Hello all,
We really need some help. My son has a 04 Rubi 4.0L 5-speed with about 142K on it. We've owned it since new. He suddenly started getting a misfire on cylinder 1. It initially threw the P0301 code. 95% of the time, it runs fine when it's cold, then starts to misfire when it's about half warmed up. Because it happens warmed up, I thought it was a bad sensor but so far no luck. Sometimes it's consistent, sometimes it's not. When I say not consistent, I mean sometimes it sounds like there's a couple misfires from different cylinders but no code to verify that. We've replaced almost every sensor with factory (or forum recommended) ones. We've tried 2 different brand plugs (also recommended here/APP985). Right now, it's a consistent miss on 1. I'm 99% sure it's cylinder 1 because we've pulled the fuel injector connector while it's missing and it made no change while pulling the others have caused a change in idle. Below is the list of what we've done. ANY ideas on where to go with this next? We did take it to a mechanic with no luck (what he did is listed below also). Thank anyone in advance for ANY suggestions. It's driving me nuts.
The ONE thing we've done that seems to give us a hint is that we pulled the coil rail, and grounded all the plugs directly to the battery and cranked the engine. The spark was yellow/weak and inconsistent. We've kept a battery charger hooked up to the battery to make sure it has plenty of power. We also tried jumping another battery to it.
1. Changed the 2 upstream O2 sensors
2. New Cam sensor
3. new crank sensor
4. tested injectors, #1 was reading low so it was replaced.
5. new coil rail
6. New MAP sensor
7. new coolant temp sensor
8. checked compression - was OK.
9. Ran a can of seafoam through
10. New plugs (2 different kinds, also tried adjusting the gap)
11. Getting full power (12+V) at the injector (checked #1)
12. looked for vacuum leaks and haven't found any
13. We recently had the valve cover off and the oil pan off - engine internals looked impeccable.
Mechanic:
1. Checked compression
2. scoped engine
3. checked fuel system
We really need some help. My son has a 04 Rubi 4.0L 5-speed with about 142K on it. We've owned it since new. He suddenly started getting a misfire on cylinder 1. It initially threw the P0301 code. 95% of the time, it runs fine when it's cold, then starts to misfire when it's about half warmed up. Because it happens warmed up, I thought it was a bad sensor but so far no luck. Sometimes it's consistent, sometimes it's not. When I say not consistent, I mean sometimes it sounds like there's a couple misfires from different cylinders but no code to verify that. We've replaced almost every sensor with factory (or forum recommended) ones. We've tried 2 different brand plugs (also recommended here/APP985). Right now, it's a consistent miss on 1. I'm 99% sure it's cylinder 1 because we've pulled the fuel injector connector while it's missing and it made no change while pulling the others have caused a change in idle. Below is the list of what we've done. ANY ideas on where to go with this next? We did take it to a mechanic with no luck (what he did is listed below also). Thank anyone in advance for ANY suggestions. It's driving me nuts.
The ONE thing we've done that seems to give us a hint is that we pulled the coil rail, and grounded all the plugs directly to the battery and cranked the engine. The spark was yellow/weak and inconsistent. We've kept a battery charger hooked up to the battery to make sure it has plenty of power. We also tried jumping another battery to it.
1. Changed the 2 upstream O2 sensors
2. New Cam sensor
3. new crank sensor
4. tested injectors, #1 was reading low so it was replaced.
5. new coil rail
6. New MAP sensor
7. new coolant temp sensor
8. checked compression - was OK.
9. Ran a can of seafoam through
10. New plugs (2 different kinds, also tried adjusting the gap)
11. Getting full power (12+V) at the injector (checked #1)
12. looked for vacuum leaks and haven't found any
13. We recently had the valve cover off and the oil pan off - engine internals looked impeccable.
Mechanic:
1. Checked compression
2. scoped engine
3. checked fuel system