This is a 1998 c70 hardtop with the 2.3L turbo engine ~225k miles.

I gave the engine a pre-emptive tune up back in March. I bought the full Volvo kit from FCP including new air filter, spark plugs, wires, cap, and rotor. I gave it an oil change and put in a magnetic oil plug for good measure.

Gradually since March, I've started getting CELs. Initially it was a misfire on #2, which would later clear up. I checked the sparks and wires and boots to be sure nothing was loose, but it never solved the issue permanently. The problem had gradually gotten worse, with CELs showing up much more frequently with misfires on #2, then #3, and now #5, plus the random misfire code.

I pulled my cap and checked it for trouble. Rotor was very secure, nothing funny inside the cap. A bare trace of oil around the edge, but nothing obviously wrong.

What's really odd is that the engine is running just fine. I get no detectable feeling of misfire at all, yet I can't seem to avoid the CEL for more than a day or two. When they do clear themselves out, I can see them pending on my scanner tool. Seems to be inescapable, and I've no idea what to do - aside from dropping another $160 on a new tune up kit and hope that I manage fix it.

Any ideas? This is starting to drive me a bit crazy.

There should never be any oil inside the cap, none, zip, nada. A leaking seal perhaps?
Does the misfire go away after cleaning out the cap?

You need to get a compression check done. Make sure the engine oil is warm when you do it.

Have you ever cleaned the PCT nipple? That can cause higher than normal crankcase pressure. Usually, it is the rear cam seal that blows out.


Klaus
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1967 220 belonging to C.A. lives on

Well, the engine leaks oil. it seeps a lot of places but not very much. I have to add a quart every couple months. If the weather were more benign and I had more time, I'd like to pull and replace all the gaskets.

The oil at the cap was a bare film around the sealing surface. There was none in the cap as far as I could tell, but I did clean the edge and reinstall the cap tightly.

I presume that you suspect that oil is getting into the cap and causing the random mis-fires?

I pulled the negative battery cable - I was inside the car replacing my firewall heater hose junction, and took the car on a short jaunt. The codes are currently clear, but it may take a day or two to show up (if it is coming back).

I'll keep an eye on it.

Is this PCT the same as the flame trap? The 98 c70 isn't supposed to have a flame trap, so no. I've not cleaned it. If I have a PCT, where would it be located?


Oil in the distributor aside, are there other obvious reasons I could be getting random misfire codes?

From an old post (not mine):

PTC Nipple.
Positive Tempature Coeficient Nipple.

It heats the air returning from the PCV system as it enters the intake system to prevent any moisture from condensing in the intake system.

Also, when you order the cold air intake pipe from the filter to the turbo, the ptc nipple comes with it. I paid $130 CDN for the assembly in Toronto Canada.


No, you do not have a flame trap, none of the turbos had one. The PTC is on the air intake pipe that goes from the filter bos to the turbo. It has an electrical connection. The only way to clean it is to remove the intake tube and scrape the calcified material out, using a very small screwdriver and throttle body cleaner.

Klaus
--
1967 220 belonging to C.A. lives on

I checked the diagrams over at FCP. Looks like I pulled and cleaned that part back when I replaced my heater hoses.

I *do* know that I snapped the hard plastic breather tube while working down there, but I did macgyver it. Looks like I probably need to drop a couple hundred and replace most of the breather junk down there anyway.

On the positive side, I haven't had a misfire code since I pulled and cleaned the cap.

I'm still struggling with the coolant issue...