troubleshooting a 1993 3.8L supercharged CODES 42, 55

[Bones]

Code 42- PCM has detected a grounded or open Elect Spark timing bypass circuit of the C3I Distributorless Ingnition (DIS) module

Code 55- PCM did not see an expected RPM drop when it tested one of the two EGR solenoids controlling the EGR flow.

This is on a 93 Park Avenue.

Sounds like a bad EGR valve, or bad PCM. My question is would these 2 codes be related, or are they 2 seperate issues? Any guesses on what to replace? This is on my Dad's vehicle.

[Yetti]

I would be checking for a bad spark module. its mounted under the coil pack, if its running rough it could as easy as a coil pack. cut 6 pieces of vacuum hose 1 1/2" long and remove the plug wires one at a time and insert on the coil outputs and plug the wires in over them. use a test light while its running to to touch each one and see if it kills the cylinder, if you don't get a spark out a pair of outputs then its just the coil.
if a pair of out puts is dead then swap coils from another position and see if they are still dead, then it would be the module.

as for the EGR code remove the valve and see if the seats plugged with carbon, re install after you clean it out.
if its non vacuum egr then you have to be very careful not to damage the seating surface.

[Bones]

thanks Yetti

I should also mention that it ruins fine for a while, then craps out. So far it hasn't died completely... it will just run crappy, we can turn it off, restart it and it will run fine (or as well as a car with 280K miles will run)

[Yetti]

Originally Posted by Bones

thanks Yetti

I should also mention that it ruins fine for a while, then craps out. So far it hasn't died completely... it will just run crappy, we can turn it off, restart it and it will run fine (or as well as a car with 280K miles will run)

It may be a heat related open in a circut in the module.