JohnC

2006 Jeep Grand Cherokee Randomly stalls, bucks, won't rev and PCM won't read

20 posts in this topic

My moms 2006 Jeep Grand Cherokee 4x4 finally broke down last night. The check engine light cam on and I tried to diagnose it, but PCM is coming back dead (88888) like it has just been cleared or battery has been unplugged. 

 

It'll start sometimes and run. Sometimes it'll start and run rough and quit. Other times it won't start at all unless I give it some go-pedal.

 

When I got it running once, it wouldn't take more than an 1/8 throttle and it'll buck and fall on its face while driving. It's like it's in limp mode with the rev limiter set really low because in park, I can floor it and it'll cut out pop and then do like a rev limiter set at 1,500 rpm's or so. 

 

After it quits, it sounds like something under the hood continuously makes almost an electric sound as if say, a solenoid or DBW TB is trying to open and shut repeatedly but it intermittently happens. 

 

I could have sworn I heard a static like electric noise a few times under the hood, too. Like whatever is making the noise might be shorting out.

 

Any ideas?  :meh:


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wires or Coil on Plug?

 

 

when it does start will it idle smooth or no?

 

Not sure, but being an 2006, I'd bet it is COP.

 

It's a mix of all of the above. It'll run rough sometimes. Sometimes smooth. 

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"computer comes back dead"....What's that mean/what "scanner"/any data?


 


"It'll start sometimes and run."   How does it run at that point?  (Does it EVER run "normally"?)


 


When it "pops" is it back through the intake, or out the exhaust?


 


 


A few years ago I fixed two 3.7s, both had broken valve spring/dropped valves.  BEWARE:  If it's a broken a spring but hasn't dropped the valve yet.  You'd wanna catch that problem as early as possible.   Symptoms of broken valve spring can be similar to what you describe (except the noise under the hood with engine stationary).


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"computer comes back dead"....What's that mean/what "scanner"/any data?

 

"It'll start sometimes and run."   How does it run at that point?  (Does it EVER run "normally"?)

 

When it "pops" is it back through the intake, or out the exhaust?

 

 

A few years ago I fixed two 3.7s, both had broken valve spring/dropped valves.  BEWARE:  If it's a broken a spring but hasn't dropped the valve yet.  You'd wanna catch that problem as early as possible.   Symptoms of broken valve spring can be similar to what you describe (except the noise under the hood with engine stationary).

I'll have to get video this weekend so you can see what's going on. :yes:

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"computer comes back dead"....What's that mean/what "scanner"/any data?

 

"It'll start sometimes and run."   How does it run at that point?  (Does it EVER run "normally"?)

 

When it "pops" is it back through the intake, or out the exhaust?

 

 

A few years ago I fixed two 3.7s, both had broken valve spring/dropped valves.  BEWARE:  If it's a broken a spring but hasn't dropped the valve yet.  You'd wanna catch that problem as early as possible.   Symptoms of broken valve spring can be similar to what you describe (except the noise under the hood with engine stationary).

Would a leakdown test show this??? 

 

I would check all the electrical connections under the hood just in case as well. Chrysler products have some whacked electronics...

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"comes back dead" and "no code" are two different issues.  Which is it (back to my first question)?

It won't read at all. Just shows blinking 888888's and it's supposed to show codes because the check engine (MIL) is on and chimes every so many secs.

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Is the cel on when it running or just koeo? If it's on when it's running, then there's a fault in it. You need to figure out the no communication issue first, it could be as simple as a blown fuse, but I have also been replacing a lot of PDC's in Chrysler products lately.

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I just thought about it but he may be just doing the Key On Key Off Key On Key Off Key On Code read that the ODO Displays, there could be an issue there if its displaying only 8s


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Is the cel on when it running or just koeo? If it's on when it's running, then there's a fault in it. You need to figure out the no communication issue first, it could be as simple as a blown fuse, but I have also been replacing a lot of PDC's in Chrysler products lately.

CEL is on -- key on engine running...

What is PDC?

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I just thought about it but he may be just doing the Key On Key Off Key On Key Off Key On Code read that the ODO Displays, there could be an issue there if its displaying only 8s

I tried to scan it:

Key on engine running

Key on engine off but in start

Key off engine off

All read 8's across the display. :confused:

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Not had time to deal with it yet.

I just finished a 60hr cert class and so much going on right now.

Might be the weekend, weather permitting.

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Ok, I used a newer OBD2 scanner and got some codes:

P0300

P0339

P0335

Two point to crank sensor one points to ignition fault.

I suppose since two of three point to the crank sensor, I'll change that first.

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