Friend of mine has a 90 Olds 98. It wasn't running good for her so she brought it over and we changed the spark plugs, oil, filters, etc. It starts, & runs, but seems to be missing. Could someone tell me what the firing order is so I can check that? Cataletic (sp?) converter seemed to clog up right away and I was told to check the firing order because it shouldn't have clogged up like that.
Firing order is 1-6-5-4-3-2. Some GM V-6's have DIS, in which case make
sure the plug wire is attached to the proper terminal on the coil pack
Check the trouble codes
Something is misfireing dumping raw fuel into the cats. Lift the spark plug wires from the plugs one at a time and replace it - what you are trying to do is to isolate the cylinder not firing by seeing which plug wire being lifted does not cause the engine to run worse. This will lead to further diagnosis of bad plug, plug wire, coil pack or distributor cap, etc.. if this further electrical diagnosis shows no electrical problems, we move towards fuel injection issues or manifold leaks causing too lean of a mixture to ignite.