Hey all,
This morning while driving home from work, my engine began to miss slightly at low-RPM with moderate throttle input. It rapidly became worse to the point where one cylinder was missing every five to ten rotations of the engine at both idle and running speed, though less so at RPMs above 3,000.
Fortunately I had my Snap-On scan tool in the car and was able to take a look at things before I got on the Mass 'Pike and committed to the rest of the drive home. There were no active or pending trouble codes, and all of the realtime data this scan tool can read looked normal. During the drive home, the misfire was most apparent during part-throttle acceleration and while ascending the small rollings hills on the highway. It was also very apparent when starting from a stop light after I got off the highway, and while the engine was hot it would miss at idle while in gear.
I drove home and once parked in my driveway, scanned the computer again for pending codes. This time it read P0320 - Continuous Memory Diagnostic Trouble Code (DTC) P0320 indicates two successive erratic Profile Ignition Pickup (PIP) pulses occurred resulting in a possible engine miss or stall.
I got on the phone with a friend (who happens to also be a member here) and had him look up possible causes of the code. Many internet search results pointed to the crank sensor, while others said to check the secondary ignition components. He found a great document that has a crank sensor "pinpoint" test which allows you to determine the exact nature of the fault:
http://home.comcast.net/~thefordmaniac/03CKPtest.doc
After I woke up from a few hours rest, I got back to troubleshooting the problem. I performed the first test outlined in the above guide and saw that there was indeed a signal being sent from the crank sensor to the PCM when cranking - this ruled out the crank sensor as the cause of the issue. I then moved on to check the camshaft position sensor, which is known to be a fairly common failure part. I pulled the connector for this sensor while the engine was running and detected no change at all in the way the engine ran; the misfire remained but did not get any worse. I replaced the camshaft position sensor with a new part from the local auto parts store...the price was just under $15 so I figured I might as well give it a shot. Well, fortunately this is a fairly inexpensive part as replacing it also made no difference.
At this point I decided to pull every single coil and plug to get an idea of what was going on in each cylinder. Some of the coil boots had a bit of oil on them, though none were submerged. All of the plugs looked great...the insulators were mostly still white and the electrodes were just slightly graying. None of the plugs were wet or fouled-looking, which was relieving and corresponded with the fact that this was an intermittent misfire.
In looking through all of the monitoring parameters on the scan tool, I noticed many of them were disabled...including the misfire detection parameter. With the fact that Lonnie's tune shut off a good bit of my PCM (EGR, rear 02's) in mind, I decided to reflash the PCM back to stock. Sure enough, when I started the car again with the factory program, the misfire detection parameter was now enabled. After about ten minutes of ilding and the occasional engine rev, the PCM threw another P0320 in the pending codes list but this time specified a misfire in cylinder #2. This was great news, because it narrowed the issue down to a few specific potential part failures (bad plug, bad coil/coil boot) rather than some unknown electrical gremlin.
Both I and the friend I spoke of above felt as though the issue was characteristic of a bad coil, since the misfire became especially apparent during low-RPM, moderate-to-high load conditions. I switched the coils on the #1 and #2 cylinders and restarted the car in an attempt to validate a bad coil. I allowed the car to run for another ten to fifteen minutes and checked the pending codes occasionally throughout this time. I was happy to see that the PCM now detected a misfire in cylinder #1, meaning that the misfire had followed the coil from cylinder #2.
One new coil and $46.00 later, the engine is running great with no signs of misfiring. I reset the PCM and reloaded the performance tune after a short test drive - no more issues.
This was great news, because now I won't have to delay installing 3.73's with a Trak-Lok tomorrow afternoon
Hope this helps someone,
-Dom
This morning while driving home from work, my engine began to miss slightly at low-RPM with moderate throttle input. It rapidly became worse to the point where one cylinder was missing every five to ten rotations of the engine at both idle and running speed, though less so at RPMs above 3,000.
Fortunately I had my Snap-On scan tool in the car and was able to take a look at things before I got on the Mass 'Pike and committed to the rest of the drive home. There were no active or pending trouble codes, and all of the realtime data this scan tool can read looked normal. During the drive home, the misfire was most apparent during part-throttle acceleration and while ascending the small rollings hills on the highway. It was also very apparent when starting from a stop light after I got off the highway, and while the engine was hot it would miss at idle while in gear.
I drove home and once parked in my driveway, scanned the computer again for pending codes. This time it read P0320 - Continuous Memory Diagnostic Trouble Code (DTC) P0320 indicates two successive erratic Profile Ignition Pickup (PIP) pulses occurred resulting in a possible engine miss or stall.
I got on the phone with a friend (who happens to also be a member here) and had him look up possible causes of the code. Many internet search results pointed to the crank sensor, while others said to check the secondary ignition components. He found a great document that has a crank sensor "pinpoint" test which allows you to determine the exact nature of the fault:
http://home.comcast.net/~thefordmaniac/03CKPtest.doc
After I woke up from a few hours rest, I got back to troubleshooting the problem. I performed the first test outlined in the above guide and saw that there was indeed a signal being sent from the crank sensor to the PCM when cranking - this ruled out the crank sensor as the cause of the issue. I then moved on to check the camshaft position sensor, which is known to be a fairly common failure part. I pulled the connector for this sensor while the engine was running and detected no change at all in the way the engine ran; the misfire remained but did not get any worse. I replaced the camshaft position sensor with a new part from the local auto parts store...the price was just under $15 so I figured I might as well give it a shot. Well, fortunately this is a fairly inexpensive part as replacing it also made no difference.
At this point I decided to pull every single coil and plug to get an idea of what was going on in each cylinder. Some of the coil boots had a bit of oil on them, though none were submerged. All of the plugs looked great...the insulators were mostly still white and the electrodes were just slightly graying. None of the plugs were wet or fouled-looking, which was relieving and corresponded with the fact that this was an intermittent misfire.
In looking through all of the monitoring parameters on the scan tool, I noticed many of them were disabled...including the misfire detection parameter. With the fact that Lonnie's tune shut off a good bit of my PCM (EGR, rear 02's) in mind, I decided to reflash the PCM back to stock. Sure enough, when I started the car again with the factory program, the misfire detection parameter was now enabled. After about ten minutes of ilding and the occasional engine rev, the PCM threw another P0320 in the pending codes list but this time specified a misfire in cylinder #2. This was great news, because it narrowed the issue down to a few specific potential part failures (bad plug, bad coil/coil boot) rather than some unknown electrical gremlin.
Both I and the friend I spoke of above felt as though the issue was characteristic of a bad coil, since the misfire became especially apparent during low-RPM, moderate-to-high load conditions. I switched the coils on the #1 and #2 cylinders and restarted the car in an attempt to validate a bad coil. I allowed the car to run for another ten to fifteen minutes and checked the pending codes occasionally throughout this time. I was happy to see that the PCM now detected a misfire in cylinder #1, meaning that the misfire had followed the coil from cylinder #2.
One new coil and $46.00 later, the engine is running great with no signs of misfiring. I reset the PCM and reloaded the performance tune after a short test drive - no more issues.
This was great news, because now I won't have to delay installing 3.73's with a Trak-Lok tomorrow afternoon
Hope this helps someone,
-Dom
