88 chevy s10 backfires?

  • Thread starter Thread starter Robert L
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Robert L

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i have a newly built 2.5 that was board over. after one yearit sat for thewiter ran fin for 2monthsand ioccured a back fire aroud 4500 rpm. i have changed distibitor, cap, rotor, took out cat, new wires plugs. vacume lines egr valve. timed it. it can only run ok when i keep my map sensor unpluged from the computer but still connected. but i have bad gas milage when doing so. i just dont know what is wrong. my computer when all is hooked up will read nothing is wrong but it will backfire repeaditly when the throtle is not in a steady position. i have narrowed it down to my vacume lines may be ran wrong or a bad head gasket . but if it is a bad head gasket shouldnt it pop- backfire nomater what? please help me
 
Dude you need to run your spell check before you post your question. To me it doesn't sound like you have a head gasket issue, you would have a sweet smelling smoke coming out of the tail pipe sounds like a rocker arm spring may have broken or a rocker arm is to tight restricting the valve movement. if you used the original cam it could have a bad lobe or a valve is just sticking. If it ran good for 2 months i would look more to a broken rocker arm spring.
 
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