97 XJ throttle position sensor?

Today, 97 Cherokee, 4.0, manual transmission, 140K miles, failed to start
unless throttle was stepped on just a little. After starting, would not idle
unless throttle was advanced just a little.
Then while driving, if clutch was disengaged and foot off the throttle,
engine would die. If
just a little throttle was held all the time, it would run and drive as if
nothing else was wrong.

I'm guessing tomorrow a new throttle position sensor may be needed. Or what
else??

Thanks for looking!
Old Chief Lynn

Lynn wrote:
> Today, 97 Cherokee, 4.0, manual transmission, 140K miles, failed to
> start unless throttle was stepped on just a little. After starting,
> would not idle unless throttle was advanced just a little.
> Then while driving, if clutch was disengaged and foot off the
> throttle, engine would die. If
> just a little throttle was held all the time, it would run and drive
> as if nothing else was wrong.
>
> I'm guessing tomorrow a new throttle position sensor may be needed.
> Or what else??

Could be, but first check and clean the idle air passage.
http://www.revbeergoggles.com/tb/tb.html

--
DougW

The TPS 'connection' is notorious for having bad connections. We fixed
ours and got almost another ten years out of it before we sold the XJ
when chrysler told us it was 'dead' by simply using a spray contact
cleaner on the plug and socket for it.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00
'New' frame and everything else in '09. Some Canadian Bush Trip and
Build Photos: http://mikeromainjeeptrips.shutterfly.com

Lynn wrote:
> Today, 97 Cherokee, 4.0, manual transmission, 140K miles, failed to
> start unless throttle was stepped on just a little. After starting,
> would not idle unless throttle was advanced just a little.
> Then while driving, if clutch was disengaged and foot off the throttle,
> engine would die. If
> just a little throttle was held all the time, it would run and drive as
> if nothing else was wrong.
>
> I'm guessing tomorrow a new throttle position sensor may be needed. Or
> what else??
>
> Thanks for looking!
> Old Chief Lynn

> Lynn wrote:
>> Today, 97 Cherokee, 4.0, manual transmission, 140K miles, failed to
>> start unless throttle was stepped on just a little. After starting,
>> would not idle unless throttle was advanced just a little.
>> Then while driving, if clutch was disengaged and foot off the
>> throttle, engine would die. If
>> just a little throttle was held all the time, it would run and drive
>> as if nothing else was wrong.
>>
>> I'm guessing tomorrow a new throttle position sensor may be needed.
>> Or what else??
>
> Could be, but first check and clean the idle air passage.
> http://www.revbeergoggles.com/tb/tb.html
>
> --
> DougW

Well, I must admit I was very skeptical about "cleaning the idle air
passage", but after checking the output voltage of the throttle position
sensor, and finding it ok, I pulled the throttle body as recommended
to look at the idle air passage. Yes, it was pretty gunked up, but after
spray cleaning it, I was curious as to what the motor was connected to,
so the idle air motor was removed to see what sort of valve it was, I
encountered more gunk stuck on the nose of the air motor's actuator,
and cleaned it off by scrubbing with cloth and carb cleaner.
Long story shortened: It runs fine now. So, without any new parts,
just cleaning everything up, I hope the fix is permanent.
Only lingering doubt here is that I did disconnect and reconnect the
three electrical connectors on the throttle body devices several times.
Either the cleaning or working the connector contacts has, for now,
solved the problem.
Thanks, Doug and Mike for the advice!

Old Chief Lynn

Lynn wrote:

>
>> Lynn wrote:
>>> Today, 97 Cherokee, 4.0, manual transmission, 140K miles, failed to
>>> start unless throttle was stepped on just a little. After starting,
>>> would not idle unless throttle was advanced just a little.
>>> Then while driving, if clutch was disengaged and foot off the
>>> throttle, engine would die. If
>>> just a little throttle was held all the time, it would run and drive
>>> as if nothing else was wrong.
>>>
>>> I'm guessing tomorrow a new throttle position sensor may be needed.
>>> Or what else??
>>
>> Could be, but first check and clean the idle air passage.
>> http://www.revbeergoggles.com/tb/tb.html
>>
>> --
>> DougW
>
> Well, I must admit I was very skeptical about "cleaning the idle air
> passage", but after checking the output voltage of the throttle position
> sensor, and finding it ok, I pulled the throttle body as recommended
> to look at the idle air passage. Yes, it was pretty gunked up, but after
> spray cleaning it, I was curious as to what the motor was connected to,
> so the idle air motor was removed to see what sort of valve it was, I
> encountered more gunk stuck on the nose of the air motor's actuator,
> and cleaned it off by scrubbing with cloth and carb cleaner.
> Long story shortened: It runs fine now. So, without any new parts,
> just cleaning everything up, I hope the fix is permanent.
> Only lingering doubt here is that I did disconnect and reconnect the
> three electrical connectors on the throttle body devices several times.
> Either the cleaning or working the connector contacts has, for now,
> solved the problem.
> Thanks, Doug and Mike for the advice!

