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Old 03-18-2013, 07:02 PM
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Multiple cylinder misfire, HELP Please!

I have a 2001 jeep Grand cherokee 4.7l v8. There is a multiple cylinder misfire and i cant get it to stay running. the day before this happened it ran just fine. one day later and my jeep shuts off going down the road at 30 mph. i try to start back up and it sounds like a whole bunch of misfires.

I have taken off the valve covers and found 3 feelers or (rocker arms) laying on top of the cylinder head. i placed them all back on properly and put it back together and still same problem, no change at all.

I just swapped out all of the spark plugs, thinking it may be something stupid, but still no change.

I need Help. Got any ideas??
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Old 03-18-2013, 07:26 PM
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Re: Multiple cylinder misfire, HELP Please!

Are ther any codes when you do the key dance?(turn to on posistion 3 times but don't crank)
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Old 03-18-2013, 09:51 PM
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Re: Multiple cylinder misfire, HELP Please!

Quote:
Originally Posted by Sawyer26 View Post
I have a 2001 jeep Grand cherokee 4.7l v8. There is a multiple cylinder misfire and i cant get it to stay running. the day before this happened it ran just fine. one day later and my jeep shuts off going down the road at 30 mph. i try to start back up and it sounds like a whole bunch of misfires.

I have taken off the valve covers and found 3 feelers or (rocker arms) laying on top of the cylinder head. i placed them all back on properly and put it back together and still same problem, no change at all.

I just swapped out all of the spark plugs, thinking it may be something stupid, but still no change.

I need Help. Got any ideas??
Welcome to the garage.
The fact that the rocker arms fell off is a sign that something is going on. Did the engine overheat lately? For the rocker arms to fall off, or the lash adjusters are bad, or the valve seats have dropped. Could you just put the rocker arms back in place, or did you needed a tool? Low oil pressure or no oil going to the cylinder head could cause the lash adjusters to get without oil and collaps, causing the rocker arms to fall off.
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Old 03-18-2013, 11:02 PM
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Quote:
Originally Posted by Frango100 View Post

Welcome to the garage.
The fact that the rocker arms fell off is a sign that something is going on. Did the engine overheat lately? For the rocker arms to fall off, or the lash adjusters are bad, or the valve seats have dropped. Could you just put the rocker arms back in place, or did you needed a tool? Low oil pressure or no oil going to the cylinder head could cause the lash adjusters to get without oil and collaps, causing the rocker arms to fall off.
The engine hasn't been overheating at all and the oil pressure has been reading normal. I could put cylinder 2 and 7's rocker arms with just a small pry bar. I'm thinking that the rocker arms are definitely a symptom, not the cause.

Could the cam sensor going bad cause this to happen? Or maybe a vacuum line or ground?
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Old 03-19-2013, 05:38 AM
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Perform a compression test,leak down test. More then likely if valves dropped they smacked the piston face possibly causing damage.
Timing could of skipped also
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Old 03-19-2013, 07:03 AM
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Re: Multiple cylinder misfire, HELP Please!

Quote:
Originally Posted by Sawyer26 View Post
The engine hasn't been overheating at all and the oil pressure has been reading normal. I could put cylinder 2 and 7's rocker arms with just a small pry bar. I'm thinking that the rocker arms are definitely a symptom, not the cause.

Could the cam sensor going bad cause this to happen? Or maybe a vacuum line or ground?
The fact that the oil pressure reads normal doesn´t say that there was (enough) oil pressure at the heads. You say cylinder 2 and 7, so rocker arms fell of on both heads? Did you check the hydraulic lash adjusters if they where feeling spongy or firm? The lash adjusters can go bad, but i wouldn´t expect them to go bad at the same time. I red of horror stories of a valve seat coming of in one cylinder and destroying several other cylinders. So first thing to do is a compression check, to see if there is anything abnormal.
A bad cam sensor could prevent the engine from starting, but yours is running. There must be something mechanical wrong inside the engine.
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Old 03-20-2013, 12:54 PM
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Loss of oil pressure at idle, oil pressure goes back up when I put on the throttle.
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Old 03-20-2013, 03:32 PM
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Quote:
Originally Posted by Frango100 View Post

The fact that the oil pressure reads normal doesn´t say that there was (enough) oil pressure at the heads. You say cylinder 2 and 7, so rocker arms fell of on both heads? Did you check the hydraulic lash adjusters if they where feeling spongy or firm? The lash adjusters can go bad, but i wouldn´t expect them to go bad at the same time. I red of horror stories of a valve seat coming of in one cylinder and destroying several other cylinders. So first thing to do is a compression check, to see if there is anything abnormal.
A bad cam sensor could prevent the engine from starting, but yours is running. There must be something mechanical wrong inside the engine.
What would happen if the capacitors were bad? I know the cam sensor is good, I have spark, compression, and fuel. Only cylinders 5,6,7 are working now. I have fuel pressure. I did a compression test and both seemed to be okay.
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Old 03-20-2013, 08:30 PM
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What psi you have on all 8 cylinders

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Old 03-20-2013, 10:13 PM
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Re: Multiple cylinder misfire, HELP Please!

Did you measure the oil pressure with an external gauge, or did you see it on the instrument panel? When really low, you probably have to check the oil pick-up screen first to see if its not (partly) blocked. When you removed the valve covers, did it look all clean under there, or was there buildup of sludge?
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Old 03-21-2013, 07:33 AM
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I have 150 psi. And I think the oil pressure was just low because of the low idle, as soon as I raise rpms it goes rght back up.
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Old 03-21-2013, 02:51 PM
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Re: Multiple cylinder misfire, HELP Please!

Was the idle that low that the oil pressure should be low as well? Normal idle is at 650 rpm. On which cylinders did the 3 rocker arms fall of and was it on both banks?
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