One of my Volvos is giving me real grief right now, and I'd appreciate some advice. It started to misfire on the freeway last weekend and is throwing code 301 plus my sensor is flashing the following icons: EV OH C O.
I have replaced the #1 coil and the plug to no avail. As a further step in trying to diagnose this problem I am considering starting the engine with the #1 coil unplugged to see if I can detect power going to the plug in, and then doing the same with #2 for comparison. Might doing so damage ECU? Does anyone have any other suggestion? I am also considering interchanging the injectors to see if that moves the problem around, as well as a compression test.
Thanks,

Thanks for getting back Klaus. I had planned to pull the electrical plug out of the coil and then check the current coming out of the electrical plug with a wire tester while the engine is running. That may not be a good idea though? The sparkplug, by the way, is wet and black and must be getting fuel for sure. I will do that compression test as you suggest. The miss on #1 arose suddenly on the freeway while running at highway speed under full load, pulling a bike trailer, so I don't know if it is electrical or maybe a valve?
Thanks again

firing the engine with the coil removed from the plug will destroy the coil. Do not do that.
Did you check the spark plug gap?

Moving the injector is not that easy, and if the spark plug is wet or black it is working.

Moving the new coil to # 2 would be a good test. If you can, get a compression test.

Klaus
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Mistakes make us learn. Beer is for a job well done.

Still doing more investigation to try and figure out what could be causing this misfire. Could it be the crank position sensor acting up?
Thanks

I am still trying to solve this misfire on #1 issue and would greatly appreciate any advice or information. Thanks in advance!
I have run the engine with the 'plug in' for the coil unplugged but leaving the #1 coil and spark plug in place though unplugged from the car's power. This should protect the coil from being damaged. There are three wires going into that 'plug in'. The black ground wire is grounding properly, the red wire is under power without interruption, but the smaller yellow and black wire is dead. Should this wire be under intermittent power to determine the firing of the spark plug? If so, then I've likely got a break somewhere?? Also does anyone know the ohm (?) level of this wire and whether it would be sufficient to light up a regular circuit tester? Maybe there is power there, but insufficient for a circuit tester to read??
Thanks alot

Well I went back at this again today. I held a plug tool that has a tiny sensor light built into it next to the coils with the engine running. All the coils produce the same read out, so I am concluding the problem with #1 is not electrical. The #1 plug is wet and black, so I am thinking it might be an injector stuck open that's causing the misfire. Any opinions? I'll search the BB for any guidance about removing the fuel rail etc.
Thanks

So will a sticky/dirty valve. Getting a compression test will tell you a lot, but the cylinder will need to have a table spoon of oil added to it first. All of that gasoline has washed the oil off the rings and you will be lucky to have 50lbs of pressure. A stuck valve will show 0 pressure.

A stuck fuel injector is quite rare.

Klaus
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Proud owner of a 1967 220S

Thanks Klaus, excellent advice. I'm learning a few things here. My own reading just now about injectors tells me they can get gummed up and then stop flowing. I will get hold of a compression tester and go that route.
Thanks again

Did the compression test, both dry and wet. Zero compression on #1. I have taken the car to my local independent Volvo repair shop. One of the exhaust valves is burned. This is my third Volvo with this 5 cylinder engine, I don't know what could have happened to this one....