lucica

Good afternoon all...

I am writing from Guatire Venezuela.
I am an old reader of this forum, but just today I have registered in order to post a comment about my cherokee classic that is making me crazy

The issue happens in this way :

I can start up the cherokee , but a few seconds later, the engine goes off vertically (stalling ???) : no misfire, no check gauges alarm in the dash control, no warning in the dash control after the start up ( or during the few time ON)

If I want to keep the engine ON, I need the RPM high (about 2000 rpm) , it means, I need to keep the gas pedal

...what I have done or checked until today ???
1) battery is new
2) all negative and -12 V cabling related to battery , starter and alternator were replaced by a new better one ( no ties, better gauge cabling)
3) starter and alternator were reviewed 3 or 4 months ago by maintenance.
4) the MAIN GROUND cabling that connects the engine (block) with the firewall was replaced by a new better one
5) IAC sensor and throtle system were cleaned
(initially, the engine turned OFF specially passing from one shift to the next : i.e. 1st to 2nd, 2nd to 3rd. After clean the IAC and the Throtle system the issue improved. Later, unfortunately the situation became worst)
6) I took the cherokee to the scanner (mechanic's home) and the result was passed with no error codes. Despite that, other sensors were swapped to check the result : MAP, CPS. No success. Also, fuel pump pressure was measured and according with the comment of the mechanic, the pressure was in the correct levels ( I donīt remember the result)

According with the comment of the mechanic, 2 more points can be related with this issue : Ignition coil pack(ICP) or ECU

I was reviewing on internet and I tried with the ICP in the following way:
I have measured the ohms (by pairs 1&6 , 2&5 , 3&4) ) and the reading of all three pairs are around 15 KΩ. ( I think this is OK or it is a typical value) Then, I measured every coil with the remaining coil different to his pair, (i.e. 1 with 2&5 and 1 with 3&4), and the result is about 0.3 MΩ...not OL (not totally open)


....does anyone knows if the ICP can cause this kind of issue ???
....does anyone knows if the ICP can be tested with a multitester in this way ???
...another idea to discard if the ICP is root cause ???

Any idea, suggestion o comment will be very appreciated.
( sorry if my english sometimes is not so technical as well as it is needed here )

Gracias


Saludos

CCKen

Here's a way to test the coil rail:

lucica

Thanks a lot CCKen.


I understand that if only one primary coil result is out of range, the ICP should be replaced. But, only one coil out of range can cause that the engine goes off few seconds after was turned on ???

I am going to test according with the note and I will let you know
(if the 3 coils are defective is a very bad luck )

Gracias

Saludos

lucica

Hi CCKen....

I have measured the 3 coils according with the table sent earlier.
For all cases, the result was about 1.1 Ohm (tester 1) or 1.4 Ohm (tester 2)
( a little bit higher than the maximum value 0.88 ohms )


For all measures, the result exceeds more than 20% of maximum.

....should be replaced the ICP ???
...according with this test, the 3 coils are defective ???

(if we follow truly the values shown in the table, we would conclude that the ICP has to be replaced)

Despite this, the cherokee is capable to start up....

Gracias

Saludos

CCKen

Do you have the Sentry Key Immobilizer System?

lucica

Hola CCKen....

Thanks for your help.

Yes, my cherokee came from the factory with the Sentry Key Immobilizer System (SKIS).To be in the same page, I understand that this system it is one that consists of the ignition key by itself and another additional key with 2 buttons : lock and unlock remotely. ( not including panic button)

I have read that this system also can cause issues after the engine has been turned on, but really speaking, I donīt know how to test it.

Addtional to the SKIS, the cherokee came from the factory with one additional system alarm : BUNKER alarm.

Being honest, I only use the ignition key to start up the car.
Then, I let the bunker alarm to arm and close the doors seconds later that the cherokee is power off, I mean, I almost don't use the lock and unlock of the SKIS


Gracias

Saludos

CCKen

Those values in the table are at room temperature (around 68-70*F). They are the values stated in the Factory Service Manual.


If the coil rail was not 'room temp' when the resistance readings were taken, you may want to try it again.


I wouldn't want to condemn the coil rail if all three readings are the same; albeit, a bit high.

CCKen

Do you think that "Bunker alarm system is causing the shut-down. I think it might be. Can you disarm it somehow?


SKIS does not lock and unlock your doors, the remote keyless entry system dos that (the Fob with the two buttons).

lucica

Hi CCKen....

Regarding the ICP tests, I agree with your comment:
"I wouldn't want to condemn the coil rail if all three readings are the same; albeit, a bit high" ( the measures were taken with the coil rail cold and the temp was about 82°F)

Gracias

Saludos

lucica

Now, that I have a new battery, I am going to try to "by-pass or disarm" the Bunker alarm. To be honest, I am scared about it....
As far as I know, this bunker alarm uses 2 relays : one relay to inhibit the alarm and the 2nd one is related to signals to dash control (I guess)
Also, the cherokee includes an external button to inhibit the alarm, I mean, once this button is pressed, does not activate the doors alarm once they are closed ( I will try this button first .....)

