Misfire on every cylinder? - JeepForum.com

 
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post #1 of 2 Old 09-11-2004, 08:21 PM Thread Starter
f1rz06
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Misfire on every cylinder?

Help please....

I have a 99 Grand Cherokee V8 and it's showing misfires on all 8 cylinders, well it has a code for misfire on each of them. There is another code that is thrown which is some sort of speed sensor but the speedo functions normally. These problems both seem to have arisen around the same time.

Since they have come the car will not shift into OD 95% of the time and the shifts have become very harsh.

Now, I'm a Chevy guy myself but this seems to me like Chrysler's version of Chevy's "limp home" mode where the car will not shift into OD if it thinks it has a catalyst damaging code, which a misfire counts as.

Any thoughts?

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post #2 of 2 Old 09-12-2004, 08:28 PM
akshunj
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Posts: 30
Crankshaft Speed/Velocity Sensor

If you're misfiring on ALL cylinders I would look at the crankshaft velocity sensor. It may be called a crankshaft position sensor on a Jeep. That is the speed sensor you are refering to.

The computer detects the velocity of the crankshaft by the frequency this sensor spits out. If a cylinder misfires, the frequency decreases as that cylinder becomes a drag on the crankshaft due to the lack of force provided by the fire stroke, slowing things down.

If you were misfiring on every cylinder the Jeep would barely run and idle like complete crap. Let me know how it turns out.

Rick.



Quote:
Originally Posted by f1rz06
Help please....

I have a 99 Grand Cherokee V8 and it's showing misfires on all 8 cylinders, well it has a code for misfire on each of them. There is another code that is thrown which is some sort of speed sensor but the speedo functions normally. These problems both seem to have arisen around the same time.

Since they have come the car will not shift into OD 95% of the time and the shifts have become very harsh.

Now, I'm a Chevy guy myself but this seems to me like Chrysler's version of Chevy's "limp home" mode where the car will not shift into OD if it thinks it has a catalyst damaging code, which a misfire counts as.

Any thoughts?
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