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03-22-2018, 07:14 PM
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#1 |
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Registered User
Join Date: Mar 2018
Location: Shelbyville Indiana
Posts: 5
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4.3 to 5.7 swapp
I have a 92 sierra 4.3 and dropped a 94 chevy 5.7. Left all the harness for the 4.3 but it runs very rough and won't even idle...any suggestions?
Should I put a carburator? |
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03-22-2018, 09:31 PM
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#2 |
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Senior Member
Join Date: May 2004
Location: Binghamton, NY
Posts: 3,453
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Re: 4.3 to 5.7 swapp
Put the 350 ECM in?
__________________
2000 GMC CCSB 454/4L80 6” lift SAS 1999 Chevy CCSB 454/NV4500 6” lift 1999 GMC Yukon 350/4L60 4" SAS |
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03-23-2018, 08:54 AM
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#3 |
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Registered User
Join Date: Mar 2018
Location: Shelbyville Indiana
Posts: 5
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Re: 4.3 to 5.7 swapp
My mechanic said the 350 rpm won't plug in he said it is different
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03-23-2018, 09:33 AM
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#4 |
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State of Confusion!
  
Join Date: Jul 2002
Location: Gulfport, MS USA
Posts: 46,586
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Re: 4.3 to 5.7 swapp
Since you were told the ECM won't interchange, maybe you can get a new program chip for your current ECM.
__________________
Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God! |
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03-23-2018, 10:23 AM
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#5 |
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Registered User
Join Date: Mar 2018
Location: Shelbyville Indiana
Posts: 5
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Re: 4.3 to 5.7 swapp
I really appreciate all of the valuuable info. Now the question is how do I get a new program chip?
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03-23-2018, 03:18 PM
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#6 |
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State of Confusion!
Join Date: Jul 2002
Location: Gulfport, MS USA
Posts: 46,586
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Re: 4.3 to 5.7 swapp
I am told you can order them thru AutoZone or other parts place. But normally they need the serial number so it can be programmed for the exact vehicle. Hopefully some one will speak up, there is someone that a few folks used to have their ecu reprogrammed, but I can't find the info right now.
__________________
Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God! |
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03-29-2018, 06:20 AM
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#7 |
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Registered User
Join Date: May 2000
Location: Alexandria, LA 71301
Posts: 1,450
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Re: 4.3 to 5.7 swapp
i did the 4.3 to 5.7 swap 6 years ago, all you need is the 350 chip for the operating parameters. you could swap the whole computer but not necessary. anybody tell you otherwise is stringing you along.
__________________
-02 avalanche (daily driver) -66 gto ragtop 389/400 (garage queen, hand-me-down from dad) -72 Tribute Trans Am (6.0LS/T56 6-speed) in progress -2003 YUKON (Wife's) -71 gmc swb fleet (current project, gonna shave everything, bags, stuff w/ 20's, gen III powertrain) -48 3100 SWB - 12/31/23 LONG TERM Project |
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03-29-2018, 09:43 AM
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#8 |
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Registered User
Join Date: Mar 2018
Location: Shelbyville Indiana
Posts: 5
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Re: 4.3 to 5.7 swapp
Thanks, I have swapped the chip only and it did not run very welll...i swapped the whole computer and it does at least run down the road
Still sputter but stays running. After a little while of running I did notice it runs ok with a miss when I first start it but then wants to stall out when I give it gas. I must have a different problem other than just the computer .. |
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03-29-2018, 11:19 PM
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#9 |
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Registered User
Join Date: Nov 2017
Location: Riverside, Utah
Posts: 28
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Re: 4.3 to 5.7 swapp
Did the timing get set correctly with the connector disconnected?
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04-04-2018, 09:54 AM
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#10 |
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Registered User
Join Date: May 2000
Location: Alexandria, LA 71301
Posts: 1,450
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Re: 4.3 to 5.7 swapp
sounds like the original ECM was bad.
__________________
-02 avalanche (daily driver) -66 gto ragtop 389/400 (garage queen, hand-me-down from dad) -72 Tribute Trans Am (6.0LS/T56 6-speed) in progress -2003 YUKON (Wife's) -71 gmc swb fleet (current project, gonna shave everything, bags, stuff w/ 20's, gen III powertrain) -48 3100 SWB - 12/31/23 LONG TERM Project |
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04-04-2018, 11:51 AM
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#11 |
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Registered User
Join Date: Mar 2018
Location: Shelbyville Indiana
Posts: 5
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Re: 4.3 to 5.7 swapp
Looks like the timing was off just a bit. Also, when I disconnected the egr hose from the sensor above the valve cover it ran so much better....
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