How soon does it make sense to read new spark plugs?

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moribundman

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How many miles should I put on new spark plugs until I pull one and check whether or not the heat range is apropriate?
 
Two cycle? If it is a two cycle you can check them after a long wide open run, say 3 miles, Shut the engine off and coast with the clutch in until your stopped. 4 cycle I would check after 500 miles, but hard to tell if you idle alot.
 
I put a different type of plug in my Audi just recently. It's a plug with a dual heat range and I just want to make sure the plug is not to cold. I guess I can chck already, because I've already put over 1000 miles on it.
 
All are sparkies are easily accessible. The only issue I have with pulling all has to do with the plugs having a crush washer. And this particular engine tends to rattle plugs loose, especially if a plug is reused. I understand you point and agree, but I have to say that so far, all 6 plugs have always looked practically identical, so I hope to get away with checking one. Maybe I'll pull two...
 
Checking your plug insulator color is valid, but realize that cruising/light throttle will show different results than full throttle.
You may want to check them after driving normally, then check them after a full power blast [ shut down and check immediately].
 
I'm not talking about checking only the insulator. I want to see if there's any carbon build-up on the electrodes.
I drive my car usually fairly hard, but I won't pull over on the highway, pull my plugs, then wait a few hours for the engine to cool down before putting the plugs back in.
The OEM spark plugs are NGK BKUR6ET-10. I believe they have a heat index of 6. The Beru Ultra-X UXF5.6 spark plugs that I'm using now have a dual rating of 5 and 6.
 
Pitbull, the NGKs performed always very well. I simply wanted to try the Beru plugs, because they came highly recommended by another Audi A4 owner, who does know a lot about this particular 2.8 engine. The motor runs great with them, but I found out that Audi recommended the Beru Ultra-X UXF7.9 in this engine. That plug has a heat index from 7 to 9! My Audi compadre told me the UXF5.6 is teh favopred plug by tuners, and thos epugs look perfect in his motor. What he failed to mention was that his engine is modded and makes 50 horses than my 174 hp motor. I'm not aware of any Beru plug that covers the heat rnage form 6 to 7.

From what people have said, I guess, even driving only a short distance can severly influence the look of the spark plugs?
 
There is no other way to get a valid reading of a spark plug under load than by 'cutting clean', after a full power run. Once you drive at normal throttle/light loads, the results are meaningless [except for those lightly stressed conditions].
Yes, it is a pain in the derrier.
 
A 'practical matters' question for anyone: Most all engines have aluminum heads nowadays-will pulling and/or replacing the plugs on a full-hot engine tend to rip the threads out?
dunno.gif
I had to helicoil my two-stroke heads years ago after multiple plug readings.
 
Those two stroke heads probably had short reach spark plugs - not hard to strip threads! They also have a lot of carbon that abrades threads when removing the plugs. Most cars that have aluminum heads have long reach threads, and are much better in this respect. We like to remove them when warm - the head is expanded a little and lets up pressure on the plug threads. The problems we run into are seized plugs that cause damage on removal, but it's pretty rare.
Plug readings are different now. There are additives in the fuel that color the insulator, and they seem to take a long time to get any color. If your engine is way lean or rich, you can tell, however.
 
Let's try again, becauxce I'm afraid one tidbit of information has been overlooked:

I said I put COLDER plugs than recommended in the engine. My concern is not that the plugs won't perform well under load, but when cruising around town witout the engine getting really hot. Wouldn't it make senseto check the plugs after an hour of lame driving?

Audi's recommendation for plugs are NGK BKUR6ET, which I believe to have a heat index number of 6.

The plugs I am using now are Beru ULTRA-X 5.6, which have a dual heat index of 5 and 6. The next step up is the Beru ULTRA-X 7.9, with a heat index of 7-9. Beru lists the 7.9 version as the correct one for my motor, but other Audi owners prefer the 5.6, as it usually looks near perfect.

A hotter plug results in lower emissions, I believe? Maybe that's why Beru recommends the hotter plugs?
 
Mori. Remember that heat indexes for various plug manufactures are not always equal. And, remember that NGK's scale works backwards. The higher the number the colder the plug. Do you know which way the Beru Ultra-X plug scale works?
 
Hey HEV, I was aware that the heat index numbers might differ between brands, but I did not know that the scale might be reversed! I'll have to check into that. Yikes!
 
Yeah, I've come across this before. Looks indeed like the NGK scale is backwards, with 2 being at the hot and 11 at the cold end.
I can't find a comparison chart between different manufacturers, but it seems Bosch plugs go from 06 (cold) to 13 (hot). Couldn't they find a convenient standard?
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How the vehicle runs is your first clue. If it missfires when accelerating after driving moderately for a while, but runs OK when driven hard, you're probably running too cold a plug.
 
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