Patient is a 2005 Ford Taurus with the base engine (3.0L 12V Vulcan V6; NOT the 24V Duratec of the same displacement and cylinder count). It has right around 144,000 miles.
This morning, on startup, it idled at 1200 RPM, then 800, then 600, then chugged for a few seconds at 400 and then stalled.
On restart, I idled it at 2000 RPM by manually increasing throttle for about 20 seconds. After that I released the throttled, at which point the sequence from the above paragraph repeated itself.
The alternator is known to be on the way out.
Would the alternator do this?
Something else?
Different make & model, but my 1995 Nissan XE pickup went through similar issues a few years back. The culprit was the distributor cap, and replacing the cap alone (as opposed to cap + distributor) took care of the problem.
I do think, though, that the OP’s symptoms can have many causes.
How is the alternator known to be on the way out?
What you describe isn’t a normal symptom of a bad alternator, but I don’t think it’s impossible. It sounds more typical of a vacuum leak or an EGR problem. It sounds to me like the idle control valve itself is working, but there’s a few sensors that could be feeding the computer bad data that could also cause it. Odd voltages coming out of the alternator might cause or exacerbate a sensor problem. A mechanic with a scan tool should be able figure it out pretty quickly. If you’re DIY-ing it, it could be worth getting the alternator fixed before throwing any more time and parts at it.
I’m fairly certain this car uses distributorless ignition.
A bad alternator, water pump, AC compressor, etc CAN but immense load on an engine as it is taking way more force to turn them with bearings that have ground themselves into scrap. In my case they also made a bunch of noise and vibration.
The father of the vehicle’s owner, who is several counties away, told the owner that the alternator is on the way out.
Okay.
Code is P1633.
While I had it running, I forced it to maintain 2000 RPM.
This required a fuel burn rate of 1.6 gallons per hour.
Just got a new tidbit of data:
The AC compressor clutch apparently sticks sometimes on this thing.
Amazing how people volunteer new information to you when you ask…
Everybody else is guessing so why not me too?
The throttle position sensor is a common cause of this problem. The sensor wears in the spot that it spends the most time, idling. The engine can’t maintain idle speed if it can’t sense the throttle position.
As stated, there are many potential causes. However, I have replaced a few Taurus TPS for this.
I had a stalling problem in a 05 Ford E150 with 160.000 miles, It turned out to be a bad Idle control valve
Just my 02 cents
Ford code P1633 “Keep Alive Power Voltage Too Low”.
I’d say your alternator has passed ‘going’ out and is now gone.
Keep alive power too low would be a battery issue me thinks. The keep alive power is what maintains the memory in the ECMs when the engine is off.
Of course it could be the result of a bad alternator, but a battery test is in order for sure (along with a test of the alt)
If the ECM lost its memory that by itself could explain the lack of idle, or it could be other issues.
Yeah, trouble codes are just an indicator of where to look for the problem. But at least the indication is for a voltage issue. And the previous owner may only think that the alternator is going .
It could be some other voltage related problem.
Check the PCV hose(s) behind/under the throttle body. They tend to weaken/develop holes and leak, causing significant idle quality issues. This is ten to a hundred times more common on this engine than any of the other items mentioned.
We were having the same problem with a 2003 Honda Element. It got noticable worse in colder weather. Replacing the spark plugs took care of it.
Okay.
I fired it up, drove it to the shop by means of shifting into neutral and revving it to 1600 RPM when I had to stop at lights.
The shop is about two miles away.
One quarter of a mile from the shop, I heard a sound like a gunshot from under the hood.
The dash suggested I check the charging system at this point, and the battery light came on.
I still made it to the shop, although of course the power steering wasn’t working.
If I understand the situation properly, I made it 1/4 of a mile with no alternator, and the spark plugs being driven purely by the battery.
I’ve uploaded pictures of what I saw under the hood, as well as the final bill with my real name obscured.
Thanks for the tips!
So, the AC compressor went out, locked up, and caused the serpentine belt to go ‘blewie’, is that it?
‘Blewie’ is a technical term not specific to Fords.
Yeah, and I got the chance to drive a gas car with the battery not getting charged.
Awesome!