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Rough Idle and flashing battery light

Tiny
JOSEPHG548
  • MEMBER
  • 2004 FORD CROWN VICTORIA
  • 4.6L
  • V8
  • 2WD
  • AUTOMATIC
  • 149,800 MILES
My car recently started having a really rough idle so when I did an oil change, I also put in a new alternator along with spark plugs and coils, but the issue is still there. The idle is super rough and the battery light flashes. All components such as the A/C and radio are working fine and when I got my battery checked they are saying it is still good.
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Saturday, May 28th, 2022 AT 4:27 PM

16 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,896 POSTS
Hi,

We need to determine if power from the alternator is making its way to the battery. Also, there needs to be battery voltage at the alternator also.

Try this test and let me know the results. All you will need is a voltmeter or multimeter.

https://www.2carpros.com/articles/how-to-check-a-car-alternator

If you are not getting a charge, go to the alternator. There will be a black wire with an orange tracer. That wire should have 12v at all times. Confirm that is the case.

Let me know what you find or if you have other questions.

Take care,

Joe

See pics below.
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Saturday, May 28th, 2022 AT 10:52 PM
Tiny
JOSEPHG548
  • MEMBER
  • 13 POSTS
Hey! I went ahead and tested, with the car off its reading 12.66 and with the car on with A/C and radio on it is reading 14.35. Just to be sure I also tested the black wire to the alternator, and it does have 12 Vs going to it with the car off.
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Sunday, May 29th, 2022 AT 7:46 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,896 POSTS
That sounds perfect. Was the battery light flashing when it was being tested? If so, there could be a wiring issue at the PCM (powertrain control module). Just for curiosity, does the light flash only at low RPMs or does it also flash while driving?

Is the check engine light staying on when the engine is running? If so, have you had the computer scanned for codes? Most parts stores will do it free of charge.

I have one last request. Is it possible to record it running and upload it for me to hear?

Let me know.

Joe
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Sunday, May 29th, 2022 AT 7:38 PM
Tiny
JOSEPHG548
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  • 13 POSTS
The battery light wasn’t flashing while being tested. It only flashes during low RPMs, never while driving but if I’m stopped at a light or stop sign the RPMs fluctuate and it flashes on and off. When I bought the car the check engine lights are on due to no O2 sensors because they cut the muffler and cats off along with a shift and torque solenoid, but it ran good just a bit slow with shifting to the point those aren’t an immediate concern and already have the replacement solenoids, just need the free time. I had them run codes, O2 sensors came up as expected along with the solenoid but I also had P0446, P0443 and P1747 show up which to my knowledge is new as my code reader can’t access the car. The long video attached is it starting up and the next one is after I got back from getting the codes read but it wanted to pretend to be okay then.
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Monday, May 30th, 2022 AT 10:20 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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When the light is flashing, how low do the RPM's get?

Joe
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Monday, May 30th, 2022 AT 7:02 PM
Tiny
JOSEPHG548
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  • 13 POSTS
I can’t be exact since there is no Tachometer gauge, but I’d have to guess it will go down to 500, and even lower on some occasion right before stalling out which happens but not very often.
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Monday, May 30th, 2022 AT 7:40 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

If it is getting that low, that could be the reason the charging light is turning on and off. Two of the new codes are related to the evaporative emissions system which could be causing the rough and low idle. That could result in the battery light flashing if it is idling low enough. One is regarding the canister vent solenoid and the other is the canister purge solenoid.

When you put fuel in the tank, have you ever had difficulty where the pump turns off, or have you ever noticed a fuel smell when the vehicle sits idle, parked and off, or after adding fuel?

If not, then we need to check the purge

Now, the P1747 isn't listed as a possibility for this specific vehicle. I know it deals with transmission pressure control solenoid issue. I don't feel this is the cause.

If you look at pic 1 below, it describes each of the new codes and possible causes. So, what I suggest is this. The solenoids are both electric. We need to check the wiring and connectors to them.

The canister and canister vent solenoid are located under the vehicle near the fuel tank. Starting with pic 2, I provided the directions for the removal and installation. Remove it and inspect the wiring and hoses to it.

The purge solenoid is located under the hood (I believe on the driver's side. I attached a pic of it below. Do the same thing with this. See the last pic.

Let me know what you find.

