Ok fellas, I need some help. I'll give you the details and see if you have any ideas that I could use diagnosing my 850.
I have a 1993 850 GLT non turbo, manual transmission. I owned it for about 2 years, and it has approx 155000 miles. In the last 2 weeks it has been running very rough. When I say rough my analogy is it feels like I'm running on 3 or 4 cylinders not 5. It actually began a little prior to a couple weeks ago, but it was so subtle I didn't give much thought to it, after it ran for a minute it was fine.
So, about a year ago, I did the whole PCV hose job replacing flame trap, vacuum hoses, intake gasket, whole nine yards. Replaced all spark plugs, wires, distributor cap and rotor and coil. Back in the fall I changed the fuel filter. Last week, changed the distributor cap and rotor as it has some corrosion. Pulled all plugs and they appeared to look fine, not black indicating too rich or too lean either.
I pulled the codes and got a 1-2-1 which is MAF sensor. Took that out, cleaned with MAF cleaner, checked the OHMs ( was 111), cleaned the connections and reinstalled. Code cleared and never came back. Currently no codes, 1-1-1. I have looked at vacuum lines, checked airbox flapper and blocked it open to cold side, no change. Battery voltage is 12.87 off, 14.65 running. I can smell some fuel, when I drive it, but not always.
Could it be clogged injectors, catalytic converter, MAF sensor, or what. I'm stuck and need guidance.I have read and researched alot and I'm at a stand still now! Thanks in advance!

 

Do you smell fuel in the cabin or under the hood? Check your fuel pressure regulator. Pull of the vacuum line after the car has been running, any fuel in there and it is bad.

Is it running rough (like a misfire) at idle, or across the RPM range under load?

 

It runs rough idling and across all rpm range. I'll check the regulator. I smell fuel inside the cabin, have noticed when I've had the hood up and trying to figure out this dilemma while car is running too. It fires/starts right up, just runs rough like a cylinder is dead.

 

Well here a user described a cracked fuel line (i think its an evap line) they had above the gas tank, and how they dropped the tank to access and fix it:

https://volvoforums.com/forum/volvo-...ix-pics-55740/

It could also be the fuel pump seal.

If your plugs look good, and there are no stored trouble codes, then I'd say first priority is finding the fuel smell. It has the potential to cause a bad running condition if it is a cracked hose, not to mention being a serious safety problem, to leak fuel. Even if it does not solve your problem, it needs to be done.

Try unplugging your MAF and seeing how it runs. Sometimes it takes quite a while for a MAF trouble code to set, if it sets at all. They can be bad and not set a code. The face that yours DID set a code means that at some point it went out of range.

 

My guess would be that you have a loose or broken vacuum line somewhere. Look real close at your elbows and replace any that are soft and feel tacky.

I'm a little confused that you replaced the rotor and cap twice within a year or two. That makes on sense to me. A common failure is fuel pumps and fuel pump relays so you can check fuel pressure. If low, replace the relay and pump.

If that doesn't help do a compression test.

 

I unplugged the MAF and ran it around for awhile, no change or difference. I changed the distributor cap and rotor because I had it available to me, brand new on my shelf. I ordered extra for some reason awhile ago. I only did this to eliminate that as a potential problem as the one I took off has a fair amount of carbon tracing on cap and rotor. I'm going to look very closely at the vacuum lines, fuel pressure regulator and some other stuff. I would like to do compression test but need to acquire the tools to do that. The fuel smell is not real strong or always present, but every now and then I catch a whiff. Thanks for your help and ideas.!

 

Well, here is the update. After checking alot of components ( MAF, IAC, fuel pressure reg, etc) and not finding any smoking guns I started the car and strated pulling spark plug wires one at a time. All of them caused the car to almost die immediately except #2 cylinder, no change. I pulled that plug and it looks brand new, actually only 8000 miles on the Volvo OEM plugs! I put a old in in and everything is back to normal and running great!
Thanks to everyone that replied and helped me get this thing figured out. I really appreciate it!

 

The plug appears normal? It must be open internally.

Good diagnosis.