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popping(Backfire?) only at start up WTF?

dmc80

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99 4.0 ohv just replaced upper intake manifold gaskets, maf, iac, wires, coolant temp sens, and now i'm am getting a popping noise only in the first ten seconds after start up. Otherwise runs great. no cel. Stupid question but do motorcraft plugs go bad in under a year with only occasional driving?
 



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desertbum8

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99 4.0 ohv just replaced upper intake manifold gaskets, maf, iac, wires, coolant temp sens, and now i'm am getting a popping noise only in the first ten seconds after start up. Otherwise runs great. no cel. Stupid question but do motorcraft plugs go bad in under a year with only occasional driving?

IMO motorcraft is pretty cheap. I don't know about them going bad in a year but I wouldn't trust 'em. The popping noise *could* be a slight vaccuum leak.
 






desertbum8

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99 4.0 ohv just replaced upper intake manifold gaskets, maf, iac, wires, coolant temp sens, and now i'm am getting a popping noise only in the first ten seconds after start up. Otherwise runs great. no cel. Stupid question but do motorcraft plugs go bad in under a year with only occasional driving?

IMO motorcraft is pretty cheap. I don't know about them going bad in a year but I wouldn't trust 'em. The popping noise *could* be a slight vaccuum leak.
 






blkhwkns

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99 4.0 ohv just replaced upper intake manifold gaskets, maf, iac, wires, coolant temp sens, and now i'm am getting a popping noise only in the first ten seconds after start up. Otherwise runs great. no cel. Stupid question but do motorcraft plugs go bad in under a year with only occasional driving?

Any idea where the noise is comeing from? Is the poping out of the exaust or under the hood... the poping noise you are hearing, can only be a few things, the only way a car can backfire is when an intake valve is open as the plug is fired resulting in combustion gases being ignited while the cylendar is on the intake stroke. basicaly out of time... unless the noise you are hearing is an EGR leak the EGR should be closed on enitial start up and open when controlled to do so by the PCM, if the gasket was not seated the poping could be from the closed valve leaking exaust gases out of the gasket on start up.

as far as the plugs, no however that Q: is wide open because for example if cylender # 4 was to misfire due to any condition, it could very well fowl a plug with very few miles. Have you checked the condition of the plugs?
 






dmc80

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Last night it got progressively worse as i drove, sputtering and such. the only difference before and after the intake gasket job was the wires(autozone), I will change the plugs hopefully today and update.
 






Elessar65

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I don't mean to be insulting, but is everything put back together correctly? I know I've done some pretty retarded things before. Like mixing up the plug wires, not good btw, lol. I label them now that I have learned my lesson.
 






dmc80

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No worries, retarded is sometimes my middle name. Got the plugs pulled and they were all gapped wrong (not by me), spec calls for .052-.056, they were all around .o43. Started without out backfire but couldnt run it cuz my son is napping. Will rip it around town tonight.
 






dmc80

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Forgot to mention, replaced motorcraft with autolite xp's instead of regapping.
 






dmc80

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Filled the tank and then went light to light and a small jaunt on the highway and all is well. Just wondering if the upper manifold gasket issue was masking the plugs being bad. Never had backfire until upper man. was done a week ago...Actually dont care now that the old girl tip top again. thanks to all who gave help opinions or otherwise.
 






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