99 5.7 vortec
10

Asked by 78cameroalcohal Sep 28, 2017 at 12:55 PM about the 1999 GMC Sierra 2500 3 Dr SLE Extended Cab SB

Question type: Maintenance & Repair

I have a 99 gmc c2500 with a 5.7 vortec. I pulled
the motor and dropped 4000$ into parts. Corvette
crank cam pistons and heads. Got it running great
till last week when I cold start and try and take off
it starts to sputter real bad for a couple seconds
then launchs, the second issue when I'm giving it
gas and let off at my cruising speed it pops and
back fires every time I left off the gas. Any ideas
what it could be? My MAS just went out  ordered a
new one. Do you think this is related to my MAS?

3 Answers
10

78cameroalcohal answered 6 years ago

The mas will be here tomorrow and yes I was planning on clearing before I put the new one on. I had my buddy erase the ECU and completely rewrite everything to this new motor from the old ecu to the new it's night and day between the two. But after going threw everything the mas is the only part faulting and not sure if it could cause an issue like this

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10

78cameroalcohal answered 6 years ago

Shoot if this mas only fix s the sputter I'm happy with that hopefully it will fix the back for too if not I'll have to go threw it again and see if I can figure out what s going on causing the back fire. I will keep you posted tonight and let u know what happens with the new mas

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10

78cameroalcohal answered 6 years ago

Put the new mas on cleared n reset ecu, it's still doing the same thing but not all the time only half the time is doing the popping and sputtering

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