2003 6.8L Excursion mystery problem
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2003 6.8L Excursion mystery problem
My 2003 6.8L Excursion has an issue several mechanics can't figure out. They just keep throwing parts in on my wallet. A few thousand miles ago it would once in a blue moon stall when put in reverse. That became more frequent as time has gone...now virtually every time. In addition, it has started doing it in drive as well, sometimes. Scoop: Brand new battery, TPS, IAC and tranny fluid. Also throttle body scrub. It doesn't quite die now, but idles at 400-500rpm. Can be in drive at stop, shift to 2nd or 1st and, low idle. Back to drive, same. Reverse same. Back to D, often good idle again. Been stopped with fine idle only to have it suddenly go low by itself. Have experienced numerous times, turning on or off AC can also cause, or rectify, idle. If at low idle, allowing the wheels to roll with no accelerator can bring rpms to normal as well. Runs perfectly when cold, no issues whatsoever. Tranny has never had any hiccups shifting or performing at all. Vehicle has 185k, 50k of which I have put on it.
Has anybody ever heard of this type of issue?
Has anybody ever heard of this type of issue?
Logistics Pro
Joined: Nov 2004
Posts: 4,795
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Some similar threads with ideas
https://www.ford-trucks.com/forums/9...n-reverse.html
https://www.ford-trucks.com/forums/1...n-reverse.html
https://www.ford-trucks.com/forums/9...n-reverse.html
https://www.ford-trucks.com/forums/1...n-reverse.html
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,725
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From: SE Florida
Put 0-350 psi pressure gauge in the transmission test port. The port is on the driver's side of the trans, towards the front of the trans, just above the pan. It has a black hex head plug in it from the factory. The thread is 1/8" NPT.
Check pressures at idle in every position (PRND21) and at stall in RD21. Stall is when you have your left foot as hard on the brake pedal as you can push it and then press the accelerator pedal to the floor with your right foot.
CAUTION - DO NOT HOLD STALL FOR MORE THAN 5 (FIVE) SECONDS AT A TIME!! IDLE OR FAST IDLE IN PARK OR NEUTRAL FOR AT LEAST 30 SECONDS AFTER EACH STALL TEST.
Check pressures at idle in every position (PRND21) and at stall in RD21. Stall is when you have your left foot as hard on the brake pedal as you can push it and then press the accelerator pedal to the floor with your right foot.
CAUTION - DO NOT HOLD STALL FOR MORE THAN 5 (FIVE) SECONDS AT A TIME!! IDLE OR FAST IDLE IN PARK OR NEUTRAL FOR AT LEAST 30 SECONDS AFTER EACH STALL TEST.
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