Originally had two misfiring cylinders (no 2 and no 7). Swapped out all coil packs and car ran fantastic for 3-4 days with no codes thrown.
P0302 came back even worse than before with hard misfire (blinking check engine). Have since:
1- Swapped spark plug and code remains in cylinder 2.
2- Swapped injectors and code remains in cylinder 2.
3- Swapped new coil packs just to be sure. 4- Changed the fuel filter as it was due.
Anyone have any ideas? I’m stumped at this point. Maybe the cats or a camshaft position sensor?
It runs great for the first 30 seconds then I start getting blinking check engine light. Power is still there but I hear the occasional pop out of the exhaust and it runs slightly rough.
With a “stubborn” P0302 you can forget cats and cam or crank position sensors for a while.
I don’t know how difficult it is to check the compression on this engine configuration, but it would be a best first step.
I also don’t know easy it is on this configuration to get to the fuel injectors, but step #2 would be to swap the #2 fuel injector with another to see if the misfire follows the injector.
Mis-“fire” is a bit of a misnomer. It should be called “mis-combustion” - as in the air/fuel mixture didn’t explode. That can be from lack of spark (the “fire”), or fuel (injector problem), or air (unlikely if confined to one cylinder), or compression.
OK, you have a 2006, that 7 years ago in 2017 you had clutch issues, that is normally a high mileage issue, but I have yet to see how many miles are on this thing…
How many miles are on the engine/vehicle???
Clearly the engine has an internal mechanical problem that no amount of parts swapping will fix. The OP has done this and proved it is not an ignition or injector problem.
A compression test isn’t hard to do on these engines. Pull the fuel pump relay and you can crank the engine from the starter relay by jumping across the terminals… both are in the underhood fuse box.
If cylinder #2 reads low, and I’m sure it will, pull the valve cover over #2. Look for broken rocker arms, broken valve springs or if one of the 3 valves is stuck open. Hopefully it is a broken spring or rocker and that the rocker hasn’t torn up the cam.
If you can’t find a reason that cylinder is dead, time either dig deeper into the engine, or search for a used replacement.
A 260hp 4.6 ohc is different than a pushrod 302 for head replacement. A bare head does not include cams and you have to work on timing chain as well. Is what it is. I guess you can’t fight progress.
I kinda thought that was where this was all headed but needed to hear it from someone else, I think.
I’m probably just going to trade it in and get another car instead of futzing around with it. Only reason I haven’t is because I have a less than five mile commute to work. Seemed like a waste as long as this one worked reliably.
It seems like you’ve done all the simple tests for the problem, so I expect the folks above are right, there’s an internal engine problem. An engine compression test definitely makes sense at this point. There’s one puzzle remaining though, why did the symptoms get remarkably better for 3-4 days, then got worse again? If the compression test shows a problem, it’s possibly a simple problem, like a valve is sticking. If it shows there’s not a compression problem, make sure the battery and alternator are working to spec, and that the engine compartment ground connections are in good shape, especially for the cylinder head and battery. The electrical path between the pcm and the coils and injectors for that cylinder should be checked with an ohm meter, line by line, for broken or “iffy” connections too. If you have access to a lab o’scope, comparing the ignition and injector waveforms between the faulty cylinder and one that seems to be working might provide an important clue. That’s probably where I’d start were I diy’ering the job. .
If you feel lucky you could just try the common methods to unstick a stuck valve, chemical treatments, etc.