Spark Plugs

[rkn2903]

I have a 99 GMC 5.3L Ext. Cab, and I just replaced the plugs with AC Delco Iridium Spark Plug and my truck at start up seems to idle a little rougher now with the new plugs in, I don't know if it's because the weather being colder or not and it idles higher and longer on start up also. Have anyone else used these AC Delco Iridium Spark Plug in there truck?

[budhayes3]

I haven't heard anything bad about the Delco Iridiums, I use the Denso Iridiums myself, with no problems. You might want to check and make sure that none of the porcelain insulators are broken and make sure that they're gapped right. From what I've read, the iridium plugs don't use the factory gap spec of .060, and they should come pre-gapped at .040.

 

If you re-used the old wires, you might want to check them with an ohmmeter also. One or two might have gotten damaged upon removal and may have high resistance.

 

One last thing, if it's idling higher than before, that could be the PCM compensating for a reduced engine power problem, or the hose to the PCV or some other vacuum line may have come loose. Good luck, hope your diagnosis is smooth and easy!

[Valsport]

I just installed the delco iridiums and I didn't notice a rougher idle. Might try doing a top end cleaning with some seafoam.

[lip277]

Ummm....

Might have screwed up one of the spark plug leads....

 

When I replaced my plugs last summer, I also replaced the leads at the same time.

 

I used OE Delco parts for both and it runs GREAT. Almost don't even know it's idling still now (and 87,000 miles....)