Had an odd issue here recently. I've been driving the car with pretty much no problems whatsoever(besides a random hard start issue hot or cold) til yesterday after filling up and getting to about 60 mph I started to get a flashing check engine light. It never stayed just would flash a few times then go away, then come back and flash again and go away again. The car ran like nothing was wrong the entire time, but I parked it as soon as I got home and haven't touched it since even though the light went off when I did. I ran codes only to find one pending code, P0300 for random misfire, and the light doesn't come on at all when I sit at idle. I recently replaced a crank sensor after having a code for it and for my catalyst below threshold, neither are still present (and it helped a little with the hard start issue) So any ideas? I'm thinking a tune up and inspecting coils, but all advice is welcome!

 

It might be time for some spark plugs (get factory ones) and possible a coil or 2. Usually the MIL will indicate which cylinder is acting up

 

That's what I figured have new factory plugs and coil on the way from FCP, hoping to pull it apart later after work. Not sure why it wouldn't give me a definite cylinder but I'll be checking for cracks in the coils hopefully
i can pin point it.

 

I agree, it could be plugs, and it could be a bad coil. But it could be a bad ground, a bad battery, an alternator on the way out as well. Just don't think it is going to be just one thing--it is a system with multiple subsystems that is getting older.

I suggest you always start with the basics. Plugs are a given. Look for problems while there, of course--oil on plugs, burned plugs, cracked plugs, wet plugs, any sign of electrical issues, etc. Clean the grounds on all of your coils. Clip and unclip the coil connectors a couple of times to refresh their contact surfaces. Check your battery voltage--low voltage is never a good thing. Start the car and check the charging voltage at idle. Same issue--low voltage is terrible for coils. Clean the engine ground strap and replace it if the braiding is corroded. Clean your battery ground strap, both ends. Clean the positive cable, both ends. Change your air filter if you have been neglecting it. Now you have: and engine that can breath, a known good voltage from the battery and alternator, and confidence in most of the electrical connections regarding the engine firing.

Then go to your fuel rail. Carefully unclip and reclip all fuel injector electrical connectors while inspecting for problems (any sign of fuel leakage). Run some injector cleaner in your tank to be sure you have clean injectors. Now you have some confidence your injectors are not contributing to the problem.

Clean your throttle body if you haven't done so in the last six months. Double check your air intake piping that it is firmly attached. Now you have: An engine that appears to be breathing correctly.

Then consider your fuel supply. The problem is happening at high RPMs just after accelerating. If you have not changed your fuel filter, they are due at 100,000 miles or so. (Aftermarket name brand is fine.) If you have not changed your fuel pump, keep in mind that you are experiencing the problem under load and the intermittent failure could be from a brief loss of fuel pressure that confuses the computer. Volvos chew through fuel pumps. My 2003 V70 is on its third pump at 112,000 miles.

 

I've read a lot about all these things the more I've researched so I'll be going through everything I can like you said. I've had the car for a couple months now after buying it from its original owner, they had tons of ser vice records but they have kind of neglected it towards the end. It's sitting with 180k on the odometer and a 3 year old battery. It's had some major work done recently as far as big ticket items but I'm not to sure on the pump. I'll be going through it all regardless today especially if the issue persist after the tune up. Thanks for the help.

 

Quick update, pulled plugs and coils. All five coils had cracks to some extent which was expected, however I did have oil pooling up top and it managed to seeped into the #2 spark plug tube. What gets me is that #4 was drenched with no signs of it coming from the top and #5 was worse. I know my pcv is likely clogged and will be replaced as well as an oil cap and the other four coils to accompany the one I already have and plugs. Now I can't help but think the cam cover seal may need to be replaced in order to replace the tube seals but is it worth it? Or should I replace the coils and plugs and my pcv system and hope it isn't as bad as before? I always do my own work but this job may be out of my reach unfortunately.

 

If you are having oil pool at the top of the cam where the coils are I would recommend to look at the oil vapor tube that attaches to the cam case (i.e. its the black tube that comes from the oil trap that snakes it's way through the intake manifold and into the top as it goes by oil cap on the left) once that tube is cracked it is a 6-7 hour job if you want to replace the oil trap and the lines that attach to it since it is located under the intake manifold.