Oldsmobile/Buick Repair: 91 Olds Cutlass Supreme 3.1L, olds cutlass supreme, egr systems

Question
I have a 91' Old Cutlass Supreme with the 3.1
I was pulling an EGR code 12. The car was suputtering and kinda missing during idle and driving. I pulled off the EGR and cleaned it. I tried blowing through it and could not. I did see however alot of build up in the exhaust manifold where the EGR valve bolts too the top of the block. Sinse you really can't just chip it off and leave it in there I pulled the top portion off. The hole where the EGR blows through should be about the size of your thumb but was so built up there was maybe a 1/8" opening. I cleaned it out, relplaced the PCV valve and hose. Which might I add was kinda a dumb design i think. Now I have everything together again and it's still doing the same thing. The plugs were changed at the same time. Wires SEEM to be good but I'm gonna do that next just because. This car has always kinda missed during idle and sometimes wanted to stall at stop lights while in gear. I was going through the Chiltons on this and it gave a couple options. Clogged cat, plug wires, bad EGR, vaccume, and such. Besides the fact that the car idles at 35mph it still misses. I was just getting on the highway one day and there was no power. Car was spuddering trying to get up to speed. Kind of like not all cylinders firing. Any help you could give me would be great. Cars got 138000.  

Answer
If the CHECK ENGINE LIGHT is NOT illuminated on the dash then the CODE 12 you are getting is NOT a FAULT code caused by the EGR system.

The code 12 has 2 DIFFERENT meanings. If the CHECK ENGINE light is NOT ON then the code 12 will be displayed ONLY 3 times in sequence and this indicates that the computer code display system is operating properly.

If the CHECK ENGINE LIGHT is ON and you get this CODE 12,  6 times in sequence then you would have a code 12 EGR systems fault.

I would perform a BACK PRESSURE test on the exhaust system as it is highly likely that you may have an exhaust restriction most likely in the catalytic converter.


NOTE: The CHILTON'S book is very VAGUE and is NOT very reliable for performing accurate diagnostic procedures as it is ONLY for general information ONLY. I have well over 100 manufacturer's service manuals that I have purchased over my carreer and I would NEVER own a Chilton's or Haynes manual for just this reason.

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