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Unread 12-25-2010, 10:00 PM   #1
Kevin108
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How to reindex the camshaft position sensor

From what I've read, the timing chain stretches out as you rack up the miles on your Cherokee with a coil rail and at some point it gets outside of the range the computer can correct for it. Mine got there right after I installed a new crank position sensor and hit 130,000 miles.

The process is easy. You need a helper, a toothpick or small drill bit, some basic hand tools and a "mirror on a stick" so you can see the timing marks on the bottom of the cover.

Remove the coil rail, the first spark plug and the camshaft position sensor.
Carefully place a finger of the spark plug hole.
Have your helper bump the starter a little at a time until you feel pressure.
Break out your mirror and check your timing marks.
Use a ratchet or wrench, 19mm I think, to turn the crank forwards to the zero mark.
Remove the camshaft position sensor from the camshaft synchronizer.
Loosen the retaining fork that holds in the camshaft synchronizer.
Find the small hole in the outside of the housing for the oil pump drive shaft.
Find the small hole on the magnet inside that indicates camshaft position.
Carefully turn the housing on the camshaft synchronizer until you can align those two holes and insert a toothpick or drill bit straight through them.
Tighten down the retaining fork, reinstall the camshaft position sensor, spark plug and coil rail.
Enjoy quicker starts and having avoided the problems that this stupid sensor causes when it gets even further out of spec.

The NAXJA guys finally found my problem and provided me this link to learn what the fix was. The process for finding top dead center and zeroing the timing came from my dad although I performed the work myself. It's basically the modern iteration of setting the timing on something you're led to believe you don't have to set the timing on.

Also, this is just the shade tree mechanic version of the fix. Alternately you can take it to a shop with a DRB scan tool and they can reprogram the computer to compensate the difference without ever having to open the hood or turn a wrench. A JF member in a thread I don't recall posted that the shop he went to wanted over $100 to do this. A guy in my Jeep club said he'd do it for free for me. Like anything else, YMMV.

(This may still be edited for terminology and additional accuracy.)

To illustrate the location


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Unread 12-26-2010, 08:16 AM   #2
mcthnif
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Great post. I have done this before, but You have done a great job laying out the procedure. It should be made a sticky.
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Unread 01-22-2011, 02:30 PM   #3
sbxj
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are you kidding?
I think i'd rather pay a professional to do it right than lowball it.
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Unread 01-22-2011, 10:23 PM   #4
Kevin108
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The DRB will reprogram your computer to compensate for the stretched timing chain without actually fixing the condition causing the problem. The instructions about allow you to physically adjust the CPS for the condition. The DRB might be good for fine tuning but short of replacing a timing chain simply because it stretched some, this is indeed a proper repair. Also I am not 100% certain, but I believe if you perform a factory reset on the computer, you will loose any aftermarket DRB reprogramming.

How do you think a "professional repair" would be different?
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Unread 01-29-2011, 10:13 PM   #5
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I agree... STICKY! It might be a good idea to list the symptoms you had before you made the fix.
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Unread 01-30-2011, 08:17 AM   #6
Kevin108
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When I get a chance I would like to add the codes and symptoms I was having along with more pics and the verified socket sizes for everything.
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Unread 01-30-2011, 09:41 AM   #7
ChEaPsK87
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Quote:
Originally Posted by sbxj View Post
are you kidding?
I think i'd rather pay a professional to do it right than lowball it.
what did he not do that a pro would? nothing but save $ so hate somewhere else please...thank you

great write up! i agree with everyone STICKY
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Unread 01-30-2011, 11:22 AM   #8
Paraleyes
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Nah, I do think this is an important bit of information. I see countless threads of 00-01 XJs having these symptoms. I'm sure there are many other Wranglers having this same problem too. I'll be sure to post back after I do it and let you know my results.
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Unread 01-30-2011, 12:19 PM   #9
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Quote:
Originally Posted by sbxj View Post
are you kidding?
I think i'd rather pay a professional to do it right than lowball it.
Go pay then, don't want you to get your pretty little nails dirty now. Maybe your missing the point of a "technical forum" about jeeps. Hint: It's so people can share there problems and find solutions so they don't have to pay someone $100 to fix something they can fix for FREE themselves, get it now? Geez if you don't like it SO WHAT it works and lots of people have done it, including myself, so well.... that's about all I have to say about that.
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Unread 01-30-2011, 05:49 PM   #10
Paraleyes
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Where in the world are the timing marks? Found the tab under the cover, but nothing on the balancer? Where?
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Unread 01-30-2011, 06:01 PM   #11
robsjeepxj
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Quote:
Originally Posted by Paraleyes View Post
Where in the world are the timing marks? Found the tab under the cover, but nothing on the balancer? Where?
There should be a small tab on the drivers side of the timing cover with numbers/grooves on it, the balancer just has a line on it to match them up with.
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Unread 01-30-2011, 08:18 PM   #12
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If it was daylight, you probably could have seen the timing marks in the mirror in this pic. Mine are a little greasy. Yours probably are as well. This is the area you need to look for them in.

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Unread 01-30-2011, 11:49 PM   #13
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Uggh... see my problem is I'm in a wheelchair. I can do just about anything I can reach underneath or outside the rig, but not that. I think my helper may have been looking for it at the back of the pulley. I couldn't see it at all. Looks like the balancer is actually right there with the mirror resting on it.
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Unread 01-31-2011, 12:07 AM   #14
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Thanks for posting this. I get the feeling it wont be long until I'm adjusting both mine and Paraleyes' cam sensors.
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Unread 01-31-2011, 12:33 AM   #15
ratmonkey
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NEVER turn a motor backwards. Especially when you're trying to adjust for timing chain slack.



The dealer doesn't program your computer for the fuel synch, they use the tool to monitor the dwell while turning the oil pump drive/cam sensor assembly into the correct window.


The cam sensor has nothing at all to do with what is traditionally called timing, which is spark advance. Spark advance is read from the crank sensor only.

Anyway, if you have chain stretch the proper solution is to spend 75$ on the chain and gasket set and fix it properly.
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