89 w100 4x4 318 np435. no codes
This TBI system has been quite buggy and the PO and his backyard mechanic were hacks. When i first the truck it ran terribly. it backfire, stall when coming to a stop, running filthy rich, and the engine was missing. they swapped out 3 throttle bodies in an attempt to cure the drivablilty woes
During my typical diagnostic routine i found a disconnected power wire for the TBI temp sensor and 3 spark plugs with an almost closed gap. that cured my overly rich condition and dead cylinders.
not too long after that, the fuel pump was replaced, wiring terminals tightened up, hose split repaired.
I have 2 current issues. First, the idle is low and the IAC hunts a little until it finds a sweet spot. On a cold start, it fires right up but the idle creeps up into normal rpm (i dont have a tach but it sounds close to normal idle rpm) then it hunts a little and stabilizes. when coming to a stop the rpms will drop and the engine stalls. this isnt consistant but it happens often about 3 out 5 times. i tried to adjust the IAC rod but that doesnt help.
the second issue is the lag or hesitiation on acceleration that often results in a backfire through the throttle body. full throttle, half throttle feels the same. It feels like the igntion cuts out, backfires with one big puff, comes back and can spin some tires of i was into enough throttle.
timing is set @ 10deg, connections appear good and clean, dizzy shaft has very little play (no more than .005), however the cap is corroded and i will be replacing it today.
one thing i did notice is that my timing light does not have steady flash so i know the igntion has a miss. i can only feel this miss if im in too high of a gear with light throttle (not lugging but dang near close to it)
i currently suspect the pick-up coil, ECM, and igntion coil. is there anything else i should consider before i start throwing parts at it?
This TBI system has been quite buggy and the PO and his backyard mechanic were hacks. When i first the truck it ran terribly. it backfire, stall when coming to a stop, running filthy rich, and the engine was missing. they swapped out 3 throttle bodies in an attempt to cure the drivablilty woes
During my typical diagnostic routine i found a disconnected power wire for the TBI temp sensor and 3 spark plugs with an almost closed gap. that cured my overly rich condition and dead cylinders.
not too long after that, the fuel pump was replaced, wiring terminals tightened up, hose split repaired.
I have 2 current issues. First, the idle is low and the IAC hunts a little until it finds a sweet spot. On a cold start, it fires right up but the idle creeps up into normal rpm (i dont have a tach but it sounds close to normal idle rpm) then it hunts a little and stabilizes. when coming to a stop the rpms will drop and the engine stalls. this isnt consistant but it happens often about 3 out 5 times. i tried to adjust the IAC rod but that doesnt help.
the second issue is the lag or hesitiation on acceleration that often results in a backfire through the throttle body. full throttle, half throttle feels the same. It feels like the igntion cuts out, backfires with one big puff, comes back and can spin some tires of i was into enough throttle.
timing is set @ 10deg, connections appear good and clean, dizzy shaft has very little play (no more than .005), however the cap is corroded and i will be replacing it today.
one thing i did notice is that my timing light does not have steady flash so i know the igntion has a miss. i can only feel this miss if im in too high of a gear with light throttle (not lugging but dang near close to it)
i currently suspect the pick-up coil, ECM, and igntion coil. is there anything else i should consider before i start throwing parts at it?
