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1998 5.7 misfire

Re: 1998 5.7 misfire

Postby filstoy » Jan 13 2012, 8:37pm

Isn't that the CSFI engine that had the sticky poppets ? Might want to check into that.
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Re: 1998 5.7 misfire

Postby potsy [OP] » Jan 13 2012, 9:04pm

Not sure what you mean does the throttle body have the popets? Or is that the fuel injectors. I have throttle body.
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1998 5.7 misfire

Postby Bigredchev » Jan 13 2012, 9:14pm

Under the upper intake cover is the fuel injector assembly. It has a central injection module with 8 tubes running to poppet valves In The lower Intake just before the valves. The tubes with the poppers are replaceable, and notorious for failing.
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Re: 1998 5.7 misfire

Postby potsy [OP] » Jan 13 2012, 9:18pm

I will have to check into that.
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Re: 1998 5.7 misfire

Postby filstoy » Jan 13 2012, 9:35pm

My info only shows a CSFI engine on your truck. Of course I'm not saying it definitely does because my info could be wrong. Have a look at this link and see if this is your motor. It explains the problem. The system under the upper intake. Each cylinder has a poppet and they can play heck with misfires and gives that code. If that's it, you can try running some Chevron with Techron through it which sometimes works. If not it gets more involved. The dealer has a better cleaner that they shoot directly through the system. I've seen this a few times.

http://www.off-roadweb.com/tech/1012or_ ... index.html
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Re: 1998 5.7 misfire

Postby filstoy » Jan 13 2012, 9:56pm

BTW, here's a link to the actual GM service bulletin if you want to take a look at it.

http://members.shaw.ca/betterthanyoutoo ... Poppet.htm
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Re: 1998 5.7 misfire

Postby ASTE25 » Jan 14 2012, 12:10am

That would make sense, I didn't even think of the injector issue. Good call filstory!
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Re: 1998 5.7 misfire

Postby filstoy » Jan 14 2012, 5:08pm

ASTE25 wrote:That would make sense, I didn't even think of the injector issue. Good call filstory!


Thanks but don't give me too much credit. I fought with it on one of my trucks and when I read the post it sounded painfully familiar :shock:
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Re: 1998 5.7 misfire

Postby ASTE25 » Jan 14 2012, 5:50pm

Yes, but your previous misery could save poysy some grief.
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Re: 1998 5.7 misfire

Postby baghdadguy » Oct 05 2012, 10:35pm

I have a '96 with the same issue- P0307. Only #7 cyl.

Shop is telling me leakdown indicates a bad valve guide- was getting misfire only on #7. Changed plugs, wires, and distributor. Still had the 'miss'.

Says getting heads fixed will remove this- says likely that one valve is bad. When I changed plug, it didn't look bad, truck didn't have a valve noise, and other than the miss, seemed to run fine even under load/acceleration.

This a possibility? Seems odd to me.
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