Spark Plug Wear - after 50K miles of use (1 Viewer)

[Romer]

Here are the specifics:

1997 LX450 - Plugs last Changed in Nov 2005 at 108K Miles

Current Mileage is 154K Miles

1FZE engine - Headgasket, valves and injectors done in Nov 2005

SC Added along with Supra Fuel pump in June 2006

Lantank MAF and Snorkel added in 2007. Also Aux tank added in 2007.

I was running stock Plugs. I replaced these today with the Platinum plugs for an MR2 (Cdans recommendation for SC).

I do a mix of driving, some very long trips at high speed. 1-3 times a week lots of city traffic to and from work.

Recently, I was smelling what I guessed was unburnt fuel in the exhaust when I started up. To me that said the plugs were fowl and not burning all the fuel. The results show that likely to be the case. Additionally, my gas mileage has gotten worse over the last few months. Didn't take notes, but I could tell it was trending downward, maybe 20 miles a tank (Just main tank).

After changing the plugs, I could tell it was running a bit different, higher idle like when you unplug the battery, but only slightly higher.

Thought, either I am running rich, or after the plugs deteriorated to the point it couldn't burn all the fuel, the darker covering occurred. Could also be that after the add in of the SC, the stock plug heat range was no longer appropriate.

In case the pictures don't show it well. Main terminal is black, Electrode is dark brown and so is the ceramic around the center terminal.


Doing a google search, this is what comes up

"Can be caused by many different conditions. Carbon deposits build up when the plug fails to fire correctly and burn them off. Air/fuel mixture too rich, choke stuck on, electrical problem, extended periods of low speed driving, plug heat range too cold. All should be investigated"
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Everything is running fine with the new plugs, take a while to see if the MPG goes back up. Just thought I would share with some long term data that's much better than seat of the pants info

 

[Buckru]

Ken,

Did you ckeck any of the old plugs to see if the gap had changed?

Buck

 

[bpassmore]

Your top plug looks normal in that pic. (light tan is to be expected in my experience)

your bottom plug does appear to have been run rich for a long time.

 

[Romer]

Haven't checked the gap to see if they changed

Your top plug looks normal in that pic. (light tan is to be expected in my experience)

your bottom plug does appear to have been run rich for a long time.

It's the same plug, they all looked the same. One with flash on and one with flash off

 

[80t0ylc]

How 'bout your 02 sensors in the cats? Don't they tell the ECM to run rich or not? Posting any codes? Just a thought.

 

[Romer]

How 'bout your 02 sensors in the cats? Don't they tell the ECM to run rich or not? Posting any codes? Just a thought.

I replaced the O2 sensors a year ago. There are no codes. I don't think there is a problem. Just digraded performance after 50K miles with a hotter engine dur to an SC, the plugs got harder to ignite causing less fuel to be burnt, at least thats my guess.

With new plugs all is good.

 

[nakman]

Obviously due to the inferiority of the LX... it's only a matter of days before that thing leaves you stranded.

 

[tblume]

what's the time between replacement for plugs on the crusher? seems like 50K is stretching it.

 

[latinoguy]

How does the plug gap change once it is on the cylinder head?

 

[wxm]

[/INDENT]Everything is running fine with the new plugs, take a while to see if the MPG goes back up. Just thought I would share with some long term data that's much better than seat of the pants info

Hi, Ken,

Just to confirm that the new plugs stopped the unburnt fuel smell. My 96 LX has pretty bad smell too even after a major turn-up last year (I went with the stock plugs not the platinum though. I am wondering whether that would make a difference.)

 

[Romer]

Hi, Ken,

Just to confirm that the new plugs stopped the unburnt fuel smell. My 96 LX has pretty bad smell too even after a major turn-up last year (I went with the stock plugs not the platinum though. I am wondering whether that would make a difference.)

I doubt that would make a difference. Probably something else causing it. I went with the Platinum plugs so they would last longer and due to the extra heat of the SC.

 

[agomez]

check rotor cap wires timing and make sure throttle body has been cleaned....

 

[retrofive]

General question and thought. Years back in my VW's, when installing new ones it was all ways best habit to check the gap and tap into the same tolerance. This may have just been due the fact from the factory the gap never was the same on 4 spark plugs.

Doesn't sound like this is the problem, But I would imagine the same thing goes for Mr. T's plugs?

 

[Tools R Us]

Good looking plugs for that mileage! IIRC the MR2 plugs are different heat range, better matched to the super, that's probably most of the difference.

what's the time between replacement for plugs on the crusher? seems like 50K is stretching it.

30K is the change interval for stock plugs. I also changed them at ~50K and they looked great, noticed little if any change in performance. Went with Iridium spark plugs, they should have no problem running 100K mi.

How does the plug gap change once it is on the cylinder head?

The electrode wears away, look at the pictures, the edges should be square/sharp, erosion has rounded them. The whole surface slowly wears, so the gap widens. There are two main advantages of the "precious metals" type plugs; they wear slower, so maintain a more consistent gap and have a slightly wider heat range, so spark more consistently with changing engine conditions.

 

[gnx7]

what kind of MPG do you get? I'm getting around 12mpg going 70-75mph 80% of the time and 20% in town driving. 33's M/T with stock 4:10's. I can get low/mid 10's if I drive like I stole it in the same conditions.

I'd like to get 14-15mpg . I did the next best thing... bought a '98 VW Jetta TDI and now fill up every 600 miles. It gets high 40mpg. Got it for $3500!