Hello, new member here. I have a 96 Deville with the northstar engine and having surging problems after the engine warms up. Dealership could not locate what was causing the problem and a local repair shop thought replacing the intake gaskets would fix it because they suspected a leak.After changing the intake gasket thiswas also unsuccessful. I would welcome any ideas for what might be causing this surging, thanks.

Have you tried pulling the codes? If not, please do so and tell us about'em.

I have seen more than one 96 year model with idle problems caused by a faulty PCM.
Unfortunately all other possibilities need to be eliminated before condemning the engine computer.

Thanks for the replies so far. I should clarify that the surging is while driving and not at idle. I assume the dealer already pulled the codes when it was in for this problem if there were any. I did not ask for them or what they were, regardless they were unable to locate the problem.