Impossible fix for a Code 42 !

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JTWard

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SE Pennsylvania
First Name
James
Truck Year
1990
Truck Model
C1500 Silverado
Engine Size
350 Gasoline
I'm new here, but I wanted to shear my experience dealing with a problem I was having with my 1988 K5 Blazer which I spent the last 2 years restoring. My 88 Blazer with a 350 ci. has had a code 42 which totally baffled myself and the shop I use. Tried everything, but I finally got rid of the Code 42 by a forum member on another site. I have a new distributor and I added a MSD 40.000 volt coil. Had everything checked and nothing would fix the code 42, till my friend a GM Senior tech at a GM dealership. All I did was , as per his instruction : " Take off the negative battery cable, then the distributor cap and remove the rotor, look at the 'Ignition module' If it's white, take it out and throw it away, If the ignition module is a red or a hi-performance ignition module, take it out and throw it away. Get a AC Delco ignition module, wipe the base plate clean with Acetone and wipe any grease or oil off the 2 hold down screws. You get a packet of white paste, cut it open and spread the paste onto the bottom of the new GM ignition Module in a amount of about the size of a large postage stamp. reinstall the module and screw the two screws down to finger tight and then go 1/8 inch more. all the 3 connections connected, and button up everything. Reconnected the negative cable and started the engine. Fired up the engine it ran fine, no lights, let it go through open loop and into closed loop, ran till temperature was fully up to temp. No code 42 and it ran fine, slight rough idle.

So I replaced the yellow plug wires with a set of AC Delco professional wires and I took out the stock R43CTS plugs and put in a set of AC Delco 'Rapidfire Platinum #1 spark plugs. I felt the wires were too close to the exhaust manifolds, so I took a set of insulators, cut them to fit and used super glue to keep them from flaking apart. Now Start in a mill-second with a turn of the key Idles like a new engine. I think and feel the swap of the cheap wires & old stock plugs made the main difference. The R43CTS were gapped at 0.35 and the new Rapidfires at 0.45. I felt the MSD coil wasn't being allowed to get a full charge to the plugs.
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gpmorgan

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Tupelo Ms.
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greg
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632
Great post JT.
 

JTWard

Full Access Member
Joined
Mar 3, 2017
Posts
78
Reaction score
73
Location
SE Pennsylvania
First Name
James
Truck Year
1990
Truck Model
C1500 Silverado
Engine Size
350 Gasoline
My friend said that this will fix 70% of your code 42 issues ! Sure as HeL& with mine. I should mention that the biggest impact to the idling, running and performance aspect has been the AC Delco rapid fires plugs and the GM Performance wires.

I forgot to add the ignition Module part # AC Delco D1984A

Backup GM# 19179580
 
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