
> I cleaned connections and then replaced the TPS, it was fine for a day
> and then it acted up again and the idle was up to 2500
> I checked voltage at the square plug (to AT) and it is way off.
>
> Connection A (input) reads 4.32v should be aprx. 5v
> Connection B (output) reads .34 should be 82% of A or 3.5v
> Connection D (Ground) reads .8v should be less than .1v
>
> The one I replaced had a higher output of .5v
>
> Do you think the new one is bad already?

Your 90 I think has a RENIX system and the TPS is adjustable. Have you
adjusted it? Also as I recall the readings for a auto are different but I
don't remember for sure.

JoBo

> wrote in message
oups.com...
> Hello All, My XJ starting shifting weird the other day, sometimes it
> couldn't figure out what gear it wanted to be in and sometimes it
> wouldn't shift out of 2nd. The same thing happened 4 yrs ago and a new
> TPS fixed it.
> I cleaned connections and then replaced the TPS, it was fine for a day
> and then it acted up again and the idle was up to 2500
> I checked voltage at the square plug (to AT) and it is way off.
>
> Connection A (input) reads 4.32v should be aprx. 5v
> Connection B (output) reads .34 should be 82% of A or 3.5v
> Connection D (Ground) reads .8v should be less than .1v
>
> The one I replaced had a higher output of .5v
>
> Do you think the new one is bad already?
>

Hello, yes I adjusted it, it won't adjust near far enough to get a
proper reading. The readings from the AT plug are .35v at idle and .01v
wide open. The readings while opening throttle are smooth. The ground
reading of .8v has me thinking I should splice a ground to the circuit,
this was recommended in another post. I did check chassis to block
grounds and I did the old jumper cable check with no change in reading.
Thanks, JK

Well I guess it's not the TPS, just put in another new one and get the
same readings. Could the TCU affect the output voltage of the TPS?

I pulled the fuse from the TCU and it shifts fine manually, also took
some readings at the TCU and they are way off. I guess a bad TCU? The
link that Bill gave has some great info on checking the TCU but I was
looking at it backwards and thought it was 180 out. The guy also says
at the end that if the readings are within spec the TCU is a
transmission condemed unit, I'm thinking he meant out of spec.