rough idle mystery solved

[CO2010ss]

my car has had a rough idle as long as I've owned it, I heard and read it was common so I never thought much about it, I put new plugs and wires in it yesterday and it is running noticeably smoother I figured it was because I went one step colder, was I ever wrong I was just looking at the plugs I pulled (the stock factory installed acdelco I assume being I bought the car with 40,000 miles) and noticed one was missing the tip.

[Clammy Clemens]

Ha, that's neat! My 2009 Cadillac SRX had the same problem with bad idling too. I had to replace 3 different spark plugs. Dealer was gonna charge me 2k to fix it, I did it under 400.

[My 5th]

I changed mine after 60,000 miles just because. Car was running smooth--nothing out of the ordinary. Over half of my plugs were worse than the one on the left. Go figure.

[PDXSSCE]

Originally Posted by Clammy Clemens

Ha, that's neat! My 2009 Cadillac SRX had the same problem with bad idling too. I had to replace 3 different spark plugs. Dealer was gonna charge me 2k to fix it, I did it under 400.

It was almost $400 to replace 3 spark plugs? Why?

[Jackass]

Originally Posted by PDXSSCE

It was almost $400 to replace 3 spark plugs? Why?

3 sets of plugs until he found the right set , plus the wires I'm assuming .

[jimlem]

OP - If you look at the inside end of the ground electrode (the piece directly across from the center electrode) you'll likely see it's a tiny bit thicker and has metallic deposits on it. That's where your center electrode went. By any standards those are extremely worn plugs. Car should run like new now.

[ron123]

The OEM AC Delco 41-110 plugs on the SS are Iridium tipped; the owners manual specifies to replace them at 97,500 along with plug wire inspection (2014). Although I will change mine out earlier!
OP mentioned the car was purchased with 40,000 miles on odometer ... what was the mileage when the plugs were replaced? They look like they are burning fairly clean deposit wise, heat range of the plug should be hot enough to burn off and prevent deposits on the center porcelain around the electrode and that part looks ok -- amazing the iridium tip is burned off. Were you getting close to the 100,000 mile mark when you replaced those plugs? (Noticed a full set of eight sell for $40 at walmart)

Ron

[CO2010ss]

Originally Posted by ron123

The OEM AC Delco 41-110 plugs on the SS are Iridium tipped; the owners manual specifies to replace them at 97,500 along with plug wire inspection (2014). Although I will change mine out earlier!
OP mentioned the car was purchased with 40,000 miles on odometer ... what was the mileage when the plugs were replaced? They look like they are burning fairly clean deposit wise, heat range of the plug should be hot enough to burn off and prevent deposits on the center porcelain around the electrode and that part looks ok -- amazing the iridium tip is burned off. Were you getting close to the 100,000 mile mark when you replaced those plugs? (Noticed a full set of eight sell for $40 at walmart)

Ron

had/has only 44,800 miles those plugs according to gm standards should not even be at half their lifespan, the other 7 looked good just like the one on the right.

[christianchevell]

Iridium is brittle thus no gapping the plugs or you can damage them, that and it just being a wire basically in the center of the porcelain it may have broke off from just being fragile and you hit a bump one day... I see your running the right ones now tr6ix though many swear by the originals they are iridium also. Beefing up a ride its one of the things that require more maintenance also as it shows the condition of the motor and the burn... I have a set in my glove box just incase I check them some time and don't like the fouling or condition of them though they are not cheap its better to have a set on hand than hope to find them in stock at parts stores.

[JCunningham]

That looks like antiseize
on the threads I bet the previous owner tryed to gap them for some dumb reason. If you use a regular gaper you will wipe the iridium off and break the tip.

[ron123]

Originally Posted by JCunningham

That looks like antiseize
on the threads I bet the previous owner tried to gap them for some dumb reason. If you use a regular gaper you will wipe the iridium off and break the tip.

The plug manufacturer agrees ...
This is from the AC Delco website:
"Use the correct deep socket size to loosen each spark plug one or two turns.
NOTE: To remove spark plugs from aluminum heads, allow the engine to cool. The heat of the engine, in combination with a spark plug that is still hot, may cause the spark plug threads to strip the cylinder head upon removal.
Brush or air-blast dirt away from the well areas before removing spark plugs.
Remove each spark plug and place each one in a tray by cylinder number. This will help identify and relate any unusual condition to the cylinder involved.
Apply dielectric grease into the boot area to reduce the chance of exterior tracking on the buttress tower of the spark plug. This grease also promotes a good heat transfer between the spark terminal screw and boot terminal.
Before installing new spark plugs, use a gap guide to make sure your new spark plugs have the correct gap.
NOTE: ACDelco Professional Iridium Spark Plugs are pre-gapped during manufacturing. Never attempt to gap an ACDelco Professional Iridium Spark Plug. You could damage the spark plug. Replace the incorrectly gapped ACDelco Professional Iridium Spark Plug with one that is correctly gapped.
One-piece suppressor seal blocks radio frequencies that can affect vehicle electronics.
Suppressor seal meters spark energy for longer electrode life and seals against combustion leakage.
Iridium composition has the highest melting point and strength of all metals. It provides the greatest wear resistance and durability over Platinum and Conventional spark plugs. ACDelco Professional Iridium Spark Plugs provide the best wear resistance and durability of any spark plug."
http://www.acdelco.com/auto-parts/sp...ark-plugs.html