Do my spark plugs go bad due to age and excessive use of fuel injector cleaners?

[DriveHard]

Have you checked engine operating temperature?
The thermostat could be sticking.

Pretty sure it will throw a code if the temp doesn't get up to where it should be

 

[easym]

Pretty sure it will throw a code if the temp doesn't get up to where it should be

Do fuel injector cleaners cause carbon fouling in the sparkplug?

 

[Jimmy_Russells]

Do fuel injector cleaners cause carbon fouling in the sparkplug?

No

 

[Oillover]

Do fuel injector cleaners cause carbon fouling in the sparkplug?

I had an 86 Corolla I used too much carb cleaner on in an attempt to fix a rough idle.
My mechanic fixed the issue by noticing and fixing the vac leaks.

It continued to run rough (but better than before). At that point he told me to change the plugs.
Sure enough, the excessive carb cleaner actually formed snot-colored hardened chunks on them.
After replacing them, it ran like a dream.

Like others have suggested, change the plugs to AC's.
After 7 years, the current ones don't owe you anything.

 

[GMBoy]

A few posts suggest the Autolite plugs are the issue - highly doubtful. Also AC Delco plugs are made by various makers such as NGK, Denso etc so again - nothing special and no need to run "only AC Delco plugs". I would recommend, if you replace plugs, to run a double platinum plug and autolite is just fine as is NGK and others.

 

[eljefino]

Check for a dragging brake:

Warm the car up, so you've warmed up the wheel bearings and scraped the rust off the brakes. Drive up a gentle hill and throw it in neutral. If you have a dragging brake you'll feel it when the car transitions from going forwards to backwards.

You can also use an IR temp gun to see if one wheel is hotter than the rest after driving.

 

[Blueshound]

Former mechanic and 3800 owner here. That's a normal-looking O2 sensor in my opinion, and you said it was cycling normally. I suspect your fuel efficiency woes are elsewhere. Is the engine low in power? Could be a plugged cat. As long as you're checking the brakes with a temp gun, might as well shoot the cat too. And give it a couple of love taps to be sure the catalyst isn't rattling around inside. It should temp at least a couple hundred degrees higher than the downpipe. If not, well, it's up to you what to do about that....

 

[easym]

Former mechanic and 3800 owner here. That's a normal-looking O2 sensor in my opinion, and you said it was cycling normally. I suspect your fuel efficiency woes are elsewhere. Is the engine low in power? Could be a plugged cat. As long as you're checking the brakes with a temp gun, might as well shoot the cat too. And give it a couple of love taps to be sure the catalyst isn't rattling around inside. It should temp at least a couple hundred degrees higher than the downpipe. If not, well, it's up to you what to do about that....

I put a new denso oxygen sensor my mpg got reduced from 16 mpg to 15.5 mpg. The engine power is alright. May be a I will change the sparkplug and check the catalytic converter.

 

[easym]

I changed ICM recently, my mpg got so much better. It seems like ICM was on its way out. When I changed my coils, I didn't change my ICM. It seems like it is a good practice to change ICM and coils together.

 

[wlk]

I would also run AC Delco plugs but not iridium, my old 3.1l v6s are copper oem and actually run better on copper than platinum or iridium, tried both over the years. Not sure which is oem but if copper I'd run that esp if it has the old waste gate ignition. $.02.