Jeep Enthusiast Forums banner

Stalling then crank no start in '13 jku

6K views 18 replies 8 participants last post by  punkin 
#1 ·
For the past few months I've been experiencing a problem that gets progressively worse.
First off, it's a 2013 wrangler jku sport with manual trans, motor is stock, no killswitches, etc.
Every so often when going into 1st, engine unexpectedly stalls even when giving adequate throttle. For about 5mins after stalling, engine will crank but won't start, and occasionally sputter or cough. No CEL or any indication. After waiting 5mins, engine turns over like there was never an issue.
Additionally on the highway, engine will stall out when giving heavier throttle (I.e. throttle when bogged down in 6th gear @55mph). Since it's manual, by being in gear it restarts itself much like a pop start. Noticeable lack of power occasionally while driving, feels normal sometimes, bogged down others.
So far I looked into the known faulty fuel pump relay, tested it via bypass cable with indicator light, everything checked out, relay and fuel pump are functioning properly.
Leaning towards a vacuum or idle air control valve issue now.
Anyone experience problems with this or have any suggestions? Almost stumped here.
Thanks in advance
 
#2 ·
Stalling

A IAC operates more like a metered leak to maintain Idle. So you would end up with a start, and then stall unless you gave it a little pedal to open up the throttle body.

Have you checked actual fuel pressure while its not starting? It should be 59 psi +/- 5 psi.

Most of the other checks it has listed in the trouble shooting tree are using a scan tool to see if the modules important to engine start are awake.

If you wanted to check it for a vacuum leak, connect a vacuum gauge and at idle it should be around 20 inhg, if its waaaayy lower like around 5 inhg you have a vacuum leak. Then it can be found with a smoke machine. But, if it did have a leak it should also be running rough.

Good luck,
 
#3 ·
Ever figure it out?! Just picked up a '13 JKU automatic. Stalled twice and when I go to start it back up it continues cranking even after I let go of key, and doesn't start. Disconnecting the battery and waiting a few before reconnect solves the issue. It's going back to the dealer Monday, he suspects crank or cam shaft sensor.
 
#5 ·
Hey there, I did figure it out, sorry for not posting the reply here. In my case it was the crank shaft position sensor. I tried it on a whim, since it was only a $15 part, and I've had no problems since then. Best of luck, that problem was certainly a nightmare for me
 
#6 ·
When crank position sensors go out they can become very heat intolerant. that causes em to act just like you described - the biggest tell when it IS the crank sensor - while cranking the no start (or coasting through the dead engine) - no RPM shows on tach...
 
#9 ·
Joe56888 said:
Hey there, I did figure it out, sorry for not posting the reply here. In my case it was the crank shaft position sensor. I tried it on a whim, since it was only a $15 part, and I've had no problems since then. Best of luck, that problem was certainly a nightmare for me
Did it ever throw a code? My CEL does not come on
 
  • Like
Reactions: jay-h
#10 ·
JeepCares said:
Hi shull360CJ7, Let us know if you'd like us to follow up with the dealership once your Jeep is in for service. Kori Jeep Social Care Specialist
It's at the dealership now. Stalled on the way there. I'm told it will be there until they can duplicate the problem. No check engine light so I hope I'm not Jeepless for three weeks.Its anyone's guess when it will do it again. Frustrating because I think replacing the cam shaft sensor is the answer
 
#12 ·
It never did throw a cel for mine. In the event that the dealer can't duplicate the problem, which is often the case, I would go ahead and replace the sensor yourself, you can get them from the dealer parts Dept for about $15, and it takes less than a minute to replace.
 
#13 ·
Joe56888 said:
It never did throw a cel for mine. In the event that the dealer can't duplicate the problem, which is often the case, I would go ahead and replace the sensor yourself, you can get them from the dealer parts Dept for about $15, and it takes less than a minute to replace.
Sadly that's probably what I'll have to do. Just frustrating, I've owned the Jeep for two weeks.
 
#14 ·
Not really. You CAN look at the tach (or more preferably the RPM and CKP circuit Voltage values in an OBDII reader) next time it wont fire. If its says zero RPM while cranking - the PCM sees it as not cranking (no RPM signal equals no spark / no fuel requirement). If it DOES show (about 250-300) RPM, its probably NOT the crank position sensor (circuit). If its running and starts acting up - again look at the tach - if the tach is swinging wilder than the actual RPM - it probably IS the sensor (circuit). Problem is then that just changing the sensor may not be the fix - sure it then runs - but how long before the new sensor goes bad from intermittent shorts in the wire or whatever other REAL underlying (circuit) problem existed. When do you check the REST of the circuit? after the second sensor?

In reading the thread - one post mentions crank pos sensor (CKP) another cam pos sensor (CMP). A bad crank sensor may not throw a CEL (as the PCM is waiting signal for RPM - no problem). A bad cam sensor almost certainly will as valve and fuel delivery timing directly effects emissions. (yes a crank sensor can be intermittent failure and throw misfire as well as sensor codes - but not always!). Best way to understand is - crank sensor tells PCM when to fire spark plug and how much fuel to give, cam sensor "tunes" the package by telling the PCM WHEN to squirt the fuel.

The symptoms of a bad CAM sensor are frequent stalling, poor idling of the car at 500 to 600 rpms, a massive drop in the rpms slowing the car, a noticeable drop in engine power, poor mileage, abnormal acceleration activity, frequent stumbling, etc.,

The symptoms of a bad crank sensor are an erratic RPM value with steady actual RPM, on revving the engine, it may cause misfiring, motor vibration or backfires. Acceleration might be hesitant, and abnormal shaking during engine idle might occur. It may feel like it shuts off and back on while driving. In the worst case the car may not start. The first sign of crankshaft sensor failure, usually, is the refusal of the engine to start when hot but will start again once the engine has cooled (and when NOT STARTING WILL BE EVIDENT AS NO RPM SIGNAL WILL BE AVAILABLE FOR TACH OR PCM).

One detail of designs is the "three wire" inductive crank sensor - the wires are hot (from PCM) ground (from PCM) and signal (from excitation of magnet on sensor). That excitation CAN be effected by picking up stray electrical pulses from elsewhere in the vehicle engine bay - a three wire in a bad run (like in a hot zone with other wires or an accessory added running its wires along the sensor wires) can become intermittent problems.

Without an OBDII reader that shows live reads (and RPM display is from read of the sensor pulses per minute) you can still test - but only with a digital multimeter that measures freq (the JK is a 3 wire hall effect) Here is a good write up that could save ya some $$$...
 
#16 ·
Been at the dealer a week and hasn't done it. So, I'm picking it up either today or Monday. They believe it is a bad ground somewhere. Hopefully it doesn't do it again when I get it home. :-(
 
#17 ·
And it did it again today. Backing out of a parking spot, shut off out of the blue. Started right back up
 
#18 ·
I was having consistent hesitation when down shifting (at about 2K RPM), lack of power, and dies once in a while while driving 0.o

I replaced the Crankshaft position sensor (17$ with tax in PA). Easy swap, took 10 minutes. Now she runs better than ever. shifting is smooth and precise. So far so great!

I found the answer, here in the forums... thank god for the internet!
 
#19 ·
I was having consistent hesitation when down shifting (at about 2K RPM), lack of power, and dies once in a while while driving 0.o

I replaced the Crankshaft position sensor (17$ with tax in PA). Easy swap, took 10 minutes. Now she runs better than ever. shifting is smooth and precise. So far so great!

I found the answer, here in the forums... thank god for the internet!
I was having the same issues and replaced the CPS also and so far so good! Easy cheap fix!
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top