Have run out of ideas, and turning to the forum for help. Here're the particulars:
-`99 Grand Cherokee Limited, 4.7 V8, 160K miles, all stock
- vehicle starts fine, voltmeter shows 14+ volts at idle
- drive down the road five miles or so, and voltmeter starts to drop
- drive far enough, and warning chime announces "Check Gauges"; voltmeter shows below battery voltage; shut the engine off, and it won't restart - battery flat. The three times that's happened, if jump-started, it starts right up and shows 14+ volts again.
- at times, when slowing to a near-stop, the voltage will come back up to 14V and remain there
- at times, during or after the "event", transmission seems to attempt to downshift, then upshift; what's felt is a driveline shock like a "kick in the rear"
- have experienced only one DTC - P0108 - MAP sensor; sensor tested okay at 4~5V from outside wires to ground (plug disconnected, key on); voltage from center wire to ground fluctuates with TPS movement
- at times, when the engine is below operating temperature, when coming to a full stop in gear, idle speed will drop low enough for the engine to stall. Starts right back up. Idle speed seems to stabilize at 650 after a brief higher level.
I can't say for certain how much of what I've described is connected to one another, I'm just throwing everything out there in hopes someone can make sense of it all.
There are no other problems I've observed. Temperature controls, heated seats, lights, windows all seem to work fine.
What I've done so far:
- replaced battery & clamps
- confirmed ground cables connected and active at cylinder heads, right front fender at power distribution box; engine to body, exhaust to body
- tested MAP sensor as noted above
- tested alternator both with Auto Meter hand-held and off-car: passed all checks.
- looked at the wiring going into the driver's door; there appears to have been a previous repair in there, but it's too cold to work on it right now.
At present, this vehicle is not reliable to drive, so I'm writing this with fingers crossed, hoping someone else has been down this road to a fix. Any help will be appreciated.
99% sure the alternator is toast. It checked out ok because it is an intermittent failure. Stalling, DTC for MAP, etc are all flukes related to low voltage; ignore. The new battery's life won't last very long without a fully operational charging system, you might need to replace as well once you replace the alternator (unless it is a dry cell battery).
Thanks for the suggestions - all help is appreciated!
Update: no-charge situation is now constant. Only thing new so far is that I found the ground strap from the body to the transmission frayed to the degree that only a few strands were holding it together (it lies on top of the exhaust pipe on its way to the trans, and I guess the years of vibration wore it through). I missed that before. Will get a new one this week.
Suggestion about the alternator seems a good one. It's been tested four times so far, both on-car and off, but now that the no-charge is constant, maybe the problem will show up on the fifth test?
That ground strap is nothing more than an improvement to the AM radio reception. Doesn't hurt to fix though.
The alternator is certainly the issue. I was able to squeeze a few more miles from it by smacking the housing with a hammer. It was done though. Same symptoms as you.
You'll do a little better with a replacement by getting the Durango replacement alternator. It costs less too. Direct fit and puts out 160 amp as opposed to about 128 from the Jeep unit. The only small modification is the diameter of the copper ring connector to the alternator....it needs to be opened up slightly to fit.
2000 Laredo 4.7L Selec-Trac. 177K miles, Leather, 245 tires, tow package, crappy CD changer, full size spare, roof cross-rails & sunroof. Changes & fixes: Rear Addco sway bar & greasble bushings, upgraded headlights, upgraded tail lights, new hood struts (replaced 2X), new rear hatchglass struts, new radiator (replaced 3X), new oil pressure sending unit (replaced 4X), 2 new speed sensors, 2 new door lock actuators, new ignition key cylinder, chrome front tow hooks, Mobil 1 Synthetic 5/30, Purolator Pure One oil filter, EBC slotted & dimpled rotors, EBC Greenstuff pads, new front shocks (replaced 3X), new rear shocks (replaced 2X), new IRO steering stabilizer, new timing chain cover, new water pump, thermostat, new thermostat housing, new high pressure power steering hose, Michelin-X radials, new sunroof assembly, new single-piece lug nuts, new exhaust manifold studs & gasket on driver's side, new Durango alternator. Jeepforum.com sticker, Visit cobaltboatsforum.com when you can!