Jeep Wrangler Forum banner

Crankshaft Position Sensor Replacement

20K views 19 replies 6 participants last post by  JemVader 
#1 ·
Howdy!
I've been having a misfire (flashing/blinking CEL) issue that's been driving me nuts!! Its been a while since I had the code read, but If I remember correctly it was throwing a P0300 (random misfire). I did some research and decided to replace the plugs and the crankshaft position sensor (CKS or CKPS?). I replaced the plugs with Champion Copper plugs gapped at whatever it says in the owner's manual. Before changing the crankshaft position sensor, I decided to start it to see if it was just the old plugs causing the misfire issue. I start it up, idles great, no flashing/blinking CEL; but the CEL did stay on (just not flashing/blinking). So i drive around town for about 20-30 min and the CEL goes off. I'm thinking WOOHOO problem solved!! Well, not so much. Fast forward a couple of weeks, and I go to start the jeep and get that dreaded flashing/blinking CEL (along with a terribly rough idle). So it looks like its time to change the crankshaft position sensor. I searched on here and on google, but couldn't find a good how-to with pictures for a 2001 TJ 4.0 manual trans. Can anyone point me to a thread or perhaps a youtube video? I found some info on a Cherokee forum saying "On all the six cylinders it should be mounted on the bellhousing at the left rear of the engine."

I'm not sure if that holds true to the TJs or not. Any help would be greatly appreciated!! :worthy:
 
See less See more
#3 ·
Thanks hosejockey! I'll give it a shot this week if the weather cooperates
 
#4 ·
Update: I replaced the crankshaft position sensor this past weekend (really easy), however, the Jeep still runs the same (misfire) and still has the blinking/flashing CEL. Arrghhhh!! I plan on keeping the Jeep forever (its paid for) so I don't mind spending money on replacing sensors that will need to be replaced eventually anyway. Would bad oxygen sensors cause a misfire condition like this? (i'm thinking NO, but I suppose anything is possible). Any ideas on what to replace next?
 
#6 ·
I didn't clear the old code. Can I do that by just unhooking 1 of the battery cables, or do I have to have an OBD II tool to clear it? And I don't know if its firing the same code or a different one; i'll have to stop by Oreilly's to have them scan it (I don't have an OBD II scan tool).

Thanks!
 
#9 ·
I installed an Echlin brank crankshaft position sensor from NAPA. From what I've read on here (and other forums), that brand is supposed to be high quality.
 
#10 ·
UPDATE: So I went ahead and also replaced the Camshaft Position Sensor with an Echlin brand unit from NAPA. Installation was a breeze, and this time I unhooked the pos & neg battery cables & left it that way for approx 12 hrs. **Helpful tidbit** I used 2 pieces of cardboard to keep the battery cables from touching the battery terminals while it was unhooked...quick, easy, cheap, and effective!

So after around 12 hrs of the battery cables being disconnected, I re-connected them & fired up the 4.0. Idle was kinda rough, but didn't seem as bad as before and it was NOT throwing a CEL! So I take it on a test drive through the neighborhood & let it get up to operating temp, then I do a few 3rd gear pulls to 4k RPM or so to see how everything is reacting. I can feel the motor kind of "missing/stuttering" in the 2,000-2,500 RPM range pretty much the whole time. Then I get my dreaded flashing/blinking CEL back, along with the rough idle at basically all RPMs. At thing point, i'm thinking I need to check the fuel pressure at the rail & also check my battery to see if its putting out enough volts. Any other ideas? Thanks in advance!!

(I may start another thread for my whole engine misfire adventure, since this has evolved from just a crankshaft sensor replacement...)
 
#13 ·
The old camshaft sensor looked toasted. All the metal contact points were black instead of silver. And no, I haven't had a chance to go have the code read yet...I need to do that!
 
#19 ·
well dang, this is starting to get expensive...but it matches up with some other info i've been reading online lately. Seems a good bit of these misfire issues are related to valves and/or springs. I watched a youtube video about to remove the head on a 4.0...looks like a good amount of work (but that guy had a cracked head). If i'm just replacing the valves & springs myself, I just need to remove the valve cover, correct? I don't have any firsthand knowledge of getting into these motors, but i'm willing to learn!
 
#20 ·
To replace valves you need to pull head. Springs I did with the head on. I pulled the valve cover and used about ten feet of nylon rope and you pull all the plugs and start from front to back get the first cylinder to top dead center on the compression stroke and then feed the rope into head and rotate till its tight in the cylinder to hold the valves in place and use your valve spring tool to swap out the springs.
 
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