1989 GMC S15 Missing throughout driving range.

1989 GMC S15
19,000 MILES • 6 CYL • 4WD • AUTOMATIC
Avatar
LASZLOMANN
  • MEMBER
  • 1 POST
I've done a complete tune-up, plugs wires, rotor and cap. Changed the fuel and air filters. about a month after this the truck started to hesitate while accelerating and on long trips will sometimes shut off and not start for 10 minutes. I did a computer check and I'm getting a code 42. Probable cause: Electronic Spark Timing bypass circuit or Est circuit is grounded or open, A malfunctioning HEI module can cause this code.

So here is my question. I have the Haynes manual but I can't find out WHERE these circuits are located. Also is the HEI module a fancy way of saying distibuter cap? I need this truck to run and I've spent days on this. I'm broke so I have to fix this myself. PLEASE help. I'm a plumber not a mechanic so please explain it like you're talking to a child.
Thank you.
Oct 10, 2008 at 8:06 PM
Advertisement
Avatar
SWILLIAMS
  • ASE Certified Mechanic
  • 597 POSTS
  • ASE Certified Mechanic
HEI is the ignition module located in the distributer. They show those symptoms when they are failing. When you install the new one make sure you apply the heat conducting grease they will include with it. Clean the connectors as well. Good Luck.
Oct 13, 2008 at 8:38 PM
Join 2CarPros for free, one of the most advanced car repair communities on the internet. From first-time drivers to seasoned mechanics, everyone is welcome to reply, share details, and get better answers. You can add a temporary image or video first; uploads are limited to 20 MB.
Ask a Free Question
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.