||11-07-2013 08:24 PM
4.7 dying without warning
I've read some similar issues, but I have enough unique details that I figured it warranted a new thread, so here goes. This will be a long post since I'm trying to include all the details I can remember.
At idle, sitting at a light, in the driveway, carwash, or wherever, my engine will just die. It doesn't sputter or idle rough or anything beforehand, it just very quietly dies. Sometimes I don't even notice when it dies until I try to move. It always fires right back up, usually with no sputtering or anything, but occasionally it will idle rough for a second immediately after restarting. I have no engine codes, pending or otherwise, to indicate what the problem is and I haven't noticed a change in power, mileage, shifting, or anything else.
It also happened twice while driving a few weeks ago. I was pulling a small utility trailer (about 400#) with a new HP44 on it, so about 800-900# total on the highway in OD and the Jeep jerked violently and I could feel/hear the driveline go from driving to coasting and immediately back to driving. At first I was afraid it was a transmission issue when this happened while driving, but after further thought and analyzing shifts and what happened immediately afterwards, it seems more like the engine died for about 1/2 second and then fired right back up. Immediately after the jerk, I looked at my gauges and my speedometer was swinging from 0 back up to 60mph like the gauges had been briefly without power/signal. After the second jerk (about 30 seconds after the first), I pulled over and crawled under the Jeep looking for any kind of leaks, driveline slack, etc, but did not see or smell anything out of the ordinary. I drove the rest of the way home (another 2 hours) with OD turned off. It did not happen again while driving, but while waiting at a light about 30 minutes later, the engine died again. Popped it into N and it started right back up and ran great the rest of the way home.
To me, this seems like a sensor issue. Maybe a crankshaft or cam position sensor going bad. I don't think it is a wiring harness shorting/grounding issue since it always fires right back up and rough roads or vibration doesn't seem to have an effect on the problem. Does anyone have any insight on what could be causing this problem? It's very annoying, but so far hasn't left me stranded anywhere since it does always start right back up.
Any help would be greatly appreciated.
On a possibly related note, I just put an Ultra Gauge in the Jeep about 3 weeks ago so I could monitor temperatures, mileage, etc and it will randomly blank out for a second like it's not receiving any signals from the OBDII port and then return to normal. I have alarms set for engine load, intake air temp, coolant temp, etc, and these alarms will randomly go off when no abnormal conditions exist. For example, while cruising along at about 1700rpm, the alarm will go off saying my engine RPM is 4500 or so.
Sorry for the long post, and thanks in advance for any help. If you need more details or have specific questions, please ask and I will answer as best I can.