1996 Buick Roadmaster idling and skipping issues.Video posted


Asked by Sep 03, 2014 at 01:50 PM about the 1996 Buick Roadmaster 4 Dr Limited Sedan

Question type: Maintenance & Repair

I have a 1996 Buick Roadmaster 350 LT1 5.7, I am having some issues with the vehicle idling rough and seems to be missing. When I turn on the AC the car runs a little better and sometimes after shutting the AC OFF THE CAR SHUTS OFF.I went to AutoZone and had my car put on the computer and I got a EGR code P0400, Mass Air Flow code P0100, and a Catalyst code P0430. I replace the EGR, and mass air flow sensor, and my car is still doing the same thing. I was also told I may have a leaky water pump. I just recently installed new AC DELCO plugs and wires and a new air filter. Any ideas on what to try next or what could be my problem?

Here is a video of my car running.

6 Answers


Does your car have a distributor cap or electronic ignition? If, at its age, it still uses a distributor cap to manage spark timing, I would try replacing it and having the engine timing set to spec.


I have already replaced the opti spark about 2 years ago....


Ok here is how this game has gone with my 96 Roadmaster wagon. I did hear you that you replaced the Opti spark, BUT When the water pump leaks the coolant leaks onto Distributer that was so cleverly mounted behind the water pump. The coolant will deteriorate the distributers seal and get into the electronics thus causing all kinds of issues. I have lived this situation at least 6 times (cheap water pumps) with my roadmaster wagon. Do the water pump (buy a good quality AC delco or Delphi) and check the distributer. Clean the coolant off of the wires this stuff will break down the wires too.


Another thing to check is that the wires have not become melted against the block from being up on the exhaust manifolds. they will short out causing a miss as well.


UPDATE!!!!!! After replacing the EGR and Mass Air Flow sensor I did not unplug the battery cable to reset the computer, so after doing that the check engine light went off for about 2 days and it came back on yesterday so I went to AutoZone and had it placed on the computer and the only code I got was the P04030 indicating that the Catalytic Converter is bad. I wonder is the code just a reference to a bigger problem or since it is the only code showing up ,is that my problem the actual CAT CONVERTER?Should I go ahead and replace it?


The cat converter could be bad because of the first two issues you had. If they are run too lean they over heat and fall apart internally. If you where running too rich they melt and restrict the exhaust. The second situation will throw a code. But I would check to make sure before spending your money. Cat converters are expensive and your car has two!

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