C4 General Discussion General C4 Corvette Discussion not covered in Tech

Timing issues

Old Mar 10, 2025 | 09:52 PM
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Zach James's Avatar
Zach James
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From: Los Angeles
Default Timing issues

This just started few days ago but here is my issue with 91 C4 L98 65k miles

Ive Check fuel pressure and everything checks out fuel pump etc injectors are new as but double check everything and it all checks out

set base timing like 3 times replace spark plugs as I had spares and changed wires as well, rotor and cap look good and was replaced few months ago and replaced the icm as well, copper plugs gapped even re gap them just to be sure

one thing I notice is that base timing jumps up about 5 degrees when EST disconnected when trying to set base timing it will be steady and jump up from time to time and rpm increases with shift in timing

if I’m just cruising around it it runs fine but once I try to get in it and or use lower gear to get in higher rpm the car breaks up and power decreases and can’t really accelerate and then power comes back then breaks up again when I just cruise everything is fine I mean I does break up a lil here and there but It’s only really noticeable accelerating and high rpm

what I’m a missing cuz this got my head scratching
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