Trying to troubleshoot a recurring error code, mainly on cylinder #1 (P0301) but sporadically get random (P0300), #3 (P0303), and #5 (P0305). Changed plugs, cap/rotor, and distributer/plug harness but still throwing codes. Upon further inspection I noticed the heat wrap on the underside of the ECU wiring harness is gone (see 1st photo) so I'm moving on to diagnosing those wires for any damage/shorts. So far I tested the connectivity between the injector terminals and the ECU on cylinders 1 & 2 (will do the rest when I have time to clear the obstacles above to get to them) and both lines seems fine, even when I wiggle the harness around where the heat damage has occurred. One thing I discovered in this process is that PO installed an aftermarket Code Alarm CA5153 alarm system that has a wire clamped onto the white/blue cylinder #1 wire in the ECU harness (see 2nd photo of red clamp leading to purple wire that runs through firewall to the alarm control box shown in the last photo), so I'm wondering if that might have any impacts. I've owned truck for 3 years and never had any problems with the alarm, and cylinder misfires are fairly recent. I'll move on to other steps in diagnosing misfires (closer inspection of the heat damaged harness, dirty/stuck injectors, air/fuel mixture, etc.) but thought I'd ask if anyone has experienced similar condition with the alarm (I have zero knowledge of alarm set ups but I'm guessing there's a reason the alarm monitors the signal from ECU to cylinders during operation). Thanks in advance!
