Spark plug look (THP) - are they all right?

[tomu80]

Hi!

Because of bad LTFT after timing set replace (it keeps decreasing and now it's at -6,2 %) I decided to check spark plugs condition. I think that they don't look as they should (outer electrode colour turned to red):





I've done on them 30 kkm. Along with timing set replace I've upgraded intercooler recently with larger AIRTEC FIMC. i don;t know if it's important.

Now what does that red color on the outer electrode means and what about some black deposits on the insulator? Is it ok or is it running too lean because of perhaps bad timing setting (that LTFT at "-") or maybe it's a plug wear? Electrode gap haven't increased - it's still 0,65 mm.

[Soran]

I'm no expert but that inner electrode is shot to bits. It should be as thick as the base of the electrode. Looks like the poor timing caused it according to this:

http://www.verrill.com/moto/sellingg...colorchart.htm

Yours looks the same as the 2nd one down left hand side.

[Jamie@SPTuning]

The electrodes look like this new, they have not eroded away. Looks like they seen better days though.

[tomu80]

Jamie - and what do you think about that red electrode colour and dark spots on the insulator? Is it ok? Arent they too hot or maybe it's a sign of some detonation going on?

[Soran]

The electrodes look like this new, they have not eroded away. Looks like they seen better days though.

Shows how long it's been since I played with Spark plugs then Jamie. Think it was on my Mk3 Escort! :eek:

[Jamie@SPTuning]

Have you had terraclean?

[tomu80]

Have you had terraclean?

And what is it exactly? I havent been using any fuel additives.Recently (since about a month) I run on BP Ultimate 98. Earlier i was runing on a normal 98 (not from BP). LTFT is at -5,5% which means that ECU is trying to lean the mixture - question is why? I understand that ECU "thinks" that mixture is to rich, but why? The ony 2 things that has been changed lately are: bigger front AIRTEC intercooler, and timing chain/tensioner replace.