Hey everyone, this is my first time asking for help on this site, so forgive if my questions and problems are spaced out. I am the proud owner of a 1989 Volvo 240 which has been running strong for 2 years, but has been running poorly for the last week. No check engine light and no OBD codes have come up.

Symptoms
-The symptoms are mainly shaking/sputtering of the engine at idle and acceleration and loss of power. It sounds like my car might just stall out when I come to a stop or change rpm. I also noticed the engine oil dipstick and valve cover faintly smell like gasoline. I have been told this could be because of a sticking piston ring or a plugged up crankcase ventilation system. I somewhat doubt this because the oil separator/breather was replaced and the rest of the pcv system and flame trap were cleaned about 10 months ago. I have also used seafoam in the oil, fuel, and vacuum line leading to the intake before every oil change (about every 3 months).

What I have done so far.
-Since my check engine light doesn't work, I checked the OBD-I port sockets 2 and 6, with engine off and key in run position, for any logged codes and came up with 1-1-1 on both twice (so no faults). Adjusted the throttle linkage correctly. Cleaned out the throttle body, which was filthy, I noticed that the intake manifold appeared wet. I believe this is because of a leaking fuel pressure regulator. I have also cleaned the MAF with MAF cleaner in hopes it would help. I have also listed the parts below I have ordered and will be replacing this weekend.
-new fuel injectors
-new fuel pressure regulator
-new fuel pump relay
-new distributor cap and rotor
-new spark plugs and wires
-new engine oil and filter

What I suspect
-insufficent spark or no spark
-running rich
-fuel pressure regulator leaking gas into intake manifold
-leaking fuel injectors
-faulty fuel pump relay

The car will turn over and start, but I am reluctant to do so in fear of igniting fuel vapors in the oil. Although I would imagine that the flame trap would keep this from happening.
What is the safest way to change the oil and filter in light of this? Should I bite the bullet and try warming up the engine before the change, or try draining the oil with engine cold (it's like 30 degrees F out here by the way) which will take awhile and might not get all of the oil out? Why is my car not throwing any codes if it is running this poorly? Also do you think I am on the right track for fixing these issues?

Sorry for the long thread. Please let me know if you need more information to go on and I would welcome any advice to my problems. I will update this thread as I find out more.

 

I'm not going to be of much help but....

What is your exhaust like? Smell like fuel? Blacksmoke? Cardinal signs of running rich. But yeah, I would change out the leaky fuel pressure regulator before cranking it up. That's just me - I hate engine compartment fires.
And any time a car runs rough I like to replace ignition components unless pretty new. Even if they aren't the cause, they are quick, cheap, and you will have eliminated a potential problem.
Lastly I do the relay and injectors, mainly because I suspect them least.
I guess a leaky head gasket should be suspect too at the end of all this. In my experience though if an engine hasn't been badly mistreated they don't just roll over and start leaking all of a sudden.

That seems like way to frequent use of Seafoam IMO. If you are building carbon up that quickly there are big problems and cleaning the crankcase that often is just flat overkill. No problem with running a fuel system cleaner through it every 3k miles though.
If Seafoam will clean out the carbon it should have done so by now - personally, I would run some RXP or Techron through it every 3 or 4 tankfuls.
I also run a bit of Marvel Mystery Oil for a few hundred miles before oil changes to keep things clean. And use synthetic.

 

Dylan , it sounds like you are on the right track with the ignition parts. After those are in, and the problem is not solved, I suggest reposting in the 240/740/940 section that is a little farther down on the index page. The folks that really know these cars hang out there and can give you expert advice.

 

Update

I replaced all the parts listed above and I noticed that the gap on the old spark plugs were around .040" instead of the recommended gap of .028-.032". The spark plugs also appeared to be fouled. Next the old rotor cap had lots of carbon build up on the contacts and one of the spark plug wire contacts was extremely corroded. Now that I have driven the car around for a few days, I can confirm that I have fixed the issue.
In hindsight throwing money and parts at the problem was not the best approach, but in the end the problem was solved. Thank you everyone for the replies and advice.