Ok so I'm at my wits end with this. I recently started getting rough idling after long drives and eventually the Jeep through a P0303 misfire. I initially thought it was a heat soak issue as I have had that problem before so I replaced all the injectors, and installed the DEI heat shield. No luck, and the problem has gotten worse. Before I'd have to drive for hours before it was an issue but now I start having misfires and rough idle after twenty minutes of driving.
So far, this is what I've done.
1. I already replaced the injectors, and checked the wiring by using a noid test light.
All injectors are getting power and seem to be pulsing normally. I cannot atleast see any damaged wiring.
2. I also tried replacing the coil rail with another one to see if it resolves the issue. I also pulled all the spark plugs and made sure they looked good and were gapped correctly. They were. I even swapped plugs with cylinder # 2 to see if the misfire follows and it did not.
3. I had a spare camshaft sensor on hand so I tried that too. No luck, same results.
4. I disconnected the O2 sensors as I heard this might cause misfires. No luck, still throwing the code.
5. I compression tested the engine at 160k miles and got perfect numbers. Granted I did not do a leakdown test, and now the Jeep has 188k miles.
The Jeep smells like gas and the misfire issue seems to get worse the longer you drive. Here is the weirdest part. Even though injector #3 is getting power, if I pull the plug off the injector there is no difference in idle. But I replaced the injectors? So I doubt that one is bad. What does this indicate? I know usually when you pull the plug and there is no difference in idle that means the injector is bad, but I've already replaced them?
So far, this is what I've done.
1. I already replaced the injectors, and checked the wiring by using a noid test light.
All injectors are getting power and seem to be pulsing normally. I cannot atleast see any damaged wiring.
2. I also tried replacing the coil rail with another one to see if it resolves the issue. I also pulled all the spark plugs and made sure they looked good and were gapped correctly. They were. I even swapped plugs with cylinder # 2 to see if the misfire follows and it did not.
3. I had a spare camshaft sensor on hand so I tried that too. No luck, same results.
4. I disconnected the O2 sensors as I heard this might cause misfires. No luck, still throwing the code.
5. I compression tested the engine at 160k miles and got perfect numbers. Granted I did not do a leakdown test, and now the Jeep has 188k miles.
The Jeep smells like gas and the misfire issue seems to get worse the longer you drive. Here is the weirdest part. Even though injector #3 is getting power, if I pull the plug off the injector there is no difference in idle. But I replaced the injectors? So I doubt that one is bad. What does this indicate? I know usually when you pull the plug and there is no difference in idle that means the injector is bad, but I've already replaced them?
