Emmisions help

[98Raven]

Hello everyone. I hope you can help me out, well my friend. One of my friends has an 88 caprice v6 (all I know from his emmisions paperwork). He Did not pass emissions due to his NOX (oxides of nitrogen). He had a 2.7 and the most you can have is 2.5. They said it was more then likely the EGR and Cats that need to be replaced. After speaking with one of my other friends he is 100% sure its the EGR and not the cats. My question is how hard is it to replace the egr on a 88 caprice, and do you feel same about what my other friend said about not being the cats?
Thanks again guys

[89iroctpi5.7]

Not sure onthat car how hard it is to get to. Should be behind the carburater its round kinda saucer shape with one vacuum line going to it.You should be able to reach your finger under it and feel the diaphram. With engine running feel under it and move the diapham up the motor should idle poor if it is working. also rev the motor while feeling the diaphram it should move up and down while you rev the motor. let us know

[silicon212]

Originally Posted by 98Raven

Hello everyone. I hope you can help me out, well my friend. One of my friends has an 88 caprice v6 (all I know from his emmisions paperwork). He Did not pass emissions due to his NOX (oxides of nitrogen). He had a 2.7 and the most you can have is 2.5. They said it was more then likely the EGR and Cats that need to be replaced. After speaking with one of my other friends he is 100% sure its the EGR and not the cats. My question is how hard is it to replace the egr on a 88 caprice, and do you feel same about what my other friend said about not being the cats?
Thanks again guys

There's much more to it than that. On the EGR system, there could be several things to look for:

EGR Valve: Pintle moves freely and does not bind against carbon buildup. The diaphragm is not shot. You can test this by removing the valve and pressing in the pintle, and releasing. It should return to its non-vacuum position. Press the pintle down again, this time place your thumb over the vacuum line attachment, sealing it well, and then release the pintle. It should NOT move into the non-vacuum position - if it does, the diaphragm is shot and the valve will need replaced. A new valve on my '88 9C1/5.7L cost me $95 direct from GM - these are not cheap. If the pintle binds, lightly tap it with a hammer to dislodge carbon buildup.

EGR vacuum solenoid - a failure in this can, but does not always, set a trouble code (service engine soon light).

EGR vacuum lines - make sure there's vacuum at the solenoid when the engine is running - pull the vacuum line off and place a finger over it. If you feel suction here, it's working. With the engine warmed up, you should feel suction at the valve end of the solenoid.

If the smog pump is not working, this will cause a spike in NOx emissions - the catalytic converter is fed air in a tri-cat to catalyze the NOx. If this air is not present, the cat can't do its job. Check the check valve on the line going down to the cat to ensure it's not plugged with carbon.