MY04 with a little more than 150k miles on it started getting misfires in 1 & 4, then random. Read the misfire thread in here which goes through the several possible causes. Spark plugs were replaced 10k miles ago for general maintenance & car ran fine. Once the misfire happened, I replaced all coil packs but it continued. The car would run fine after a cold start, only if I drove her to the gym & back & the car sat for an hour or so, once started it would have a rough idle(car shaking), would go away after a bit but normally within 10 or so minutes that's when the misfire code would appear. Replaced the injectors & after that the car would bog heavily in every gear, but after driving it a bit, the bog only happens in 3rd gear. When revs are up the car seems normal. It has thrown a code which I haven't been able to read yet, I assume misfire or possibly lean code. I have a fuel filter ready to be installed, but with everything else I wonder if that will fix it. I'm having the original injectors repaired & tested if this doesn't fix the issue. I should note I did the MAP sensor 'whack'. Other things I wonder about is TPS? or the car needing a valve adjustment?

Any help would be greatly appreciated. The car is a rebuilt title that I bought 11 years ago & has been great to me, but at this point it's not worth any costly repair, so I'm checking off the cheaper things.

Update: Installed new injectors & fuel filter. Did valve adjustment(surprisingly they weren't too far from spec). Now the issue is not misfire rather extreme bog in all grears yet car drives normal once rpms are about 5k or so. Car feels like it could stall out starting in first from dead stop. My next thought is FPR & then TPS.

Update(problem fixed): Took old injectors used to flush them with choke cleaner, reinstalled, bog is gone, car runs fine. No check engine.

 

When was the last time the valves were checked and adjusted? I would have checked that after replacing spark plugs. Are you still getting the exact same codes from before replacing any parts?

 

Valve adjustment would be good to try. Free to try if you can do it yourself.

i didn't have any driveability problems, but on cold starts my car would develop misfire on all cylinders CEL and it only went away after i did a valve adjustment. Your problem seems worse, but a valve adjustment may be something easy for you to try next.

I can't tell if you are still having misfires on only 1 and 4 or if it's always the random code at this point, but if it's ever just 1, 2 or 3 cylinders like that, you can move around coils, injectors and spark plugs to see if the misfire moves too. That can help track down faulty components, if any. Likewise, if you're experiencing misfires at idle, you can disconnect coils/injectors to see if it changes the engine behavior or not.

 

Unfortunately, they were never adjusted. I do have the tools to do so & do need to replace my valve cover gasket. So could two kill birds with one stone so to speak. Should I do the fuel filter or based on your experience, these symptoms are that of valves needing adjustment?

What tools do you need to turn the engine to top dead center? I just want to make sure I have the right socket.

 

I've seen some videos on how to do the valve adjustment & have the feeler gauges along with the tool to adjust the valve screw. How much does this cost to have a shop do it? Should I still do the fuel filter considering it has never been done? & what is priority?

I've moved around plugs & coil packs thinking the same thing you were but it didn't change & then it started reading random misfire.

 

If you have tools for adjustment diy it,or at least check them..

 

Yeah I'm just going to pull the valve cover check them, adjust if need be, & then replace my valve cover gasket. So at least it won't be a waste of time if valves are good.

Assuming issue persists(or the valves are within spec), I will do fuel filter. Assuming that is not the issue could it be the fuel pump itself or possible TPS?

 

would check fpr b4^^

 

Check your spark plug seals too. I had a misfire in cylinder #4, was going to swap spark plugs but didn't even got to the spark plugs. I found a bit of oil on my ignition coil in cylinder #4. Further inspection found oil on the cylinder #2 coil as well. I'm at 138k miles. So I just replaced everything:

https://www.s2ki.com/forums/introduc.../#post24581118

 

Maybe my mind isn't working since it's 5am but what is fpr? How do you check it?