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I checked the resistance between the prongs: zero on the suspect coil, and zero on the other coil. I then tested the continuity of the green and red wires from the point of connection to the suspect coil to their connection on the firewall. Both checked good for continuity.
Not exactly sure on the technical aspect (my competence) of swapping the injector with another one...if I did that, I assume I would eventually get the same trouble code for the cylinder I swapped with (thus isolating that injector)?
I was able to verify that the #2 injector is working, but that is all.
I ran the engine briefly with the #2 injector disconnected from elec pwr. I verified voltage to the injector and injector continuity. The engine ran obviously more smoothly with power to the injector connected. I know that doesn't necessarily rule out a problem with the injector, but does rule out the #2 injector electrical circuit and functioning of the injector.
Based on some of the other possible causes you've mentioned, I'm wondering if any of those can be ruled out based on the fact that P0302 was the only malfunction code. There were no other codes or pending codes. In other words, since I had no code indicating a problem with the EGR can that be ruled out?
By the way, here's a little more info to go on: the fuel filter was changed with the timing belt at 105k (about 5k miles ago). The spark plugs have less than 20k miles on them. The #2 spark plug electrodes are whitish gray and dry.
Unfortunately, I may be nearing the end of what I have the competence and equipment to check (ie cylinder compression, fuel pressure). Other than changing the parts, can I check coil voltage or spark plug wire integrity? There is a small grayish white area on the wire, but as I previously mentioned, the #2 spark plug wire's resistance was the same as the other one.
Are injector cleaning products that are added to the gas a waste of money in your opinion? Might help? Can't hurt?
The wiring showing the grayish spot could indicate a possible opening. The test was good but that doesnt mean that wire could be experiencing problems. I would consider it a good idea to replace. The plug sounds to me like its firing well from the nice burning but wouldnt be a bad idea to throw some new ones in making sure to gap them correctly. The egr valve is a very hard thing to diagnose but even though there is not a code it could be sticking causing problems. I would first rule out the plug and wire by replacing them. I believe the injector cleaners do help and would suggest a bottle. A compression test is pretty easy to do you will just need a compression tester from your auto parts store. Same with the fuel pressure tester there is a port on the fuel rail where the injectors are you connect the tester to. These tests will verify there is not a fuel problem to the injectors and also that there is not any kind of mechanical issue with the engine. But I would first replace the plug and the wire atleast on that cylinder to ensure the plug wire is not loosing some signal. That is what I believe the problem is since these items are inexpensive I would start there then I would bring the car to autozone and have them clear the code see if this takes care of the issue. Thank You
I still have a problem. This is a summary of what I've done and where I'm at:
1. Started with OBD code P0302 (only code present) -- misfire in #2 cylinder.
2. Erased code. Swapped #1 and #2 plug wires. Code P0302 came back. Assumed problem was not the #2 plug wire.
3. Erased code. Swapped the #1 and #2 spark plugs. Code P0302 came back. Assumed problem was not the #2 spark plug.
4. Erased code. Swapped the #3 and #4 coils, expecting if the problem was in the #3 coil, I would now have a misfire in #1. I got good news / bad news: a new code: P0303 -- misfire in #3. Since the #4 coil (now in cyl #3) had not previously been linked in any way to the previous #2 misfire and the #3 coil (now in cyl #4) is not linked to the current code, I've made the following conclusions: I can eliminate the following possible causes: plugs, plug wires, coils, cylinder compression problem, fuel injector, fuel, fuel pressure, EGR valve.
It seems the only thing the two codes have ever shared in common is something in the wiring upstream of the connection to the #3 cylinder coil. What do you think about my logic and what would you suggest for further troubleshooting?