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jeep cherokee 2.5l missing on number 1
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James_85_jr
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Mar 16, 2010, 2:25 PM
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jeep cherokee 2.5l missing on number 1
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I have a 93 jeep cherokee 2.5l that has a miss just above idol and sometimes when idling it is a dead miss when it does miss you can pull the number 1 plug wire off and it doesn't change the tune of the motor if you get it on a hard pull it doesn't miss as long as the rpm's are high enouf so far i have replaced the plugs wires distributor cap rotor button and coil nothing has changed the tune of it at all i checked the compression number 1 2 and 4 have around 125 psi and number 3 has 145 psi for some reason but it doesn't miss on any cylinder other than number 1
before i sink any more money in this does anyone know what could be wrong im thinking of a stuck lifter or valve because when you get the rpm's up high enouf on a good hill it has lots of power like it frees up something.
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steve01832
Veteran
Mar 16, 2010, 4:44 PM
Post #2 of 13
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Re: jeep cherokee 2.5l missing on number 1
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Have you put a noid light in the #1 injector harness to check for injector pulse? When you pull the plug wire off is there spark? If there is spark, try another spark plug, or swap with another cylinder to see if the problem moves or stays on #1 cylinder. Start here and post back with the results.
Steve
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James_85_jr
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Mar 16, 2010, 6:25 PM
Post #3 of 13
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Re: jeep cherokee 2.5l missing on number 1
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i have swapped the plugs and wires out with other cylinders and there is spark on number one but i don't have any way to test the injectors short of unpluging them and listening to the change in the motor
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Sidom
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/ Moderator
Mar 16, 2010, 7:55 PM
Post #4 of 13
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Re: jeep cherokee 2.5l missing on number 1
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In addition to the tests that Steve mentioned you could also do a running compression test if your gauge has a schrader valve in it. Normally you want to see about 1/2 the amount of the cranking compression test (which should've been done with the throttle wide open) you do have to continually "burp" the gauge. If you are seeing a 5 to 10 lb drop on the running test as compare to a good cyl, then you could very well be looking at a valve train problem..........
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James_85_jr
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Mar 18, 2010, 10:46 PM
Post #5 of 13
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Re: jeep cherokee 2.5l missing on number 1
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is there any other way to test if there is a valve train problem i don't have a compression tester that can do a running compression test?
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James_85_jr
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Mar 21, 2010, 8:24 AM
Post #6 of 13
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Re: jeep cherokee 2.5l missing on number 1
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does anyone know how to test the valve train with out doing a running compression test?
i have checked all the parts places for one of those compression tester's to do a running test and none of them have one around here. 
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Sidom
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Mar 21, 2010, 8:51 AM
Post #7 of 13
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Re: jeep cherokee 2.5l missing on number 1
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You can use a vacuum gauge to see if something is going on. If the vacuum reading is steady and @ about 18" or higher and then off idle gets shaky, that also would indicate a valvetrain problem.....
If you have a little time you can check out this video. What you should focus on is how they shimmed a rocker arm to verify the problem. I know you have the 2.5 but it's a way to definitely nail down a problem before tear down.
http://www.autonerdz.com/...ranglerfromhell.html
Just a side note. The S O Modis would capture that problem, just not at that time division that is set and the resolution wouldn't be as good but it could be found....... Not knocking the Pico, it's very nice scope but just had to add that......
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Hammer Time
Ultimate Carjunky
/ Moderator
Mar 21, 2010, 3:50 PM
Post #8 of 13
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Re: jeep cherokee 2.5l missing on number 1
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You can do a running compression test with a regular compression tester. Just remove the schraeder valve first.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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James_85_jr
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Mar 24, 2010, 5:09 PM
Post #9 of 13
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Re: jeep cherokee 2.5l missing on number 1
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I went ahead and pulled the lifters on the number one cylinder and the exhaust lifter looked like something has hammered it like a ball ping hammer what can cause this? that way i can figure out what to do to stop this again.
ps. i changed that lifter with a new one and the jeep runs great thanks for the video
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James_85_jr
User
Mar 25, 2010, 10:47 AM
Post #11 of 13
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Re: jeep cherokee 2.5l missing on number 1
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never herd of a lifter sticking that bad the hammered side was on the cam and when i set beside the other lifter it was just over 1/8" shorter from the hammering
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Sidom
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Mar 25, 2010, 4:38 PM
Post #12 of 13
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Re: jeep cherokee 2.5l missing on number 1
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Yea, you get too much lash and it's surprising what can happen. Hopefully the lobe on the cam didn't get damaged. Was it on the intake or exhaust side?
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James_85_jr
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Mar 26, 2010, 9:16 AM
Post #13 of 13
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Re: jeep cherokee 2.5l missing on number 1
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it was the exhaust side
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