2000 Lincoln LS dies when gas is pressed hard or hesitates very hard

JOSHUAFENDER755

MEMBER
2000 LINCOLN LS
3.9L
V8
2WD
AUTOMATIC
150,000 MILES

I have a 2000 lincoln ls that I just bought a month ago, I am not very aware of how it was maintained but seems to be in great condition. I noticed a problem that confuses me, The check charging system light comes on after the vehicle warms up then goes out and comes back on when driving the entire time the vehicle is in motion. When the vehicle is turned off and restarted the vehicle shows no errors in the charging system for a few minutes and then it resumes its issues. I replaced the battery and cleaned the terminals with no effect. The alternator was checked by the auto parts store and they told me the charging system and battery were fine. The problem does not go away and continues everytime the vehicle is driven. The other day I was on the freeway and attempted to pass a slow moving vehicle by pressing hard on the gas to engage the passing gear, the vehicle responded poorly with hesitation and then with a burst of speed and then the vehicle died and the lights on the dash dimmed and returned. I dont know if this is a result of the alternator not supplying the vehicle with the power that it needed when the vehicle attempted to increase speed sharply or if there is another issue at hand. There are no DTC and never has been. Concerned that the issue will get worse and leave me stranded somewhere. Please advize me on the best course of action to take and what the possibilities are. This type of vehicle is completely ran by computer and very complicated so I dont know why I dont have any DTC's if the alternator is going out, just a check charging system message on the onboard display panel.

1 Reply

CARADIODOC

MECHANIC
33,916 POSTS

You're right to be concerned it's going to let you sit. The mistake that was made is the charging system is failing intermittently and that's when any testing has to be done. If it's tested while the problem isn't occurring, of course it's going to test okay.

The most common cause of intermittent operation of the generator on any brand of car is worn internal brushes. Those are real easy to replace on most Chrysler products, often without removing the alternator from the engine. Ford went to a similar, real nice design in the '90s, but by 2000 the engineers figured out it was too easy to diagnose and repair so they buried the voltage regulator and test points, and made servicing the unit very difficult. On the older ones there were two key test points right on the back. One was even labeled as such. Those made it real easy to determine if you needed a voltage regulator, brushes, or if it was more serious.

Output of the generator is not monitored by the Engine Computer, so it's not going to have a diagnostic fault code telling you what's wrong like they do on Chryslers. The only thing it could potentially set is a code related to low system voltage, but you already know that from the warning light and the "Volts" gauge on the dash. Low voltage adversely affects the many computers on the car making them do weird and intermittent things, so don't concern yourself yet with the engine running problem unless it continues after the generator is replaced. Worn brushes can continue to work on and off for weeks or months, but they will stop working for longer and longer periods of time as they continue to wear down and make intermittent contact. The car will be running on just the battery, and with the head lights and heater fan off, that won't last much over an hour before the engine stalls.