2 weeks ago, seems that the engine wouldn't start up due to bunker alarm system but on that moment, the battery was defective
(with defective battery, the bunker system alarm is unpredictable)

Let me try tomorrow and I am going to let you know.

Gracias


Saludos

lucica

Hola CCKen....


Today, I have done some tests to check the BUNKER alarm and the cherokee status

As I wrote yesterday, this alarm can be inhibited (disarmed) by one button.
I did it in this way, but after test, the behaviour was the same.

After this, I tested disconnecting the 2 relays involved to the BUNKER alarm module
(1 relay controls doors lock/unlock and the 2nd one I understand is to block the engine)
No success after test

Bunker module is located below the wheel and the installation could have been performed in a better way
Because of this, I decided to disconnect the plugs , clean the field connections with SQ cleaner
and re-connect back all the plugs in the module.
After this, I started the cherokee and was ON more than 25 minutes with no shut-down
I tried the same about 5, 6 times and only one time the cherokee was shut down as before
Still, the alarm wiring harness is not properly ordered.
(thatīs why I wrote yesterday that I was scared to "touch this")


Being honest, I haven't fix the issue and still I don't know what really happens.
Anyways, the status has improved from the point of view that I can start up the cherokee and is
not shut down after make some "cleaning" in Bunker module alarm.
Also, looks like we have confirmed that the ICP was not the issue, so, I
don't need to buy it so far


What I have noted today is that I need to try 2 or 3 times to start up the engine.
Anyways, the fuel level is a little bite low currently....
(looks like I am in more than one problem ......ja ja ja)

Tomorrow, I am going to ride a little bit to test

I appreciate your comments.

Gracias

Saludos

CCKen

Good luck.

lucica

Hi CCKen and others Jeepers ....Happy 2016 for all...

Regarding this issue ("chicharron=pork rind or cangrejo=crab" as we call it in spanish) ,today I changed my mind and I went to the gas system.
Because I haven't a gas pressure meter, I decided to check the status of the gas tank and pump (conections, dirty, others)

After releasing connections, I could note that the line coming from the rollover valve (EVAP CANISTER VENT LINE), was poorly retained , because when I did pressure to release in the opposite side of the pump, the pipe was hanging on my hand.

I am not sure if this is the cause, but I think that this kind of poor connection will not improve the performance of the fuel system

I hope to complete the tank removal this weekend and check and re-assembly any wrong connection. Also check the status of the gas pump.

Thanks...

Saludos

lucica

Hi CCKen, good night....

In my last post, I wrote that I found something wrong near to the fuel pump. Really the thing was that the line related to EVAP was no properly tied.

After that, I made the next tests :

1) I made a fuel pump tester and if I drain totally the line, I need to put the switch ON 3 times to reach 50 psi
1st= 20 psi, 2nd=35 psi , 3rd=+/- 50psi
2) If I start ON the cherokee and hold the gas pedal to keep 1500/2000 rpm (to keep the engine ON) , the fuel pressure is very stable about 50 psi
3) If I start off the switch ( or if I release the gas pedal and the cherokee goes OFF), the pressure down about 1~2 psi at that moment (48 psi)
4) Keeping the gas pressure conected ( and the engine OFF), 10 minutes after, the gauge indicates about 34 psi ( - 14psi) , and 10 minutes later the gauge shows 26 psi. It means, in 20 minutes, the psi went down about 24 psi
5) I have 2 IAC : original one MOPAR , second one made in china may be.
( I do know that these kind of parts has to be used only MOPAR but the second one is a borrowinf from a friend to make tests)
The MOPAR IAC, indicates 53 ohms in each coil.
I tested the mopar IAC sensor connected to the harness but out of the throtle body and putting the key ON ( without starting the engine) and the IAC comes out.Unfortunately, the IAC stem was released totally. I could re-assembly the sensor.

6) If I start the engine and disconnect the map sensor, the engine keeps ON
( of course, the check engine goes ON inmediatly)
I swapped my map sensor with another cherokee, and the 2nd cherokee starts OK and keeps the engine working fine.

Finally, today I cleaned the throtle body and I could drive fine about 10 minutes . Then , I put full the gas tank and the issues started again.
( at that moment, the cherokee was at working temperature)

7) Battery is new. But, 2 days ago, I was doing many tests (starting the engine ON many times) and after that I needed to charge the battery. Now, the battery indicates 12.5 volts with no loading and about 50 mAmps with the system connected. Once the engine is ON, the voltage goes about 13,85 volts


So, after the tests done :

a) could I suspect that there is any issue with the fuel pump ???
b) could I suspect that the issue would be related to IAC ???

Thanks CCKen.

Gracias

Saludos

lucica

Good afternoon all....

Finally, I could find the issue after a lot of tests :
The problems were caused by the ICP : ignition coil pack.

One week ago I did buy a new one and I replaced. Then, the cherokee
start to work properly.
It is amazing how a bad ICP can influence in the performance of the vehicle:
Months ago, when this issue started, also there was some kind of"shaking" when i passed to 5th gear. Now, after replaces the ICP, the cherokee rides properly in 5th gear.
Also, looks like the cherokee response at the moment to changes gear is very very better.

Thanks to all for the suggestions sent...

Gracias

Saludos