fouled spark plugs / oil on intake valves

mike944 · 06-30-2002, 04:54 PM

Hi guys,

I was in the process of replacing my heater valve, because my heat has been stuck on. I removed the intake manifold, because it seemed like the easiest way to get at the heater valve. When i did, i noticed oil puddles behind the valves that were closed. I pulled the spark plugs (Bosch platnium +4's) and they had alot of crap on the 4 ground electrodes. the center electrode was normal colored.

I know the oil on the valves is probably not from bad valve stem seals, since i just replaced those less than 10K miles ago with teflon valve stem seals. The intake manifold runners have some oil residue inside them, and the intake gaskets had oil on them. The valve stem seals are below the intake, so i believe the oil is coming from the intake somewhere. there are alot of hoses connected to the intake, could any of those be seeping oil into the intake manifold? does the 944 have some type of PCV valve that might need to be replaced? if so, where is it? any ideas?

I'm surprised, because it has been running very good, and it passed our state emissions test less than 3K-5K miles ago with numbers clean enough for a model year 2000 car.

thanks,

Mike

Scott R · Scott R's Garage

Is it a 944 or 951?

mike944 · 06-30-2002, 05:11 PM

Sorry,

'84 944

AFJuvat · 06-30-2002, 07:42 PM

I had good luck getting the carbon off of my Platinum 4's by opening the gap slightly. For this reason, I switched to standard Bosch platinums and left the gap as it was when they came out of the box (slightly more open than spec) In my opinion, the 4's don't burn as efficiently and provide no significant benefit over any other quality plug.

If your plugs are fouled with oil, that could point to other problems, like ring failure.

By what you describe, I am tending to think it is your valve seals. I can't think of anything else it could be (short of a cracked head). There have been reports that teflon seals do not work well with the stock valve guides. While I can't confirm nor deny this, I can say that I have always had good luck with the factory seals.

There are no oil lines running to or in the intake manifold, those are all vacuum lines. The 944 has no PCV valve.

AFJuvat

mike944 · 07:09 AM

the plugs don't look like they are fouled with wet oil, they have some type of hard, crusty residue on the outer electrodes that can be chipped off. is this burnt oil residue? I don't even know if these two problems are related, they seem like they could be.

Damn, valve stem seals are a pain in the ass to replace. I guess i'll finally have to break down and buy a 9201 belt tool.

I was hoping it wasn't valve stem seals. I wish i'd known the teflon seals were not good with stock guides, because I do have stock valve guides, and they are pretty well worn, but they're still well within factory specified clearances (which are amazingly large). I even paid extra for the teflon seals. I'll probably make the seal change a project for next winter.

I'm still looking for potential oil leaks from the vacuum hoses, since my intake manifold gaskets had oil on them, and they're above the valve stem seals. Plus, i've seen oily residue on some of the larger hoses last time the intake was off, but i figured it was nothing to worry about, but maybe it is.

Mike

Makis · 07-01-2002, 10:31 AM

Mike, just clarify to me.
Were all your spark plugs fouled with oil?
Do you have blue smoke at start up or while running?
What is your oil consumption?

mike944 · 07-01-2002, 11:58 AM

Yes, they are all fouled. the front one was the worst, and the rest were a little better.

I haven't noticed any blue smoke, startup or while running, ever since i changed the valve stem seals the first time.

my oil consumption is also minimal, which is why i haven't noticed any problem, until i happened to pull the intake and the plugs.

Makis · 07-01-2002, 12:26 PM

Well it is possible the oil to get its way to the inlet through the breather pipes but common sense tells me the only way the oil to land in the inlet is if the breather pipe path to the inlet is going down. I would check all of the breather pipes that follow this rule. If there aren't I would say the inlet valves are leaking. If the valve seals are the problem then you also should have oil in the exhaust valves, how does the exhaust look like, does it look oily?
From what you saying it seems that the seals work OK when the engine is running and you only have oil leak when the engine is cold when the oil from the cylinder head finds its way down the valve steam into the inlet.

Scott R · Scott R's Garage

If this is the second time in you might want to get some head work done. The cost is worth it and you can get a rebuild with a angle grind, and polish with warranty from several vendors. My old Supercharged NA had this issue. I replaced the guide seals, but the guides were worn and there was still leak-by when it would sit for a day. Reworked head with x-rays and angle grind solved the problem.

Taz's Master · 07-03-2002, 04:10 PM

AFJuvat, when you say there is no PCV, does this mean that the 944 does not vent its crankcase into its intake path? I cleaned my throttlebody and it was pretty dirty. I assumed that most of the gunk I removed came from the crankcase via a PCV. Does the 944 vent to atmosphere (or a charcoal canister), not vent the crankcase at all, or vent to the intake path using a method that does not necessitate a PCV valve?

AFJuvat · 07-04-2002, 09:27 PM

Whoa, a deep in the weeds question.

To be honest, I cannot answer that question. In truth, I've never thought of it. There is no PCV valve. There is however, and evaporative emmissions (charcoal) canister for the fuel system - it may or may not take care of crank case gasses as well.

AFJuvat.

mike944 · 07-06-2002, 07:04 PM

Taz-
while reassembling my car, i found what appears to be a PCV valve. It is NOT a mechanical valve like on most cars, but is an electrical solenoid valve. I was tracing hoses looking for a potential path for oil into the intake manifold. I found one hose that appears to come from the plastic oil filler/resevoir thingy (i have no idea what to call it) to this electrical solenoid valve, and then it goes into the intake, in a port just under, and downstream of the throttle body. This system appears to be some sort of crankcase ventilation system that is electrically controlled. if anybody can confirm or deny this, i'd love to hear it. The solenoid i'm reffering to is attached to the back of the air cleaner housing with 2 10mm head bolts, upside down.

An update for everyone else - i haven't found the source of the leak, i guess it is valve stem seals. I guess maybe the teflon seals really don't work very good with stock guides. the car WAS sitting for maybe a week since it was last started before i pulled off the intake, maybe a small amount of oil after this length of time is normal?

BTW, i found one of those "how to read spark plugs" charts. the deposits i had on my plugs do NOT appear to be oil deposits, they appear to be "ash deposits" the chart says these are from fuel or oil additives. they do reccomend valve stem seals as a possibility though.

Mike

maachan · 07-06-2002, 07:32 PM

If the engine was running fine I wouldn't worry too much and drive on. Time and cost of finding the cause would be too great and what you will get is plugs not fouling. I will have extra set of those on board if I were you. That is if everything else on the engine is working order.

Maachan

maachan · 07-06-2002, 07:39 PM

Oh, I was going to mention about the +4s.
I changed plugs from regular Bosch platinum to +4 today. What a diff. The engine feels a lot stronger now. I don't know why I didn't change sooner. Oh, I know. It's the price. Way too much!!!

Maachan