Geronimo77
Newbie
Good morning,
To start, I have a 1991 (09/1990) K1500 Single Cab Step Side (Short Bed), 5.7L ~150K. One morning a few months ago I started my truck up to notice a rough idle and occasional misfire while driving, got a new check engine light on the way to work codes 32, 42, & 43. I have been tracking down the issue and have been running into issues finding it. I replaced the knock sensor, an obvious start, finding the old one looked to be in bad shape (loose/broken plastic tip). I check the wire for continuity and it tested and looks good. Problem persisted so I changed my CTS and ICM, the idle smoothed out considerably and on the initial test drive (warm day) it was perfect. Next morning to work (colder day) at intermediate throttle (in between babying it and giving it significant throttle I get a hard misfire; imagine taking a turn from a stop sign and trying to get up to 35 in medium traffic). This problem has been there since this issues started. I’ve checked my timing along the way and it sits smoothly at 2 degrees advances with the advance unplugged). I do have a significant exhaust leak from the exhaust manifold to y-pipe. I have it temporarily held together with the donut gasket in there. Just waiting on my shorty headers and y-pipe, and a decent day, to tackle that job. I didn’t know if that could influence the problem. I also don’t have an EGR, I bought it that way with an aftermarket intake manifold. Any suggestions on how to track down where this problem could be originating from? My next guess is ESC but I’d like to diagnose it vs throw parts at it. Any help is greatly appreciated.
Thank you,
Matt
To start, I have a 1991 (09/1990) K1500 Single Cab Step Side (Short Bed), 5.7L ~150K. One morning a few months ago I started my truck up to notice a rough idle and occasional misfire while driving, got a new check engine light on the way to work codes 32, 42, & 43. I have been tracking down the issue and have been running into issues finding it. I replaced the knock sensor, an obvious start, finding the old one looked to be in bad shape (loose/broken plastic tip). I check the wire for continuity and it tested and looks good. Problem persisted so I changed my CTS and ICM, the idle smoothed out considerably and on the initial test drive (warm day) it was perfect. Next morning to work (colder day) at intermediate throttle (in between babying it and giving it significant throttle I get a hard misfire; imagine taking a turn from a stop sign and trying to get up to 35 in medium traffic). This problem has been there since this issues started. I’ve checked my timing along the way and it sits smoothly at 2 degrees advances with the advance unplugged). I do have a significant exhaust leak from the exhaust manifold to y-pipe. I have it temporarily held together with the donut gasket in there. Just waiting on my shorty headers and y-pipe, and a decent day, to tackle that job. I didn’t know if that could influence the problem. I also don’t have an EGR, I bought it that way with an aftermarket intake manifold. Any suggestions on how to track down where this problem could be originating from? My next guess is ESC but I’d like to diagnose it vs throw parts at it. Any help is greatly appreciated.
Thank you,
Matt
