Crankshaft Position Sensor / Flywheel Mystery?? - Jeep Wrangler Forum
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Old 09-01-2019, 09:55 AM
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Crankshaft Position Sensor / Flywheel Mystery??

Hello. I have a 2001 TJ, 4.0L with automatic transmission. 125K miles.
A lot has been replaced including a rebuilt transmission at 100K miles.

The vehicle started running rough and throwing 300 codes (misfires) a couple of years ago. Also rough idle when warm and just after restart. Then about a year ago I had a walk home and traced the problem to the CPS. Replaced it and everything seemed fine. But the codes and rough idle came back.

Then another walk home. I thought it could not be the CPS again, but when I removed the sensor, it had been sheared off at the tip - physical damage. Also during this time, I would occasionally hear a loud clanging noise from under the car - it sounded like I was running over a metal plate. This noise happens intermittently, usually when slowing down - weird. But also has happened with the car in park a couple of times. Also should add, occasionally the car would stall while driving down the road - including highway, then restart.

Another walk home yesterday - the engine made the clanging sound and then went dead - removed the CPS and the tip is sheared off again. *the CPS is inserted in the side of the bell housing and senses the rotation of the flywheel to transmit the position of the cranks shaft / pistons.

Checked the flywheel and it seems ok - not warped, bolts are tight and teeth are clean.

Any ideas on what is going on here? Thank you!

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Old 09-01-2019, 10:12 AM   #2
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Old 09-01-2019, 02:32 PM
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Thank You!

I've been lurking here for years
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Old 09-01-2019, 03:13 PM   #4
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There is a paper spacer/shim that goes between the CPS and housing, did you install it?

https://www.factorychryslerparts.com...5252229AB.html
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Old 09-01-2019, 05:32 PM
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Thanks for that.



Yes sort of. I researched this a while ago. The sensor placement hole is oval so it allows for about 30mm movement in and out of the hole. I made a spacer so it would be at the furthest out possible. This didn't help. Each time the tip of the sensor is broken off, it takes about 1/4 inch of the tip.



Right now I'm thinking there is a bolt or nut behind the flywheel - on the engine side - and it is too big to pass the gap between the flywheel and the bell housing. And every now and then it hits the flywheel and flys up to hit the CPS. At least that's my working theory. Next I'm going to try to see inside there, but have not figured out how to do that because the headroom to eyeball this is pretty cramped.
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Old 09-01-2019, 05:43 PM   #6
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There are no bolts or nuts on the flywheel outside of the small bolt pattern in the center that holds the flywheel to the crankshaft.
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Old 09-03-2019, 09:09 PM
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I removed the CPS this evening. The picture here is the one I removed and a new one. Both of these are after-market. You can see that about 1/2 inch of the end of the sensor has been torn off.



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Old 09-03-2019, 09:21 PM   #8
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It's possible that your flexplate is bent or damaged. I guess it's remotely possible that you have something bouncing around in your bell housing but not likely. There's nothing natural in there that should be interfering enough to cause that kind of damage. My best guess is damaged flex plate.
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Old 09-04-2019, 08:57 AM
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Gold Miner and Jerry B. - thanks for these inputs. I am thinking flexplate (learned this is what the flywheel is in an automatic!). If it is this (which sucks), I am faced with a project (exhaust, driveshaft, transfer case, bell housing, transmission, flexplate) which I could probably do, but not efficiently - IOW it would take me 2 full days at least and probably more like a month. Or, I can pay a shop to do it - which is going to be expensive. The quest continues.
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Old 09-04-2019, 10:48 AM   #10
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Quote:
Originally Posted by Jerry Bransford View Post
There are no bolts or nuts on the flywheel outside of the small bolt pattern in the center that holds the flywheel to the crankshaft.
Factually incorrect.
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Old 09-04-2019, 09:21 PM   #11
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Quote:
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. I am thinking flexplate (learned this is what the flywheel is in an automatic!). If it is this (which sucks), I am faced with a project (exhaust, driveshaft, transfer case, bell housing, transmission, flexplate) .

No, not that complicated. I also have a 32rh and have pulled it twice this year. Remove skid and support engine. Leave exhaust connected to the engine. Remove exhaust hanger from transmission mount. Leave transfer case connected to trans and pull as a single unit. One of the top bell housing bolts is tricky to get to but not impossible by any means. The rest are easy to access. Dipstick tube bracket is connected to one of the bell housing bolts, be aware of this and drain as much trans oil as you can before separation. Pull dipstick tube. Disconnect battery and remove starter, (or position it out of the way). Disconnect and pull rear driveshaft (easy). Unplug all linkages including t-case linkage (easy). Unplug all sensors and breather tube from trans. Remove lower cover plate from bell housing. Unbolt 4 torque converter bolts, leave torque converter connected to trans. Pull back trans and inspect the flexplate. You may have to remove flexplate from engine to inspect or replace. Mark the orientation prior to removal. When reinstalling, torque all fasteners accordingly, very important.

Give yourself a full day to separate and a full day to reassemble... or two, or three depending on your tools, garage, and helper resources. You'll need a helper to help get the bell housing alignment pins 'aligned' when putting the trans back together with the engine.
You'll need a trans pan gasket and filter (easy). At least 4 qts of ATF+4.

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