bigdadhack
Registered Member
Hello, I'm new to forum, looking for some help.
This is a COLD engine OPEN loop problem only, all good when warm.
I have a 91 Suburban V2500 5.7L 4L80E
Basically when the engine is cold I have to work the throttle and pray I make it thru an intersection, or wait for it to warm up before I leave the driveway. Details below.
When cold I've watched the injectors, using timing light hooked to coil wire as a strobe, and can see the injectors shutoff completely as the throttle is slowly moved from idle to about 50%. The right and left injectors will alternate spraying for 1-3 seconds (one side shuts off at a time). Engine falls flat, missing etc... This can't be normal right? Beyond 50% both injectors are pulsing continuously (not alternating sides), engine comes back to life.
When warm I've watched the injectors, both sides pulse continuously when walking throttle from idle to WOT, runs good, no flat spots.
Idles and runs decent when warm in closed loop.
Idles decent when cold in open loop, little to half throttle it falls on face in open loop, above half throttle in open loop comes to life somewhat.
When cold, before going into closed loop, part throttle is a dead spot.
I've watched the injectors, using timing light hooked to coil wire as a strobe, and can see the injectors shutoff completely as the throttle is worked from idle to about 50%. The right and left injectors will alternate spraying for 1-3 seconds (one side shuts off at a time)
No codes - flashes 12
Idle vacuum above 18.5" mg when warm and cold
base timing at 0* and steady wire disconnected, 20* wire connected
EGR is plated off, port at TBI capped, module hooked up
new parts - TPS, IAC, MAP, Cap & rotor, plugs & wires, fuel filter, both temp sensors - no change
All engine grounds clean and good, sensor grounds good
Am I looking at a computer issue??
ALDL cable is in the mail somewhere
Thanks,
Hack
This is a COLD engine OPEN loop problem only, all good when warm.
I have a 91 Suburban V2500 5.7L 4L80E
Basically when the engine is cold I have to work the throttle and pray I make it thru an intersection, or wait for it to warm up before I leave the driveway. Details below.
When cold I've watched the injectors, using timing light hooked to coil wire as a strobe, and can see the injectors shutoff completely as the throttle is slowly moved from idle to about 50%. The right and left injectors will alternate spraying for 1-3 seconds (one side shuts off at a time). Engine falls flat, missing etc... This can't be normal right? Beyond 50% both injectors are pulsing continuously (not alternating sides), engine comes back to life.
When warm I've watched the injectors, both sides pulse continuously when walking throttle from idle to WOT, runs good, no flat spots.
Idles and runs decent when warm in closed loop.
Idles decent when cold in open loop, little to half throttle it falls on face in open loop, above half throttle in open loop comes to life somewhat.
When cold, before going into closed loop, part throttle is a dead spot.
I've watched the injectors, using timing light hooked to coil wire as a strobe, and can see the injectors shutoff completely as the throttle is worked from idle to about 50%. The right and left injectors will alternate spraying for 1-3 seconds (one side shuts off at a time)
No codes - flashes 12
Idle vacuum above 18.5" mg when warm and cold
base timing at 0* and steady wire disconnected, 20* wire connected
EGR is plated off, port at TBI capped, module hooked up
new parts - TPS, IAC, MAP, Cap & rotor, plugs & wires, fuel filter, both temp sensors - no change
All engine grounds clean and good, sensor grounds good
Am I looking at a computer issue??
ALDL cable is in the mail somewhere
Thanks,
Hack