Amazing how much gunk builds up in that port, isn't it? You likely got the
shaft behind the pintle cleaned while you were at it, but the drive shaft
going into the motor can get gummed up, too. Just spray that with carb or
brake cleaner - don't try and remove it!

I can't remember about the later models, but on my 88 there is a second
bypass port in the driver's side wall of the throttle body - about 1/3 of
the way around from the IAC port. Mine was so plugged up when I got the
Jeep that I had to resort to drill bits to cut it loose enough enough to
get solbent into the hole. There is a needle at the bottom of the shaft
that is covered by a plug on mine - pop the "tamper-proof" plug out then
count turns as you bottom the needle (all the way in). Write it down, then
remove the needle valve to get a cleaning rod down past the needle shaft.
Took me a good while to get that clean but it was the final step in getting
a proper idlw with that old Renix system. Re-install the needle valve,
seat it all the way in, then back out the number of turns you wrote down.

--
Will Honea

Lynn wrote:
>> Lynn wrote:
>>> Today, 97 Cherokee, 4.0, manual transmission, 140K miles, failed to
>>> start unless throttle was stepped on just a little. After starting,
>>> would not idle unless throttle was advanced just a little.
>>> Then while driving, if clutch was disengaged and foot off the
>>> throttle, engine would die. If
>>> just a little throttle was held all the time, it would run and drive
>>> as if nothing else was wrong.
>>>
>>> I'm guessing tomorrow a new throttle position sensor may be needed.
>>> Or what else??
>>
>> Could be, but first check and clean the idle air passage.
>> http://www.revbeergoggles.com/tb/tb.html
>>
>> --
>> DougW
>
> Well, I must admit I was very skeptical about "cleaning the idle
> air passage", but after checking the output voltage of the throttle
> position sensor, and finding it ok, I pulled the throttle body as
> recommended to look at the idle air passage. Yes, it was pretty gunked up, but
> after spray cleaning it, I was curious as to what the motor was
> connected to, so the idle air motor was removed to see what sort of
> valve it was, I encountered more gunk stuck on the nose of the air
> motor's actuator, and cleaned it off by scrubbing with cloth and carb
> cleaner. Long story shortened: It runs fine now. So, without any
> new parts, just cleaning everything up, I hope the fix is permanent.
> Only lingering doubt here is that I did disconnect and reconnect
> the three electrical connectors on the throttle body devices several
> times. Either the cleaning or working the connector contacts has,
> for now, solved the problem.
> Thanks, Doug and Mike for the advice!
>
> Old Chief Lynn

Not a problem. Spraying the TB and cleaning around the butterfly should
be routine maintenance. I clean mine about twice a year.

Just a bit of obstruction on that valve and the engine will run rough at
idle. When it gets plugged or the area around the butterfly builds up
enough crud the engine will stall at idle. The key was you having to
keep a bit of pedal on to maintain running. There is a tiny hex screw
on the TB just behind where the throttle cable goes on. You shouldn't
ever have to mess with that. But if the IAC motor goes, you can turn that
in to set the base idle. Adjusting it with a good IAC motor just changes the
motors operational range. Sometimes a 1/8 turn in will smooth out a worn
motor.

If the passage had a lot of junk it it then you should look at the CCV system.
Jeeps don't use the old PCV, they use vac to draw crankcase fumes into the engine.
When the rear vent starts to plug up the forward vent will draw into the airbox
and then down into the TB. That's where the oil buildup comes from.

http://jeep.off-road.com/jeep/articl....jsp?id=257985
I'll caution you, the gromets and plastic bits are a real pain. I
had to go fishing into the valve cover to retreive part of one that
broke off.

--
-- DougW -- 93 ZJ 4.0 http://revbeergoggles.com
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
Banks Header - and BEER, in the fridge!