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frostbiker

2000 Grand Cherokee Rough Idle Issues

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Just found out it is bad gas. Possible sugar or something else in the tank. I'm not happy.

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Where to start?

 

Traced fuel problems from the pump, filter, lines, rail, injectors, plugs and coil packs. All that is fine. Replaced plugs, purged the lines, cleaned injectors and did continuity tests on injectors and coil packs. All of that is fine. I started the truck up on Thursday. Was still rough, but much better. No codes. Shut it off and went to do something else. Came back and tried to test drive. Idled like the very first day. Code P0202 showed up. So, something is wrong with the number 2 injector.

 

Something dad and I should have done a while back was a compression test. Didn't think much of it at the time because we thought we were dealing with issues up to and including the injectors. Nothing inside the block. We tested compression on the #2 first. Flat expletive zero. No psi at all. Not even a blip when I cranked it over. Checked three other holes. All but the number one were in the 120 psi range. Number 1 showed 150.

 

Double checked continuity on the coil pack, pulled the rail and double checked the injector, checked the spark plug. All fine. Worst case, a blown head gasket. I'm not even gonna attempt to rebuild the engine on that one. My neighbor, the shade tree genius (no, don't laugh, he really is!), has theorized that if it is not a stuck valve, blown gasket, or other headache inducing problem, the simplest answer would be a bad rocker arm, or busted spring.

 

My work schedule returns to normal this week. I'll have a couple hours every day to break the engine down. I'm gonna get down and pull the valve cover off that side and see if there is something obvious in need of repair.

 

Wish me luck, as this is turning into a greek tragedy.

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Just thought of something.

 

Idle was rough but better when I drained the oil when I started repairs. Gets worse when oil is added back in. Sounds better after the truck has been sitting a couple weeks and started back up, gets worse when oil pulled up into the engine. Throws code P0202 this time around.

 

Somehow believe there is a fuel/air/oil mixture issue at #2 that is the ultimate problem.

 

Thoughts?

 

Also, let me ask the braintrust this: Truck is running like a top (albeit a 195K odometer top) the day this occurs. Sits in a parking lot for a couple hours. Start up at the end of the day and BLAMMO! instant issues. Would a bad head gasket present in that manner, or would it be something else?

 

Going back to my primary cause for concern (bad fuel), I don't think that was the primary issue overall. It started the ball rolling on repairs, but I think it was analogous to the root problem. I did find some foreign material in approximately 1/3 pt. of gas pulled from my tank. For all intents and purposes, the rest of the fuel was clean as a whistle when we drained the tank. The original pump and filter didn't have gunk in them, but they were old as dirt. Whatever was put in my tank didn't get all the way to the bottom to be pulled into the engine. Whatever I siphoned out was trapped at the fill neck and no further.

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Head gaskets don't just go bad there has to another issue. If you had a bad head gasket you would have coolant in the oil, oil in the coolant or combustion gases in the coolant. If you have 0 psi on cylinder 2 and already have valve cover off you need to check rocker arms, lifter, push tubes, valve tips, springs etc. If you have not removed valve cover I would suggest doing a cylinder leak down test where you pressurize the cylinder and find out where the air is going. Combustion could be bypassing the piston rings, exhaust valves or intake valves

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Head gaskets don't just go bad there has to another issue. If you had a bad head gasket you would have coolant in the oil, oil in the coolant or combustion gases in the coolant. If you have 0 psi on cylinder 2 and already have valve cover off you need to check rocker arms, lifter, push tubes, valve tips, springs etc. If you have not removed valve cover I would suggest doing a cylinder leak down test where you pressurize the cylinder and find out where the air is going. Combustion could be bypassing the piston rings, exhaust valves or intake valves
Good advice… ;)

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Finally had some decent weather and a day off to tackle the Jeep. Pulled back the valve cover over the #2 cylinder. Sure enough, I'm missing a rocker arm. Funniest thing. Now, I have to figure out how to purge the a/c lines, remove them, loosen the serpentine belt, and (fingers crossed) remove the pieces of the busted rocker arm before replacing it.

 

I do hope that is the end of the road for this.

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Good luck man. Hope it all works out.

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Can anyone tell me the best way to go about fully removing the passenger side valve cover? I was able to pull it up to view the missing rocker arm the other day, but a bad weather forecast forced me to button everything up and wait.

 

Do I have to disconnect the a/c lines running next to the cover? How do I go about safely doing that without freon blowing up in my face?

 

QUestions, comments, snide remarks?

 

Any help appreciated.

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This job sucks but you can unbolt the compressor and move the lines as needed without emptying the refrigerant. I used some bungee cords to hold everything out of the way.

 

DSCN9912.JPG

 

DSCN9914.JPG

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