plug check, please

[diy83sc]

Here's the story. I have a stock 83 SC. The engine runs strong, doesn't use much oil (~1 qt 3000 miles), but smokes every once in a while on startup. Not the little puff, but a big blue cloud. I don't understand how it is that sometimes the car can sit for a week and start clean, but sit 30 minutes and blow smoke... but that's another topic.

The plugs look fine except that number 2 and three are a little dark inside. The outsides are are grey. Do these look okay? They are left to right cys 1-3 and were replaced last 3K oil change.

Thanks!

Tony

[jmohn]

Nice pic's, but not like seeing them "in the flesh" so to speak. It may help to know how many miles are on them. If higher miles (around 15K or better), I'd say number one is running a little leaner, if lower miles (less than 8K or so) I'd say numbers 2 and 3 are running a tad rich. The electrodes don't look "cruddy" and the color on the porcelain "appears" to be a fairly normal tan to brownish color, not the soft black of running way too rich nor the greasy black from excessive oil burning. If they were mine, I wouldn't be worried, I'd consider them normal (although, again, it would somewhat depend on how many miles are on them). Just for comparison, I changed mine this spring ('78 SC), had almost 15K on them, they all looked very similar to your number 3, except mine had just a bit less "color" on the porcelain. BTW, mine also uses about a quart between oil changes (3K miles).

Jerry M
'78 SC

[sammyg2]

The first one is lean, the second looks a little rich but not too bad, the third looks to me to be almost right, just a tad on the rich side which is where I like to run them with CIS.
I don't see any signs of oil fouling on any of them so that's a good sign.
Can you see any small silver colored specks on that first one?
with a magnefying glass you can actually get a lot of information from plugs. If you see silver colored specks or dots it can indicate melted aluminium from pre-detonation, that first one looks lean enough to make me a little nervous.
I would also check the injector flow on that first one to make sure it's flowing as much as the others and has a good pattern. Injectors are cheap for CIS (around $21 each last time I bought a set) but fuel distributors are not cheap. Hopefully the problem is in the injector.

I can't tell form the picture but I'm assuming all three plugs have the same heat range.

[stlrj]

All the plugs need to look like the first one. The rest are fouled and need to be replaced.

Cheers,

Joe

[Bones]

I wouldn't say those plugs were fouled?

[Zendalar]

If the plug fires, its working, if its not, its fouled. Plug fouling usually is only temporary and you might not even notice it at times.

Those plugs look very clean, you should see my plugs on my carbed 911T

[diy83sc]

jmohn, they are only 3000 miles old, with mostly highway/DE driving.

sammyg2, I checked with a magnifying glass and did not see any metallic particles. The injectors were ultrasonic cleaned and backflushed with berryman b-12. I rotated them since the last time I changed the plugs to make sure it wasn't the injectors. The plugs are all the same heat range (W5DC.) and looked identical before I replaced them.

I guess what I am getting at is the need to pressure test the system and see if the fuel distributor is the problem or if in fact, the blue puffs of smoke have anything to do with cyls 2 and 3. If that's the case, I am going back to my mechanic who refreshed the top-end when I replaced studs... It's gonna be tough though, unless I can pinpoint the problem.

Zendalar, In fact I do notice some fouling. I can hear the exhaust note broken up at times, mostly when the engine is not at full operating temp but close to it... but not always.

Here are cyls 4-6. Either the fuel is more evenly distributed, or oil is getting past the valves somehow on 2-3.

Thanks for your help!

Tony

[1fastredsc]

I used to race dirt bikes, so i know what f**ked up spark plugs look like. If i were you, your plugs, including the top don't look bad. Only two i'd be even remotely worried are the two that are darker than the rest. It signals that they are either running midly richer than the rest or burning some oil initially then burning away the excess oil off the plug. In the 2cycles i raced, they would always get dark, but when i back up the amount of oil mixed in with the fuel, it would still burn oil (normal function of 2-cycles) but wouldn't be as sooty as it normally would. I did this if i wanted to extend the life of the spark plug a little longer than normal.

[diy83sc]

The problem here is I can't back off on the amount of oil mixed in. For the next 3K, I'm gonna clean these up, richen the mixture a tad, and see what they look like then...

Tony

[911pcars]

It's not as accurate to determine air/fuel mixture by reading plugs anymore. However, your plugs look a little on the lean side; normal for a smogged engine. Use a CO meter to adjust the mixture.

If the plugs were fouled, the engine would misfire. I suspect your engine doesn't misfire. However, the exhaust valve guides might be worn which allows some oil to go out the exhaust. Monitor your oil consumption.

Sherwood Lee
http://members.rennlist.org/911pcars

[diy83sc]

That's exactly what I am trying to narrow down... if the guides are worn or not, and more importantly, why the mechanic did not replace them when the heads were off to replace the broken studs. I had rings, valve seals, and guides on the list. When it came back, only the seals were done and a few guides. They told me that the others measured within spec. Heads on the one bank would have to come off, right? Here we go again

[911pcars]

A puff of smoke on occasional startup is ok. 1 qt/3000 is ok too. Ask a buddy to follow you as you accelerate and decelerate and see if blue smoke results. If not, enjoy your car.

Sherwood