Quote:
Originally Posted by Little Red Truck Tha
CT,
Bob here (Little Red Truck). Mine is the 2wd, Chevy C3500, L80E, 7.4L, TBI that you fixed last year with the EGR switch.
Current issue is starting and low throttle miss-fire (45-50 mph). All plugs, wires, cap, rotor are new. No codes from Snap-On scanner. Scope showed good voltage thru wires. Snap-On could not find gear selected (Park) and searched P-L1 continuously. Cable that indicates gear selected in dash is broken. Contacts in P-R-N-D switch on column were cleaned an lubed with Di-electric grease. Ran compression check: 153,166,146,158,152,144,152,152 (1-8). Blocked EGR vac line and verified EGR open/close.
Nothing changes miss-fire.
Any ideas on where to go next?
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I think I actually remember you. If I remember correctly you are a can-am race car guy.
A light throttle misfire at that speed is often caused by a secondary ignition leak, but you changed out all those parts.
It could be a lean misfire caused by a vacuum leak or low fuel pressure.
A dirty fuel filter can cause low fuel pressure.
Try the easy things first because the TBI trucks have no fuel pressure test port and the pressure should be checked with the engine running.
Make sure the distributor shaft will not wiggle sideways.
Instead of tacking onto this thread, new topic threads should get started for other topics so there are no misunderstandings.