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Should I replace my CPS for the heck of it?

Old 01-12-2016, 12:20 PM
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Default Should I replace my CPS for the heck of it?

2000XJ. 147000 miles, daily driver, Had issues recently.

1) A week ago, I drove home from work...25 miles or so, and stopped to run an errand a minute from my house. When I went back tot he JEEP it cranked but no start. Tried several times without success I lifted the hood, then tried to start, and it started strong!

2) On the way to work this morning, the JEEP ran good for about 15 miles, then stalled. Could not restart for about 2-3 minutes. Since its cold out, I'm thinking that's when the engine compartment is getting toasty warm. After waiting my 2-3 minutes, engine started good and ran another 10 miles fine.

Does the CPS have a typical life expectancy? Do I just replace it? I have no CEL, no codes, and I hate just throwing money at a potential problem.

Thoughts???
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Old 01-12-2016, 12:57 PM
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When you say no codes have you actually scanned it? or the CEL just isn't on? because codes can be pending without illuminating the light. And see if you can scan it when the symptoms occur to see if anything pops up as pending.

Does your intake manifold have the heat shield on it to prevent injector heat soak? It will look like this:

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Old 01-12-2016, 01:00 PM
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I do not have the heat shield...I was thinking that the 11 degree fahrenheit was keeping the engine a little cooler, but maybe not.

I have not checked my codes today...need to get home from work first.
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Old 01-12-2016, 01:08 PM
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The outside temp does help, but the intake/fuel rail sitting directly above the exhaust bakes it. Especially in the middle where the heat shield would go, the intake has a big opening there that lets the #3 and #4 injectors heat up.

Does your 2000 have Cali emissions? If so it will have 2 pre-cats below the intake and 4 oxygen sensor. That REALLY bakes the intake/fuel rail. This usually doesn't set a code, but does show up after the engine gets toasty. Hot fuel can also cause vapor lock which makes it really hard to start (cranks and cranks but no start).

The heat shield is only $2.28 + shipping, so $9 or so. Even if that's not your problem it's always good to have. http://www.tascaparts.com/oe-mopar/cbxcb060

A bad CPS will cause similar symptoms to yours, so you aren't wrong but it would suck to buy a new one for no reason. 150k would be about the lifespan of one, but its a pain in the ***** to replace because of where it's located.

If heat really is the problem it could also be: weak coil pack, coolant temp sensor going bad, cam position sensor, etc. Usually misfire codes would accompany those though, in addition to hard starting.
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Old 01-12-2016, 02:36 PM
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Thanks for the thoughts. I've not had this issue before, and I've owned this rig for about 10 years.

Other possible issue I am thinking is the fuel line. Its pretty rusty, and I wonder if small bits of moisture leak into the fuel line then freeze.

I think replacing the fuel line is a lot more difficult that the CPS...but I've never done either... Ha Ha.
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Old 01-12-2016, 05:36 PM
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Oh yeah...no Cali emissions on this one.


There is a code. No CEL, but P138. O2 Oxygen sensor high voltage. It is original O2 sensor. Is it related to the stalling?? Is it possible high voltage is too rich?? Maybe throttle body getting gummed up or not opening?


Really not sure where to begin. At 150K miles, maybe its not bad to throw money at a new set of O2 sensors. Just would like some opinions on what the expected life of some of this stuff is.


Thanks for any thoughts folks might have.
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Old 01-12-2016, 07:52 PM
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Yours is way different than mine. Both my 90's since 02 and my 90 since last year, do a rare no start. What "solves" it is just unplugging the CPS connector, then putting it back. (we renix can test them easy, and mine test's OK)

Details aside, that's something you can try with a "no start". I'd suggest if that makes it start, change the CPS.
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Old 01-13-2016, 10:14 AM
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OK...well...at least for now, mine seems to just fix itself. But, long term, I'm not usually too happy with problems that fix themselves. (Seems they always come back!)

Maybe I just asked the wrong questions...Maybe my question should be: What is the expected life of a CPS?? Why do they fail, anyways?? I hear tons of people say "buy a dealer replacement!' And that's fine with me, but I just don't want to replace stuff that ain't broke!
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Old 01-13-2016, 10:34 AM
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I keep spare OEM ones with me at all times just in case.
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Old 01-13-2016, 05:05 PM
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I carry a spare also. (mine will go out on a Friday while I'm out of town)
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Old 01-15-2016, 01:40 PM
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Ill second the camshaft position sensor. It's under the distributor, really easy to replace, cheap, and caused similar problems with me and didn't throw a code.
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