What is this spark plug saying?

#1

I pulled my plugs today to see how they looked and all of them looked like this picture. I intalled them new in March and the car has been driven maybe 1000 miles since then. Any clues as to why the look so bad?

Also, I swapped out my fuel injectors with a set of used, reconditioned oem injectors and the car now stumbles like one of the injectors might be bad. I haven’t had time to trouble shoot yet but was wondering where you geys would recommend to start searching for the problem. Hopefully its something obvious like a look connection.

sparkplug.jpg509x680

#2

Ken, you are getting oil in the combustion chamber. Either via valve seals or it is getting past the rings. How did your compression test turn out…

check to make sure the connectors on the injectors are all "clicked"on…I had a loose one once and it gave me all sorts of trouble till I finally decided to check the easy part…

#3

Yep, oil. The rule of thumb is, if you can have someone follow you, smoke on decelleration is usually valve seals or guides, smoke on heavy acceleration is worn rings. You may not be able to duplicate these in the shop without a load on the car.

#4

Sean,

I checked my compression tonight and this is what I have. Keep in mind that this is not an expensive professional gauge. I bought it for $30 from Advance.

#1 160
#2 170
#3 160
#4 150
#5 170
#6 165

cylinder #4 took 3 tries to get up to 150psi. I kept reconnecting the gauge and had to turn the ingition for 20 seconds at a time for several tries and the compression slowly came up.

I found the problem with the injectors. The injector on #5 was bad so I cleaned up one of my old injectors and reinstalled it. Runs fine now.

While a was working on the car I noticed that the valve cover gasket was completely outside of the cover across the inboard side for about a 3 inch length. Since a had a spare gasket I decided to change it and check my valves for adjustment. While I rotated the crank I could hear air hissing from around the valves stems. Is this normal? Maybe this is where the oil is going and why my spark plugs look so bad.

#5

No direct exp w/ E30s, but hissing at the stem isn’t normal (where is the compression coming from? The guide/seal shouln’t see any). Turn the crank until the rocker arm lifts the valve slightly off its seat. Use a screwdriver and try to press the valve stem tip back and forth under the rocker. It is moves side to side at all, then the guide is worn. Not the end of the world if not TOO bad. The guide is the only thing cooling the valve, and really worn guides will cause the stem to overheat and snap. Just a little wear and sucking in a little oil can be fixed by replacing the seal.

SMD

#6

You are doing this while the throttle plate is held wide open?
Squirt about a tablespoon full of oil into the #5 spark plug hole then try the test again. If the compression stays low, the valves are the culprit.(my guess)
If it comes right up to spec, then rings

#7

Sean - this is kind of a side issue, but what is the normal compression? I just did mind and they were all 180 - 185, although the car has not been driven much in the last year. Could be excessive carbon build up in the combusion chambers?

Also, did you meann #4 for Ken’s car. Could a bent value or bad seat seal also cause compression loss?

Thanks, Ed

#8

Well as it turns out the 3" gap where the valve cover gasket was supposed to be might have been the cause of all my car issues. I just spent the day at CMP for an open track day and after more than 60 laps I didn’t burn any oil. No more clouds of blue smoke on start-up, no more puffs of blue smoke at high rev shifts, and the car seems to run smoother in general. I have not yet pulled the plugs to see if they look normal but I suspect they will.

I managed a 1:59.5 today which happened to be on my 5th lap of the day (after a warm up session). My times were consistant low 2:00.x until later in the day as they started to creep up. My tires started to loose traction and my brakes began to fade a little. All in all I’m very pleased with my day and the car handled perfectly.

#9

edavidson wrote:

[quote]Sean - this is kind of a side issue, but what is the normal compression? I just did mind and they were all 180 - 185, although the car has not been driven much in the last year. Could be excessive carbon build up in the combusion chambers?

Also, did you meann #4 for Ken’s car. Could a bent value or bad seat seal also cause compression loss?

Thanks, Ed[/quote] Yes, I meant #4…:blush: I think the spec is 175 psi but someone should check bentley for me to be sure.if the head was milled for a HG, the compression will have gone up if the thicker gasket was not used