I have a 2000 Jeep Grand Cherokee, 4.7 liter engine. 198,000 miles.
Engine has been literally perfect to now.

In the last week, engine has stalled three times, at very slow idle, or very
low speed. I have then noticed that all of a sudden, it is sluggish to
start. Engine turns over real robustly, but takes much longer than normal
to start up.

Engine runs great after start, except for the three stalling occurances in
one week. At normal or high speeds, perfect performance. Good pep. No
noises.

I am not a mechanic, but I suspect a fuel delivery problem. Perhaps fuel
filter or fuel pump ? I have done the ignition switch on and off three
times in sequence, but I get no error code. Just reads "done" after the
third switch.

In this model, is the fuel pump in the gas tank, as is the case with some
Jeeps ? Where is the fuel filter ?

Am I on the right track ?

Any commnents or advice will be appreciated.

James

CranK position Sensor?
Throttle Body?
Coolant Temperature Sensor?

Time to test ign and fuel delivery. ;-)

Just some thoughts!
--
later,
dave AKA vwdoc1
88 XJ 4.0 auto


"James" <no one (AT) bellsouth (DOT) com> wrote

As I said, I am not a mechanic...... but, coolant temperature sensor causes
slow starts and stalls ?

Please elaborate !!

CPS sensor and throttle body problems are valid points I would think...

thanks !!

James
------------------------------------


CranK position Sensor?
Throttle Body?
Coolant Temperature Sensor?

Time to test ign and fuel delivery. ;-)

Just some thoughts!
--
later,
dave AKA vwdoc1
88 XJ 4.0 auto

James wrote:
My first thought is the CPS (Crankshaft Position Sensor). It's job
is to give the computer timing information. Once the engine is running
the computer will "guess" on timing if it has to.

Find the connector that runs back to the CPS sensor and unplug/replug
it a couple of times. Sometimes corrosion will cause a problem, but
they do fail. I've replaced mine once already and it was doign exactly
what you describe.


But before doing that, pull the codes and see what the Jeep knows.
http://www.wjjeeps.com/faultcodes.htm


Fuel delivery problems will cause knocking/sag at "wide open throttle".
Fuel injection is different from the old carb system where engine
vacuum could overcome a failing pump.

The coolant sensor question deals more with long warm-up time.
If you have an ohmmeter they are fairly easy to check. The most I've
ever had to do with mine was clean the connection.

--
-- 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!

Might. On my Chevy I was trying to track down a drivablility problem
and disconnected the temp sensor for the ECM. The engine would barely
start and run with it disconnected. So if it failed in the same
manner as "disconnected" condition it could cause a major problem.

On Sun, 25 Oct 2009 09:33:53 -0400, "James" <no one (AT) bellsouth (DOT) com>
wrote:

Yep what Ashton said. The CTS will tell the ECM what temp the engine is at
so if the CTS tells the ECM that a cold engine is at normal operating
temperature then the fuel will be too lean to easily start that engine.
Some engines can start easier if you disconnect the defective CTS, and some
not at all.

A good engine scanner plugged into the ECM could tell you the coolant
temperature the ECM sees along with other things.

A weak/defective Camshaft Position Sensor could also be the culprit.


"Ashton Crusher" <demi (AT) moore (DOT) net> wrote

Hi James,

I'm not a mechanic either, except for the problems I've corrected on my
Jeep.

Some inexpensive things to consider....

#1. check all vacuum hoses (ouch).
#2. test the TPS with a volt meter (download your TPS version specs)
#3. test the fuel pressure (PSI) from the injector rail.(DL specs)

I really wouldn't think it is the pump because you ARE getting gas,
rather maybe the fuel regulator (chump change) at the rail, or even
upstream by replacing the fuel filter (more chump change).

You'd be surprised at the havoc a malfunctioning TPS (throttle position
sensor) causes.

Ken
1987 Jeep Cherokee / 4.0L / 270k miles

James wrote:

I posted this here on Oct 25, and got **many** helpful replies.

I had the OBD test done, and it showed no errors. Several days after my
first post, the problem seemed to have disappeared. I have now put about
1000 miles on the car, and cranked it close to a hundred times, and it now
cranks perfectly each time. No stalls/ slow idle/ etc.

What gives ? Could I have had a speck of dirt or trash in the fuel filter
and it flushed itself out ? Will the problem likely show up again
tomorrow ?? Is the CPS so weird that it can show intermittant failure,
and seem to be ok for a while ?

My plan (unless I see stronger advice here) is to drive it and enjoy the
ride, and if the problem appears again, to start checking the various
problem areas addressed here.

thanks again everyone !!

James

----------------------------------------------------------------------------
----------



have a 2000 Jeep Grand Cherokee, 4.7 liter engine. 198,000 miles.
Engine has been literally perfect to now.

In the last week, engine has stalled three times, at very slow idle, or very
low speed. I have then noticed that all of a sudden, it is sluggish to
start. Engine turns over real robustly, but takes much longer than normal
to start up.

Engine runs great after start, except for the three stalling occurances in
one week. At normal or high speeds, perfect performance. Good pep. No
noises.

I am not a mechanic, but I suspect a fuel delivery problem. Perhaps fuel
filter or fuel pump ? I have done the ignition switch on and off three
times in sequence, but I get no error code. Just reads "done" after the
third switch.

In this model, is the fuel pump in the gas tank, as is the case with some
Jeeps ? Where is the fuel filter ?

Am I on the right track ?

Any commnents or advice will be appreciated.

James

James wrote:
Keep an eye on the weather.
Quite a few sensor problems crop up when it's hot.

They might have also disconnected/reconnected some of the
harness. That can clean the crudbunnies that build up.

--
DougW

Well, maybe I reported the problem had disappeard too quickly !!

Although the engine still starts perfectly, all of a sudden this morning I
had a very hard time keeping it running at idle. I went through a drive
thru for some coffee, and literally had to recrank it about six times to
make it through. This was only after about a mile of driving from my home.
For the rest of the day it has been perfect.

From my original post, there were many logical suggestions. Two of these
were a possible bad CPS, and possible throttle body problem, perhaps needs
cleaning. Out of these two, which would you suspect more strongly ?

My OP is quoted again below, but keep in mind that it is starting perfectly
now, and has been for about two weeks. After several weeks of running
perfectly, I get this slow idle problem again this morning.

Thanks !!

James

--------------------------------------
I have a 2000 Jeep Grand Cherokee, 4.7 liter engine. 198,000 miles.
Engine has been literally perfect to now.

In the last week, engine has stalled three times, at very slow idle, or very
low speed. I have then noticed that all of a sudden, it is sluggish to
start. Engine turns over real robustly, but takes much longer than normal
to start up.

Engine runs great after start, except for the three stalling occurances in
one week. At normal or high speeds, perfect performance. Good pep. No
noises.

I am not a mechanic, but I suspect a fuel delivery problem. Perhaps fuel
filter or fuel pump ? I have done the ignition switch on and off three
times in sequence, but I get no error code. Just reads "done" after the
third switch.

In this model, is the fuel pump in the gas tank, as is the case with some
Jeeps ? Where is the fuel filter ?

Am I on the right track ?

Any commnents or advice will be appreciated.

James