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Reading plugs?


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compcoder
New User

Dec 20, 2013, 6:07 PM

Post #1 of 7 (1078 views)
Reading plugs? Sign In

I'm not understanding this entirely. Is there any merit to trying to read plugs in a modern fuel injected engine? Do the plugs need to be new? Will the arc mark change after each test run of the engine? Can this be done in park, or should I drive the car down the road? What kind of throttle should I use and for how long?

EDIT: I should have been more clear. I'm talking about the timing stripe that is made on the spark plug. I've never seen anyone do it with a modern engine.


(This post was edited by compcoder on Dec 20, 2013, 6:30 PM)


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Dec 20, 2013, 6:34 PM

Post #2 of 7 (1060 views)
Re: Reading plugs? Sign In

I've been doing this for about 50 years and I've never heard of what you're talking about.

There's nothing to time on today's ignitions systems anyway.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



compcoder
New User

Dec 20, 2013, 6:43 PM

Post #3 of 7 (1056 views)
Re: Reading plugs? Sign In

Here is an excerpt from a book, but it is generic:


Link deleted ............. not allowed


(This post was edited by Hammer Time on Dec 21, 2013, 3:27 AM)


Hammer Time
Ultimate Carjunky / Moderator
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Dec 20, 2013, 6:48 PM

Post #4 of 7 (1050 views)
Re: Reading plugs? Sign In

We have always read plugs for what kind of deposits are left on them and how hot they are burning but that timing stripe is a new one on me.

Like I said, nothing is adjustable in ignition timing any more anyway.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



compcoder
New User

Dec 21, 2013, 12:42 AM

Post #5 of 7 (1027 views)
Re: Reading plugs? Sign In

I found this on Honda-Tech. It's a pretty good read. I suppose it's more of a tuning issue (where applicable, non DIS)



Link deleted ............... not allowed

Please read FORUM RULES


(This post was edited by Hammer Time on Dec 21, 2013, 3:26 AM)


Tom Greenleaf
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Dec 21, 2013, 3:12 AM

Post #6 of 7 (1020 views)
Re: Reading plugs? Sign In

? Are we allowing links on this thread?
Plain looking at a spark plug tells of what has gone on in that cylinder. Not conclusive but if you are looking at plugs that you are replacing pay attention to one or more being different than others.


When chasing down a problem they can help both to tell which cylinder and what type of problem - that's as old as the hills. Your view without scopes or any other equipment to tell you what you should do next if anything.


IMO it's always a good idea to note what plugs look like when there and which cylinder each came out of. Say you drop one when new by mistake - mark which one if it instantly doesn't run properly it's probably that one.


Many plain pics on reading plugs. Here's one that may show basics easily found...............



A tad hard to read the script but the basic idea,


T



Discretesignals
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Dec 21, 2013, 8:44 AM

Post #7 of 7 (1000 views)
Re: Reading plugs? Sign In

As an automotive technician looking at the annealing marks and how the plugs are burning is not as near critical as reading them when you have a problem such as the ones Tom pointed out. If you have modified or built an engine that is other than factory design, reading plugs for tuning purposes would be important. Most fuel injected or even carbed factory engines are designed to run with certain plugs and the software that controls the engine's timing and fueling is designed with that plug in mind. That is why it is important to service the plugs with what the manufacture specifies if you want the engine to perform as it was designed.

The only time reading plugs is important for a technician is when there is a problem. Reading plugs along with gathering other information from sensors and datastream pids can help troubleshoot problems. Sure you can read them on a stock factory fuel injected engine, but to make modifications for precision tuning to ignition timing and fuel control requires modifying the factory software. Most repair shops aren't equipped to handle making modifications to software other than reflashing modules with factory software. You would have to look into a shop or individual that specializes in that area, which is not worth the time or money, unless you have made modifications to your engine that exceeded the limits of the PCM's software.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Dec 21, 2013, 8:46 AM)






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