bronchole
Driveway flexing!
- Joined
- May 13, 2009
- Messages
- 721
- Reaction score
- 51
- City, State
- Los Angeles, CA
- Year, Model & Trim Level
- 1997 Monsterneer
- Callsign
- KI6MCO
First off, I know that P0308 is a “misfire detected on number 8 cylinder”.
My rig:
1997 Mercury Mountaineer 5.0 AWD with the EGR port on top of the passenger side exhaust manifold/header
A couple months ago I did a bunch of stuff to run my Mountaineer thru smog:
Before preparing for the smog I was having a misfire/rough running issue that I primarily attributed to the spark plug wires being fried. They defiantly were fried from the exhaust gasses hitting the wire and baking it until it was brittle and falling apart. After I replaced the wires it seemed to be running much more smoothly. After 4 trips to the smog shop (1. replace the cold air intake, 2. Replace the oxygen sensor, 3. Replace the EGR upstream/downstream sensor, 4. Pass!) I finally got it thru smog and it was running better than it has in a long time. That was the most involved smog I have ever had to have done.
A few weeks ago I took it on a 2000+ mile road trip towing my 4500 pound trailer to Utah. About 250 miles in to the trip it started occasionally running rough and spitting out a P0308 code. Eventually it would stop running rough and I would clear the code. A few hundred miles later it would do the same thing.
Coincidentally at about 300 miles I had to replace the A/C blower motor relay. It had a meltdown that stopped the blower motor from working. Luckily it is a standard type relay.
When I got back from the trip I tried replacing the coil packs but that didn’t make a difference.
I am going to try swapping spark plug wires (if the #7 wire is long enough to reach) to see if it’s a spark plug wire issue. I’ll probably pull/replace the #8 spark plug also since it is pretty new.
The next area I am going to look at is the injectors. I ran several cans of fuel injector cleaner thru the system during the trip to see if that would clear up the issue. I didn’t really see any change. Still running the injector cleaner though, just in case.
What is the best methods for troubleshooting the injectors? I’m going to try to just unplug #8 and see what kind of difference that makes. I seem to remember there is some sort of on-board testing that an OBD2 reader can trigger for the computer to figure out if the injector is working correctly. Does that sound familiar? Hopefully I can find my Bluetooth OBD2 reader, its been a while since I have seen it.
Thanks for any help/suggestions.
Dan
My rig:
1997 Mercury Mountaineer 5.0 AWD with the EGR port on top of the passenger side exhaust manifold/header
A couple months ago I did a bunch of stuff to run my Mountaineer thru smog:
- Replace hoses that run from the EGR tube to the upstream/downstream sensor.
- Replace the upstream/downstream sensor.
- New spark plug wires.
- Sealed up various exhaust leaks including replacing the passenger side Torque Monster header that had cracked in a few places.
- Changed spark plugs.
- Replaced the MAC cold air intake with a stock air intake.
- Replace both upstream oxygen sensors.
Before preparing for the smog I was having a misfire/rough running issue that I primarily attributed to the spark plug wires being fried. They defiantly were fried from the exhaust gasses hitting the wire and baking it until it was brittle and falling apart. After I replaced the wires it seemed to be running much more smoothly. After 4 trips to the smog shop (1. replace the cold air intake, 2. Replace the oxygen sensor, 3. Replace the EGR upstream/downstream sensor, 4. Pass!) I finally got it thru smog and it was running better than it has in a long time. That was the most involved smog I have ever had to have done.
A few weeks ago I took it on a 2000+ mile road trip towing my 4500 pound trailer to Utah. About 250 miles in to the trip it started occasionally running rough and spitting out a P0308 code. Eventually it would stop running rough and I would clear the code. A few hundred miles later it would do the same thing.
Coincidentally at about 300 miles I had to replace the A/C blower motor relay. It had a meltdown that stopped the blower motor from working. Luckily it is a standard type relay.
When I got back from the trip I tried replacing the coil packs but that didn’t make a difference.
I am going to try swapping spark plug wires (if the #7 wire is long enough to reach) to see if it’s a spark plug wire issue. I’ll probably pull/replace the #8 spark plug also since it is pretty new.
The next area I am going to look at is the injectors. I ran several cans of fuel injector cleaner thru the system during the trip to see if that would clear up the issue. I didn’t really see any change. Still running the injector cleaner though, just in case.
What is the best methods for troubleshooting the injectors? I’m going to try to just unplug #8 and see what kind of difference that makes. I seem to remember there is some sort of on-board testing that an OBD2 reader can trigger for the computer to figure out if the injector is working correctly. Does that sound familiar? Hopefully I can find my Bluetooth OBD2 reader, its been a while since I have seen it.
Thanks for any help/suggestions.
Dan
