Trouble Starting, Uncontrolled High Revving

[santem]

I had the same oil leakning and a problem starting on my 2000 S70 which sat for 3 months. Turns out that the oil can find its way down from the cap into the coil and the spark plug housings. I would reccomend replacing the spark plugs, especially if you notice oil on them and the gasket to the oil cap because once it gets oil on it it becomes basically useless at preventing other leaks. Try giving the coil housing and the housing of the sparkplug a good cleaning. The guy at my dealership warned me that the oil can also get into the flame trap (Im not familiar with 850's so i dont know if the design is exactly the same)
Be careful because the oil also causes the black wiring housing for the spark plug wires on top of the engine block to become brittle and basically disintigrate.
Don't know if this was suggested but It also wouldn't hurt to clean your Mass Airflow sensor and see if it helps.
Hope this helps

[jblackburn]

Ah, you were talking about the idle control valve.

I would suggest removing that from the car entirely (you'll need 2 new clamps from an auto parts store) and cleaning it thoroughly with carb cleaner. It may help smooth out your idle, but hopefully the coolant temp sensor did a lot of good too.

Can you shoot a video with a phone or something of how the car's idling at the moment?

[TheWhiteBrick]

Thanks for the tip, that is a possibility. I planned on doing a compression test on the engine to get an idea of what's going on also, I can check out the spark plugs then. The strange thing is I got it starting and running no problem, then randomly after driving it several times with no symptoms whatsoever, I come out of a restaurant last night only to have it not start. It took several attempts, then it finally started and ran terribly, then since it had helped before, I unplugged the connector I had thought was the TPS, but was actually the idle control valve, and plugged it back in, which seemed to fix it. Could my problem be a malfunctioning idle control valve?

I should also add that the temp gauge has been going all over the place. It has been sitting about 40% while driving, but sometimes will be non-responsive entirely. When I had problems getting the car to start last night, after it finally did start, the temp gauge would be all the way at the bottom, then would jump up intermittently. Am I having a ECS and idle control valve problem?
Thanks everyone for the input, I feel like I'm really close to a solution here, and my car will be all the better from all the great knowledge on here.

[jblackburn]

This car is desperate for attention, but it sounds like it may need it.

1) Change the coolant temp sensor (most call it an ECT actually). With it jumping around, that thing's bad, no question about it. That's causing your starting problems, because the engine has no idea how much fuel to inject to get the thing started. Cold engines require a lot more fuel, and it may choke if it does that on a hot engine (ever tried starting a hot lawnmower with the choke setting on, or a cold one without it on?)

2) You may have a problem with the idle control valve, but USUALLY it's just dirty and the flaps inside stick. Clean the throttle body too, it may be sticking.

3) Seafoam won't keep you from having to replace the PCV system. Rather, I'd replace that first, and THEN seafoam the car.

[TheWhiteBrick]

Looking at FCPEuro.com's PCV kit, you mentioned in your write up that its better to get the genuine volvo parts rather than the URO replacements, but if I take the same item number from the kit which is supposed to be for my year car and do a search for the Volvo counterpart, it says it doesn't fit my car, can you shed some light on which parts I should swap out for the genuine Volvo ones? I am going to order parts today, and get all this done asap.

[jblackburn]

Best thing to do would be to call them and ask that they match the part numbers to the kit for your car. They DO NOT show (last I looked, anyway) all of them on the web site as OEM parts.

1994's are tricky, as they have different PCV parts than all the rest of the ones after them.

[TheWhiteBrick]

Alright guys, here is an update, I think I am headed in the right direction, but still having problems.
Changed the ECT sensor, did the swap on the PCV system (thanks to jblackburn for the writeup), everything went great. The car now runs great, pulls strong, sounds good, but my problem is still getting it started.

If the engine is cold, it starts up every time, no problem. If I start it and drive down the street, once the engine is shut off, it will not start. I either have to try and try, or wait for it to cool down. Sometimes when it does start, it runs really choppily, and at very low rpms, with a bottom-of-the-line temp reading. Then, after about a minute, the temp sensor goes up to about half way, the engine smoothes out, everything is fine. I cleared the codes from the engine after the work I did, but directly after clearing them still got a 1-2-3 code. Do I have to clear the codes once for each code? Why am I getting a 1-2-3 with a brand new sensor?

What seems to be happening to my very unprofessional eye is that faulty temp sensor signal says engine is ice cold, it tries to start very rich, the engine is warm, and will not start. If it does start, the computer decides the sensor is not working and adopts a middle value, the engine runs fine.

Let me know if you have any ideas...
thanks!

[jblackburn]

I believe that is what's happening and it's choking the engine as if you left the choke on on a warmed-up carbureted engine. What brand sensor did you replace yours with?

Did you clean the connector very well to it?

If it's an OEM sensor, then I'd try to grab some resistance readings from the sensor itself. A hot engine should show between 300-150 ohms; a cold engine something around 5000.

[TheWhiteBrick]

Would I just unplug the sensor and put the multimeter probes in to the plug?
I just cleared the codes from the engine, but the 123 code seems so be sticking around, although I did just start the car a couple times in a row after clearing codes and it started fine, but it didn't really get a chance to warm up too much.

[jblackburn]

Yeah...readings at the plug will tell you what you need to know. Make sure there is no corrosion on the engine side of the plug.