2002 cmc with multiple misfire codes

2002 GMC SAVANA
150 MILES
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JDRUID
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I have a 2002 GMC savana with a brand new gmc crate motor with less than 150 miles..It is throwing a multiple misfire code on cylinders 4&7. It was giving the same exact code before we replaced the engine. We have replaced the mass air flow,crank and all the o2 sensors.we were told we may need to reflash the computer we have taken to our local gmc garage and they said they could not find anything any suggestions
Sep 13, 2011 at 2:55 PM
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ASEMASTER6371
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what about the injectors?? very important as the flow pattern may be off either giving too much or too little fuel in the cylinders.

Roy
Sep 13, 2011 at 5:46 PM
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JDRUID
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yes we have checked all the injectors and they are all fine..distributor is fine, they spent 4 hours checking everything they could and still getting the same codes. It does not throw the codes when under load but as soon as we let off the gas the service engine light comes on with the multiple misfire codes
Sep 14, 2011 at 12:39 AM
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ASEMASTER6371
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are there any exhaust leaks??

Roy
Sep 14, 2011 at 12:59 AM
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JDRUID
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No there are no exhaust leaks.
Sep 14, 2011 at 11:20 AM
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ASEMASTER6371
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sounds like you have covered all the bases with the same results. you need help of a shop with a scanner to monitor whats happening with this system. it may be a bad pcm but needs to be confirmed before this expense.

Roy
Sep 14, 2011 at 2:18 PM
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