deadguy

I posted this in the maintenance section but wanted to put it here as well for those who visit this section exclusively.

I decided this past weekend to do a little driveway maintenance on my LS, which included cleaning the MAF sensor, the throttle body, and changing out the spark plugs.

The old plugs were almost impossible to remove due to the buildup on the threads. I don't know much about plugs and how they should look after 123k miles, but to me, it seemed like there was quite a bit of carbon build up on a few of them. After completing all of these tasks, I noticed that the car does idle lower in park (~700rpms), and while in gear at a stop (500rpms). Acceleration seems a bit better, and I plan to test gas mileage when I can get to the interstate. Previously I was getting an average of 27mpg at 78mph.

Pics of the plugs.

alanchad

iTrader: (1)

It would be nice to see a side by side comparison with a new plug to see wear.

Thanks for posting.

Alan

2KHarrier

Yeah, I'd say those are about done... The build up is probably from the fuel you're using. It may have additives in it that arent being burned off.
The tip, or Center Electrode, should be a little longer, and as a result of firing countless times over the last 10 years, has worn down.
The Ground Electrode doesnt look too bad, though...

Most importantly, they're not wet with oil, so you don't have to worry about ring problems.

deadguy

Would the buildup cause the car to give off a sulfur smell when accelrating heavily? I ask because since the cleaning and plug change, I have not detected the sulfur smell at all.

2KHarrier

That's possible. Under heavy acceleration, the ECU dumps more fuel into the cylinders, to allow for more power, and with the plugs not working at their optimum capability, you may have been experiencing some improprer burn, resulting in the sulfer smell coming from the converters.

Usually the computer will compensate for that by retarding timing, or reducing the fuel output when it detects cooler temps (via the O2 sensors) coming from the converters, though.

KING

iTrader: (1)

Good work. Those look like they've done more than they were asked to do.

Props to the great camera

Lavrishevo

iTrader: (1)

Yours definitely looked in rough shape. The threads especially. These were mine at about 110k.

https://www.clublexus.com/forums/ls4...ml#post8358807

deadguy

Thank you, sir. Amazingly, these pics were taken with my cell phone! I was surprised myself at the quality.

lorenr

iTrader: (1)

But even though they look good and have done more than what was required of them, they still should have been changed at 60,000 miles.

Plugs are cheap, very cheap.

You, however touched on the problem. There removal. If the threads in the cylinder head (remember they are aluminum) are damaged when they are removed, then the new plugs may not install correctly and that can be very bad. The problem arises because even though the spark plugs and cylinder head are dissimilar metals, they will still try to bond to one another. The longer the plugs go unchanged the greater the risk.

Change them at 60 K or be VERY careful.

deadguy

no records show that the previous owner changed them, but they will be every 60k from now on.

KawiLex

Hey, after I disconnected the battery, attempted to spray clean the MAF(can't really touch those wires so can't really call it a cleaning IMO), then cleaned the throttle body.. the car idled high for a little while and now while in drive I think it idles too low.. around 400-500rpms after warm up..

Any ideas on that? My plugs are the long life ones that were changed 30k ago.. just inspected and cleaned any minor buildup on them.

I run some chevron techron through the fuel system once every few months.