Rough idle, Timing randomly adjusts

[tayto]

The Ignition Control Module(amplifier)is mounted on the distributor and both early and late EEC's use the same one. The early Electronic Spark Control is about a 3"X3" box normally mounted on the right side intake man. beside the TB. When retrofitting a late ECM into an early truck you would bypass the external ESC and toss it. If they didn't it may create strange ignition timing issues.

i would put money the stock ECU and 305 chip are in this thing.

 

[ChevPasmore]

The Ignition Control Module(amplifier)is mounted on the distributor and both early and late EEC's use the same one. The early Electronic Spark Control is about a 3"X3" box normally mounted on the right side intake man. beside the TB. When retrofitting a late ECM into an early truck you would bypass the external ESC and toss it. If they didn't it may create strange ignition timing issues.

Ah, I do not have a 3x3 box mounted next to the TB. At this point I’m ready to swap out to an older 350 and go carb setup haha

 

[ChevPasmore]

i would put money the stock ECU and 305 chip are in this thing.

Most likely lol. Can I just swap in a 350 chip or do I need the ecu as well?

 

[tayto]

In 1995 the $0D ECM code running on ECM p/n 16197427 was common. If your swap included the ECM, I would expect to see a sticker on it bearing "16197427". You might read the four digit code of the blue MEMCAL (or was it CALPAK?) and report it here; it may not be the ideal one for your application.

considering he said the 1990 harness was retained, I highly doubt this. Also we have NO idea what transmission was behind the first 5.7L. if it was from a manual transmission itnwoild have used the older ECU reguardless if it was from 94-95

 

[tayto]

Most likely lol. Can I just swap in a 350 chip or do I need the ecu as well?

yea you can do just the chip or the whole ECU as long as long as it is compatible

 

[1998_K1500_Sub]

considering he said the 1990 harness was retained, I highly doubt this.

I missed that detail, good catch.

(edit) Yeah, I see it's right at the top of post #1, duh. I saw the comment about "ECM" in post #14 and that was my trigger.

 

[tayto]

considering he said the 1990 harness was retained, I highly doubt this. Also we have NO idea what transmission was behind the first 5.7L. if it was from a manual transmission itnwoild have used the older ECU reguardless if it was from 94-95

for your year the ESC (electronic spark control) module was mounted on the intake on the passenger side. it will have a 4 or 5 pin flat connector going to it. this also is engine dependant and has a code on it as well. but one thing at a time....

 

[ChevPasmore]

for your year the ESC (electronic spark control) module was mounted on the intake on the passenger side. it will have a 4 or 5 pin flat connector going to it. this also is engine dependant and has a code on it as well. but one thing at a time....

Ah yes, I have that and pulled a few things out of the wrecker today. I will match the codes between the two lol. I’ll get the ecm number and all that tomorrow for reference

 

[tayto]

You must be registered for see images attach

 

[tayto]

Ah yes, I have that and pulled a few things out of the wrecker today. I will match the codes between the two lol. I’ll get the ecm number and all that tomorrow for reference

I believe the 5.7L module is code "HKR"