newXJer

I'm new to the forum but have done a lot of reading and researching. I recently purchased a 2000 Cherokee sport 4.0 inline6 engine with 156k miles. Problems started with the common no start issue. So being new to the Cherokee I turned to this forum and found the common issue of the crankshaft position sensor. I purchased and replaced the sensor and she started back up. But then it was spitting and sputtering in idle and I got more codes with those being; O2 sensors, misfires of coil packs A,B,C. So I replaced the coil pack with brand new And replaced both o2 sensors. Still rough idle. If I leave the vehicle idle long enough it will die. But starts right back up no matter the temp of the engine. Once I put it in gear the sputter goes away and runs fine other than poor mpg. Today check engine light came back on, as I new it would (came on while in park with engine at idle....idles around 700-800 rpms). Hooked up scan tool and gave me code of p1391- Intermittent loss of CMP or CKP (Cam or Crank position sensors). That being said I have already replaced the camshaft sensor and adjusted the timing with piston 1 being at TDC and the toothpick method for syncing the camsyncronizer. I can let vehicle idle it will start to sputter then I unplug the camshaft sensor and the sputter goes away. The second I plug it back in it starts to sputter again. Just curious as to what others think my next step should be?? Am i looking at I timing chain issue? I did rotate the camsensor and synchronizer like you would turn a distributor And it smoothed out the idle a bit but it still sputters. Also could this be a reason for poor gas mpg?

tjwalker

Where did you buy your crank sensor? And your cam sensor? It is not at all unusual to have problems with aftermarket crank sensors. Because of this, I buy this sensor ONLY from the Jeep dealership.

If you continue to get a P1391, you need to continue to concentrate on the cam and crank sensor circuits. Be sure that all connectors for those sensors are cleaned with electrical contact cleaner and add a dab of dielectric grease to the connectors before reconnecting.

If you get stuck, I recommend a Mopar crank sensor.

newXJer

I purchased the crank sensor from oreillys as it was the only store that had one in stock and the camsensor came from NAPA.

newXJer

Other things I have done just as a side note are remove idle air controller, cleaned throttle body and butterfly valve with throttle body cleaner. Poured seafoam into gas tank. Checked for vacuum leaks...didn't find any. Checked pressure in valves all being around 150psi. Put in brand new spark plugs.

newXJer

Removed and cleaned iac that is.

newXJer

I guess another question would be why does this problem only throw a code when in park and idling not when I'm at crushing speeds or the rpms are up??

newXJer

Well for anyone that is interested. I replaced the crankshaft position sensor. The CPS I took out was a masterpro from oreillys. I went to napa and bought a echlin CPS. Cleared all my problems up and running great now.

tjwalker

Glad we could help.

There are some total crap aftermarket crank sensors floating around out there.

newXJer

I guess so. And that was the third one I had out in so I was really on the fence about getting yet another one and to have the same results. But I bit the bullet and so far so good!

tjwalker

I buy my crank sensors ONLY from Jeep, but to be fair.....I haven't heard anything negative about the Echlin sensor at Napa.

One of the problems with some of these aftermarket crank sensors is that there can be a problem with the correct "spacing" of the sensor. As this is a hall effect sensor, spacing is critical. And if you are lucky enough to get one of these gems, they may test out as electrically good, but not work or work poorly when installed. Adds to the confusion as many people will get tunnel vision and rule the crank sensor out as a possible cause once they have installed a new one. I've seen multiple threads with this exact situation and yours is another one to add to the pile.

One thing I do know. You will get a quality crank sensor with the correct spacing if you buy MOPAR. I just paid about $60 (moparonlineparts) for one for my 99.

Buyer beware.

jbossnack

NewXJer - did your engine seem to run just fine if you would drive around and keep the RPM's over 1,000 ? Mine starts up great but when the idle comes down to 750 it starts to shake and misfire and if left long enough at idle in park, it will almost stall and die. I've had it die several times in a parking lot when backing up and turning my wheels. Then it's really hard, almost like it's been flooded. Here is a video of my vehicle on YouTube: (I also posted a 2nd video after it warmed up)

TJ,

I'm about to order myself a new CPS. I've been on MoparOnlineParts.com RockAuto.com and NAPAonline.com looking for CPS.

At MoparOnlineParts.com I search for a 1999 Jeep Cherokee and I get this below:

Powertrain control, Crankshaft position sensor
Jeep, Manual Trans
ELECTRICAL »Powertrain control
Jeep › Cherokee XJ › 1997-1999
$74.25
Your Price : $51.23

However, I've got a AW4 Automatic transmission. This part says it's for a manual transmission.

Is that going to be a problem?

Good news is that the MoparOnlineParts.com is actually cheaper than NAPAonline.com BUT the OEM part available on RockAuto.com is an OMIX-ADA part that is 3x the price of other two places.

So, what make and model # do you use for your CPS?

It's confusing trying to find the best "OEM" part.

Thanks guys!

John

newXJer

Yes with the masterpro crank sensor my '00 Cherokee would start fine, in park would idle around 750-850 rpms and would act like it was misfiring. Once I put in gear and got on the road the jeep ran fine. I would get to my destination and put in park then engine light would come on with the p1391 code.

I went through 3 crank sensors had the same problem with all of them until I went to napa yesterday and got one from them.

NAPA
Crankshaft Sensor
Part Number: ECH CSS638
Product Line: Echlin Ignition Parts

Paul Forrest

I changed my crank sensor and it ran bad so I noticed no paper on the bottom of the sensor so I put a slice of tape on the sensor I guess it was to close after that I reinstalled it jeep ran great

Jeepsurgeon

1996 jeep cherokee P1391 does not necessarily mean cam or crank sensor is non funtioning
more times than not it is a power supply problem
chaffed, grounded or open wiring somewhere in the circuit
battery, ignition, Fuse link, fuse box, ASD relay, pcm
then if all those have good continuity and resistance checks
Check pcm to field excitation 12 volts at the alternator
the voltage regulator is inside the PCM therefore it is not adjustable
I ran a voltage check on the alternator power out where I noticed it was only putting out 12.4 volts of current
I pulled the alternator and found it had worn brushes on their last legs.
I replaced the brushes and reassembled the alternator
which now puts out a healthy 14.8 volts.
it's important that the alternator operates correctly
Because all loads to the PCM are supplied via the alternator output , the battery is slowly recharged by excess voltage over 12.6 volts since the old output was 12.4 the battery was slowly drainingThe 2 brushes inside the alternator were charging intermittently
My P1391 was.immediatly cleard up and went from stalling,and stumbling and backfiring through the intake to a steadiy
purr. The set of brushes cost $4.98 from Napa .A marginal alternator putting out 12.4 volts will not even trip a gen light
warning or put out a code.If your alternator is not putting out at least 13 volts
Dont assume it's the alternator automatically
It could be the field excitation current from the PCM or bad diodes orr worn brushes.This intermittant power surge and drop caused surging power in the PCM which was affecting the power source to the crank and cam sensors causing my P1391 code
Hope this helps someone.

BlueRidgeMark

It's an 8 year old thread.