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Unread 09-14-2009, 08:51 PM   #1
junkur
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Join Date: Mar 2006
Posts: 50
258 sputters revved.

ok, this one is a little long and complicated.

a couple months ago, the old engine in my cj7 started sputtering all of a sudden while playing in the mud. but it cleared up and ran fine until it got swapped out for another 258. (it had cracked rings).


now about a month ago, the new 258 in my cj7 started sputtering all of a sudden, just like the old one. there is a loss in power, but not much. it still holds 5th gear just fine on the road(4.56 gears with 32" tires). it will sputter between about 1000-1800 rpm. anything higher and it runs smooth. also, if i run the rpm's up very slowly, it's fine too. it doesnt need to be under load either, it will do it just sitting in neutral.

now it does have a 4wd HEI in it, and yes, i know the issues with it. it ran great in the old engine. i swapped in an engine out of an '81 AMC Eagle. a week after the new engine was in, it started doing it and hasnt stopped completly since.

the jeep has an MC2100 carb on it. when it started sputtering, i took the top off the carb, and sprayed out the inside with gumout. it cleared up for a couple minutes. the next day, i added some stp gas treatment to it and ran fine all day.

this one has me stumped. i think its the carb, but it was just rebuilt a month before the new engine went in.

i know the issues with the HEI, but it will run just fine sometimes, and others, it doesnt.

any input would be appreciatted.
sorry for the long, complicated post

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Unread 09-14-2009, 09:01 PM   #2
scottymac62
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1977 CJ5 
 
Join Date: May 2008
Location: Locust Grove, GA
Posts: 1,464
Check to make sure your engine block is grounded well.
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'77 CJ-5 Renegade 304 / T-150, Dana 20, 30/20 axles, Aussie Locker in the Dana 30, American Racing 15x10 Outlaw II's, 33" Dynapro M/T's" ,Optima Battery, TeamRushed + Summit Racing CDI ignition, FlowKooler water pump, Edelbrock Performer Intake Manifold, Holley 4160 390cfm, Herculiner, Silver Ceramic Coated Hedman Hedders, Flowmaster 40's.
Warn PowerPlant HD 12K Winch, Dirtworx front and rear bumpers.
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