IainM

Hi Guys,
Just replacing my plugs after 40,000 miles (I know shoulda done it two oil changes ago)
But they look kinda white to me. Last time I changed them they were more tan in color which was the usual color
from previous cars including the 993 5 years ago.
What do you think? Is this normal or should I be looking for an intake leak or something?


just removed

IainM

found the last plugs I removed from 5 yrs ago:



last change 5yrs ago

IainM

The gap on the top set that I just removed was quite large about 0.86mm vs the 0.8mm spec. Could oversize spark plug gap cause lean running / white tips?

pp000830

I am not sure observing the plugs is a valid measure of an out of specification lean condition. Wouldn't the oxygen sensor trigger a code if such a condition truly existed?
The below URL seems to suggest your used plugs exhibit "Normal" conditions of ignition:
11 Things Your Spark Plugs Are Telling You

Churchill

Those plugs look good to me. If they're consistent then you don't have a vacuum leak at an injector block or manifold. For peace of mind you can always use a sniffer to see your CO reading. A local shop would probably charge you $20 to use it.

Steve Weiner-Rennsport Systems

Check those AFR's.

Reading plugs requires a very specific procedure called a "Plug cut" (and a LOT of experience) to get any kind of accurate picture of what you have. Just pulling them out of an engine thats been idling tells you nothing besides idle fuel mixture.

A good chassis dyno run will show AFR's so you can see if they are within a good range.

IainM

Just got the top 6 out and they are all consistent. These were the lightest grey I have seen in 40years or car maintenance - having said that, my 993 is the most efficient and clean burning car I've ever had. Thanks for feedback. never stop learning.

On a tangent, I notice the new Bosch plugs going in are from China. Whats the early data on reliability/quality? Should I replace these in 15k miles?

pp000830

I hate to say it but this thread follows a common Rennlist 993 thread pattern:

1. The original poster did something that was most likely unnecessary (removed his unworn plugs);
2. Made a posting here expressed a concern for a non-existent problem (worn plugs/fouled plugs);
3. Members chime in with comments about a similar experience;
4. One or more members suggests that a problem doesn't exist and in some cases provides examples from athoritative sources through google searches;
5. A knowledgeable professional 993 servicing member of the community doesn't disagree with the conclusion that there is no problem but suggests one could do a definitive diagnostic procedure to confirm there is no problem by spending a large sum of money on what is most likely an unnecessary diagnostic process (dyno).

Proof that if you look for love in the wrong places hard enough you will eventually find it and she will be a very high maintenance girl (993) who seems to constantly want to go on expensive dates (servicing events) where your relationship would be better if you went on fewer dates and occasionally took her for a ride in the country.

Railmaster.

You nailed it! I will never do a leak down test ln my car as long as I am satisfied with the way the engine runs!...

IainM

Andy, relax. I'm not dropping the engine to do a full top end rebuild. The plugs had 40k on them, Porsche recommends changing at 30k. I pulled them out, the gap was out of spec so I think I have done a good thing in replacing them. For the price I surely ain't gonna regap 36 electrodes!!!
My request was for discussion on an observation of the plug tips I'd never seen before, that light white color and I was reassured by several, you included, that it was normal.
I'm looking forward to enjoying a few extra restored ponies on my next drive.
I'd say this is exactly what Rennlist is about.

But if you'd like me to tell you about the leakdown I did, that'd be for another thread.

pp000830

Thank you for the thoughtful reply. For the record I replaced my plugs at 80k miles and will probably consider it again at 160k miles if other work is needed at that time. In the old days when plugs ran at a lot less than 10k volts gap was a big deal for proper function. I feel at the extremely high voltages used on our cars if a reasonable gap is present it will fire even if out of spec. and if not an O B D misfire code will present. Reading my original posting, I have to apologise for its possibly snarky tone, no insult intended.