ym42

Ok, here is a small update - the car is running even worse when cold. It has multiple misfire codes: random misfire, misfire cyl 6, cyl 2. When I just start it, or when it's warmed up for a while it's smooth and gets a great gas mileage. What can be wrong? I have a feeling it's some kind of temp/air sensor. When I start car runs ok, then starts misfiring horribly, running rough, and after about 2 minutes of driving it's all ok again. It kind sounds like my friends Beamer with a faulty MAP sensor... And it's usually when I press gas pedal more that the misfires develop... I changed the oxygen sensors recently but can they even have anything to do with it?

BigDinTexas

Have you tried to replace the plugs on 6 and 2 with new ones? I know you said you moved them around, and the misfire followed the plugs, right?

Since the problem followed the plug, it would seem we can eliminate fuel injectors and the COPs... Try the cheapo Motorcraft plugs since they are inexpensive and might correct the issue immediately.

Doubtful it is an O2 sensor since cylinders 6 & 2 fire into different exhaust manifolds and thus are read by separate O2 sensors.

Also, from my purely non-technically proficient brain, your mention of the problem being at cylinders 6 & 2 is somewhat making me think... When I look at this image of the cylinders, and seeing that 6&2 are adjacent to each other on the crank shaft, I wonder if there is an oiling problem with your journals? This is waaaaaaaay out of the realm of possibility and would likely be experiencing other problems noises, and I am purely pulling this out of my rear, but it could be something to consider since they are across from each other, atleast to start looking at a different possible cause.


Don

ym42

Cool. Thanks. I think I will try the Motorcraft plugs... I'm not confident in the earlier diagnosis, because even though I did replace the plug things did not get better, and the misfires only got worse and on multiple cylinders. It feels like something is clearly deteriorating... But otherwise the car runs fine...

Stoenr

swap coils around?

ym42

Stoenr - I would if it was just one cylinder, but I get the random misfires code among others and it has been getting worse... Only happens about a minute after starting the engine and for a couple of minutes until the temp needle gets to the first position on the left. Then running smooth. I mean the car does not start with misfires, they appear after about a minute of running, especially under partial load on lower RPM.

hammeron

I'm going with vacuum leak or cat(s) going bad, as my top two guesses.

Hope you get it sorted out soon, if it's not already.

ym42

I think cats should not affect ignition systems...

MADSCOTSMAN

Might seem silly, but this sounds unusually similar to the way my car was acting when my alternator was going bad. I only had what felt like surged when the night before was either cold or wet. This was before getitng the p0340 codes 4-5 months later.

ym42

Did you have any misfires? Yes, it's getting worse but at first cold and wet night were the triggers... But the voltage is good and the battery cranks well...

MADSCOTSMAN

Not sure what a misfire would sound or feel like (like a backfire under the hood?!?). I didn't have any sounds, just could feel the car wasn't right via the gas pedal and watching the tach. Basically my symptoms were after a colder or wet night, I would drive to work the next morning and when I got on the highway up to about 55 and hold the throttle so the car would remain at that speed, the car would feel like it does if you were to keep pushing down the accelerator and letting up (like a jerking or "missing-studdering"). I went a s far as to set the cruise control and let my foot off the pedal to see if it still occured and it did. It did not happen above or below 55, only right at 55. The dealership threw their arms up since there were no codes and they could not reproduce it (Assuming I was crazy probably). I drove with it like this for almost a year with it occuring randomly until the "wrench" light came on one day and Autozone found the p0340 codes which I think was the left cam position sensor or something like that. I had them clear the codes and then had to clear them again a few times myself with my tuner and started researching the codes to see if I could replace the sensor myself (was beyond warranty at this point). As luck would have it, another day I went out and my car would not start, so I jumped it with my wifes car and went to Advanced Auto Parts to look at getting a new battery. They tested my battery and alternator and both were "bad". After replacing the alternator and battery myself, the issue resolved itself. Never made that connection between the alternator-battery-sensor-code until reading some of the posts on here as to how others had replaced the sensor just to have to turn around and replace the alternator as well. I just planned to have to still change the sensor after the alternator/battery fiasco, but have not had the symptoms or the code again, since replacing the battery and alternator.