I need idea's. I am working on a 1998 GMC 3500 5.7L that is running rich on both banks. Here's what's been done so far. Cap, rotor, plugs, and wires were replaced before I got the vehicle. I rechecked the cap and rotor to make sure that signs of ignition contact were on each terminal and also checked wire routing - both are good. Verified key on and engine running Fuel Pressure. Checked for fuel pressure drop - minimal (about 10 PSI in 25 min). Performed injector balance test - normal (all at 13psi drop). I swapped out the Coil and Ignition module with a known good one - no change. Disconnected MAF - no change. Disconnected both #1 O2 sensors - no change. So I finally removed the upper intake plenum to check the fuel pressure regulator. When 20-25 of vacuum was applied no fuel came from regulator, but I can smell fuel vapors from the vacuum hose. I know that this can cause a rich condition but I haven't had vapors cause a vehicle to run this rich (-18% on both banks). Before I tell him to spend 80 bucks on gaskets and a regulator I want to make sure I check everything.
SOURCE: 1994 gmc seirra k1500 4.3 engine 4x4 hesitation
Possible erratic signal from the crank sensor
SOURCE: 97 GMC Safari w/ 4.3(W)
your injector spider it look like a spider under the planium its the injector pipe that are broken if you check everything else that it you need to remove the planium you will see that injector module be carefull loosy plastic clip holding those injector in they break easy let me no and thanks for using fixya
CHECK THE AIR INTAKE TUBE FOR TEARS OR LEAKS. A LARGE VACUUM LEAK WILL CAUSE THIS.
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