Joe

See pics below.
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Monday, May 30th, 2022 AT 8:14 PM
Tiny
JOSEPHG548
  • MEMBER
  • 13 POSTS
The wires looked good along with the connectors on the end, but the vent solenoid and purge solenoid were all beat up looking and for sure have to be factory. I went ahead and replaced both of those, the issue is less worse, check engine light is now gone which is nice to see and it drives pretty good but once I’m in the driveway which is on an incline since I’m in SWFL, it goes back to bad. I attached a video starting in drive with foot on the break along with e-brake engaged with the battery light flashing then I put it into park and it’s firing gets better but not 100%.
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Tuesday, May 31st, 2022 AT 11:07 AM
Tiny
JOSEPHG548
  • MEMBER
  • 13 POSTS
Little update, a buddy came over and I wanted to show him how it was doing, and check engine light is back and after about a minute or so of running it was back to running quite rough, still on the incline.
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Tuesday, May 31st, 2022 AT 12:51 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,896 POSTS
Listening to the idle, it sounds extremely low. Are the same codes back? If they are, we need to smoke test the EVAP system to see if there is a leak.

Basically, smoke is introduced via a port on the vehicle's EVAP system. If there is a leak, the smoke will leak at that point.

I may have asked already, but does your scanner provide live data? If there is a big enough vacuum leak via the EVAP system, it would be getting unmetered air causing a lean fuel mixture. Also, I noticed that the exhaust is either leaking or has been modified. If it is leaking, is it before the catalytic converters?

Also, check to see if there are any engine vacuum leaks. Here is a link that explains how it's done:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let me know.

Joe
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Tuesday, May 31st, 2022 AT 8:45 PM
Tiny
JOSEPHG548
  • MEMBER
  • 13 POSTS
I just started a new apprenticeship, so my free time is limited and sadly my code reader isn’t advanced enough to get any of the codes. So, it’ll be a while before I get it up to a shop to see. When I bought it, the previous owner had cut off the cats and rewelded the pipe back on before also cutting out the mufflers. Once I get a chance, I will get those codes ran and will have them run a smoke test. Thank you for the help and I will hopefully be able to get it up to a shop on Saturday and will update you then!
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Wednesday, June 1st, 2022 AT 7:19 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,896 POSTS
Hi,

No problem whatsoever. Let me know whenever you get the chance. I will tell you that the catalytic converters being removed are going to have an effect on how it runs. The PCM uses signals from the oxygen sensors to adjust the air/fuel mixture. If they have been removed, the PCM doesn't know how to set things.

Let me know. I'll watch for your reply.

Take care,

Joe
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Wednesday, June 1st, 2022 AT 9:02 PM
Tiny
JOSEPHG548
  • MEMBER
  • 13 POSTS
Hey Joe! I finally had the time to get it in, they said there is a small vacuum leak somewhere but didn’t do anything for it and also replaced my Mass Airflow Sensor which has it running nice and smooth again but now I’ve run into a new issue. My battery doesn’t seem to charge even though I have a new alternator and just got a new battery. All connections look good, and my belt is good as well. I’m not sure what it could be, could it have something to do with the new coils?
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Thursday, June 16th, 2022 AT 5:43 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,896 POSTS
Hi,

I want you to try a simple test to see what the alternator is producing. All you will need is a voltmeter or multimeter. Follow the directions in this link and let me know the results:

https://www.2carpros.com/articles/how-to-check-a-car-alternator

I believe I listed that link before, but I can't remember. LOL, I will watch for your reply.

Take care,

Joe
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Thursday, June 16th, 2022 AT 10:08 PM
Tiny
JOSEPHG548
  • MEMBER
  • 13 POSTS
I checked and after starting it here and there to keep fluids moving the battery starts at 11.7 and will dip down as low as 11.5 but will go up when something disengages. I think it’s the A/C, but when it engages it drops right back down. I took the alternator off and everything on it and the connectors seems to check out.
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Thursday, June 23rd, 2022 AT 4:34 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,896 POSTS
Hi,

The alternator isn't charging. It should be around 14v with the engine running. If you rev the engine when testing, does it increase to approximately 14v?

If you, have it off, take it to a parts store and have them bench test it. Most parts stores will do this free of charge.

Let me know what you find.

Joe
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Thursday, June 23rd, 2022 AT 8:58 PM

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