1999 88 3.8 Where the oringinal plugs platnum or iridium?

[Ratt643]

Been some time since I last posted but running into problems with this Olds 88. The car started having a slight miss, owner thought it might be water in the fuel. He ran some Seafoam thru it, and it straightened up. Not long after that, the upper intake exploded when the key was turned on. I replaced the upper intake and fuel pressure regulator carefully following the directions with the new intake. I keep getting a misfire code #2 cylinder and occasionally #1 misfire.
I bought a HEI tester and tested all the plug wires, which were installed just a couple of months ago, all fired. Checked all the coil towers, good spark. Took the ignition module to a FLAPS and had it tested. Three test all show pass. I then used my multimeter to ohm all the injectors. All six showing 12 ohms. The fuel filter was replaced about two years ago and this car is not driven that much.
Now to the spark plugs. Counter guy at the FLAPS said it required Iridium spark plugs. The spark plugs in it are regular copper core gapped at .060. These were replaced at the same time as the wire, recently. I am going to put a set of Iridium plugs in it, thinking something happened either before the intake exploded or when it let go. I don't believe it has a vacuum leak, it idles at 750 rpm.
So , does anyone know if these engines came with Platinum or Iridium plugs or just the run of the mill AC Delco copper core plugs?

[Tech II]

They certainly don't come with copper core...should replace with OEM.....any parts department should be able to give you the correct OEM plugs...

But you still aren't out of the woods.....you say you tested the wires/coils with a spark tester, and it was ok......could be a compression problem or injector problem....since plenum was replaced, could also be a lean misfire due to improper installation.... could also be a back pressure problem with the cat unseating the EGR....

[Ratt643]

Thanks Tech,
I replaced the plugs this morning with AC Delco Iridium plugs and cleaned the mass air flow sensor with electrical contact cleaner. Took the car for a drive and it did run better up to 3/4 to full throttle. Then the misfire started and the Check Engine light illuminated.
After I got it back home, I pulled the code and had a #3 cylinder misfire. I swapped the #5 coil and the #3 coil. Went for a test drive and sure enough the misfire followed the coil pack and showed up on #5. So tomorrow, I will replace the #3 coil pack and go from there.
It could still be an injector issue, I would have to pull them and take them into Knoxville and have a diesel place check them out, about $100. I am wondering if any of the local auto parts stores have a fuel injection cleaner kit that I can rent. I replaced the EGR standpipe with the one that came with the new intake. I cleaned the intake mating surfaces and installed the intake per the instruction so I don't believe I have any vacuum leaks. if I did, I think the engine would idle high, this one is not.
Thanks for the tips, I'll hopefully post tomorrow how it goes with the coil change.

[Ratt643]

The coil pack did the trick. No misfire and no check engine light. Thanks and hope this helps someone out down the road.