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73-87 Chevy _ GMC Trucks => Performance => Topic started by: bauerranch454 on May 15, 2017, 08:43:51 pm
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Does anyone out there have any experience with the Edelbrock MPFI kits that they used to sell?? I just installed one I got off of Ebay in an 87 chevy with a TBI 454. I am having some drivability problems. It runs rich, It doesn't like to idle and I think it has less power than the original TBI. I have a couple more things to try before I run out of ideas but I was wondering if anyone knew of a good source of troubleshooting data for one of these systems? I am pretty sure the system I have is a 3562. I am a decent hand at problem solving if I can find good tech data.
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Edelbrock 3562 installation instructions (http://www.jegs.com/installationinstructions/300/350/350-3562.pdf)
With the exception of fuel pressure (typically ~42 PSI, depending on altitude and engine vacuum), diagnose MPFI using the same criteria as factory TBI. Did you replace the PROM and place the EST in bypass mode before setting the timing? The PROM is tailored to the drivetrain, so if the original application was very different from yours, drivability issues may result. In addition, Edelbrock's PROM programming concerning those kits was not very sophisticated, rather just enough to pass emissions requirements. Once you have the basics of the system functioning, a custom tune will provide surprising torque and mileage improvement. Have you connected a scanner to it?
1987 Fuel, Drivability and Emissions Manual (http://www.73-87chevytrucks.com/techinfo/7387CKMans//Fuel_Emissions/X8736_1987_GMC_Light_Duty_Truck_Fuel_and_Emissions_Including_Driveability.pdf)
Pay particular attention to anything that will impact manifold vacuum signal to the MAP sensor and FPR, such as vacuum leaks, EGR not closing due to carbon accumulation around pintle or EGR receiving errant vacuum signal from EGR solenoid. Check fuel pressure and verify that the timing is properly set. For anything more involved, you should use a good scanner.