I have a 1990 cadillac deville with a 4.5 liter that ran great until the diverter valve needed replaced. I've looked online and read the same words in every link i look at... The part is obsolete! and no after market diverter valves were made.

  Is there a way to bypass the diverter valve so I can keep a perfectly good car running??? This is a one owner car with no rust, all original, clean and an all around classic!

  Please help!
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John L.
I am not familiar with your problem, but I like to research and learn about different things.  I found a couple things below if you are interested.  I saved your main answer for last.

1) If nothing else caused the diverter valve problem, have you considered trying a salvage yard?  I read about a place called Cadillac Heaven that is supposed to be all Cadillacs.

2) I read that the solenoids in the diverter valve could be the problem.  Maybe they could be fixed or gotten from another GM vehicle?

3) I don't know if it is legal or not, but it might not matter since your car is older.  I got this from

"If you can live with the check engine light that will never go away, it's easy. Remove the diverter valve and all of it's piping. Plug the leftover holes in the exhaust manifold and cat converter.

To delete the air pump as well, copy GM did when the removed the system in the 4.9 - remove the pump and go to the junkyard to obtain the bracket GM put in it's place. Then head over to the parts store and buy a belt that is the correct length for a '91-'95 4.9L."
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