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1990 GMC V1500 Suburban 5.7L Excessive Emissions
Posted to GM Driveability on 5/16/2008 10 Replies

This vehicle will lose vacuum under load and NOX is failing. Tire size is 10 to 12" over factory spec. It is useing Thorley headers with 3" exhaust. Have tried 1.5", 2" and 2.5" restrictors in exhaust. 2" is best for loss of vacuum under load. NOX is still hig...

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Message Closed w/FIX

car Vehicle Data

1990 GMC V1500 Suburban

VIN 1GKEV16K7L
Engine5.7 L / 8 cyl / GAS
Trans4-speed Automatic
DeliveryFI / TBI
EmissionsCA.
SymptomsExcessive Emissions
OccursAlways, Under Load
Message Closed w/FIX

car Vehicle Data

1990 GMC V1500 Suburban

VIN 1GKEV16K7L
Engine5.7 L / 8 cyl / GAS
Trans4-speed Automatic
DeliveryFI / TBI
EmissionsCA.
SymptomsExcessive Emissions
OccursAlways, Under Load