Engine Car is idling rough and cutting out

[keel]

Just finished an engine rebuild and the car ran perfect for about 500 miles or so, but now it is intermittently running poorly (doesn't seem mechanically related). Initially, it was idling low and rough and would cut out under load and buck occasionally, and the CEL came on. Then the CEL would turn off and the car would run as if nothing happened. This continued for about 10 minutes until I got home. I dumped codes when I got home, and got 67, 81, 82, and 84. However, before it dumped those codes, the CEL flickered briefly. Not really sure what that means but might be important to include.

I understand that these are EGR codes, I have deleted the EGR system completely and have been running an EGR eliminator plug that I got on LMR a while ago that they no longer sell. It has worked great for the last 3 years.

What could be the issue?

 

[General karthief]

You have a wire connection issue. I would start with the ignition wiring looking for bad connections/cracked wires.
Start by wiggling crap.

 

[General karthief]

You have a wire connection issue. I would start with the ignition wiring looking for bad connections/cracked wires.
Start by wiggling crap.

 

[AeroCoupe]

So a Code 67 has nothing to do with the EGR but I doubt it’s the cause of you issues. See Post #2 in this thread:

Code 67

1988 Mustang factory V8, 5 speed car. Mass Air conversion done with A9L computer. When KOEO is done I get code 67 along with some EGR codes too. Trying to fix the 67 code. When codes were pulled a/c was off, car in neutral and clutch pushed in. A Tr 3550 tranny is in the car and the sensor...

stangnet.com

 

[keel]

Agreed with the wire connection issue, drove the car today and it had absolutely zero problems, no CEL either. I'll go over the harness.