2000 mustang runs rough and dies when warm

RandyBobandy · Jun 18, 2019

Hello everyone, I just got my first mustang and I’m having a few issues, it’s a 2000 v6 5 speed.

On a cold start it runs and drives great, but after it warms up it idles rough and actually died on me yesterday and didn’t want to restart, after letting it sit for a while it started fine and ran fine

The codes I’m getting are p0411 for the secondary air pump, as well as lean codes for both banks and a misfire on cylinder 4. It is definitely missing at idle when warm but not on a cold start and it usually smooths out at a higher rpm

Any idea what could be causing this? I get the idea from the research I’ve already done that the p0141 secondary air pump code might me a separate issue. Could a bad ignition coil cause these symptoms?

Any help is appreciated, thanks

Noobz347 · Jun 18, 2019

My first guess:

You need a new fuel pump.

Either check the fuel pressure at the rails when this occurs (to verify my assessment) or just go out and get the thing changed.

RandyBobandy · Jun 18, 2019

Thanks a lot, how hard is the fuel pump to change? I’ve done fuel pumps before but only on Toyota’s, do I need to drop the tank or is there an access port?

I will test the fuel pressure later tonight and update with my results

Noobz347 · Jun 18, 2019

RandyBobandy said:
Thanks a lot, how hard is the fuel pump to change? I’ve done fuel pumps before but only on Toyota’s, do I need to drop the tank or is there an access port?

I will test the fuel pressure later tonight and update with my results

You will have to drop the tank. It's not tough. If you have a full tank, you can disconnect at the fuel rail (you will need a tool for this) and pump into gas cans (an extra couple feet of flexible fuel line helps a lot).

Remove the straps, drop the tank keeping an eye on the donut for the tank fill line (get a new one of these and have it on had to be safe, LMR has them) and any vent lines and wires. You can use a floor jack to lower the tank once the back of the car is on stands.

Inspect your tank straps before removal to see if they will need to be replaced.

An extra long bolt the same thread pitch as the tank strap bolts can be very useful for putting it all back together.

Make sure the new pump comes with all the 'stuff'. New o-ring for the tank, sock, connectors, and whatever else I'm forgetting.

I jsut wasted many letterz

Here's a 6 1/2 minute video

View: https://www.youtube.com/watch?v=SOmd3BoE4YU

RandyBobandy · Jun 18, 2019

That looks easy enough, I’ve dropped a tank before but never on a car this low. Is it common for these pumps to show issues only once the car has warmed up? On my Toyota’s the pumps always just failed suddenly.

The previous owner told me he had been having a rough idle issue for a few months but it never died on him, it just died when I got it

Thanks for all the help, I really appreciate it

Noobz347 · Jun 18, 2019

RandyBobandy said:
That looks easy enough, I’ve dropped a tank before but never on a car this low. Is it common for these pumps to show issues only once the car has warmed up? On my Toyota’s the pumps always just failed suddenly.

The previous owner told me he had been having a rough idle issue for a few months but it never died on him, it just died when I got it

Thanks for all the help, I really appreciate it

Is it common? Not really, but your symptoms are the example for when it happens (and often the source for the 'Found On Road Dead' moniker).

I have to remember to keep your fuel system different from mine in my head. You guys have the returnless system. A bad fuel pressure regulator can cause this issue as well but it is most likely the pump. Furthermore, if you have no idea how many miles are on that pump or if it is original, then it needs to be replaced anyway.

RandyBobandy · Jun 18, 2019

Are these cars picky on what brand of fuel pump I get? Would the delphi pump from rock auto work or should I go with oem?

If the pump fixes it this will be my third vehicle with an uncommon fuel pump failure

Noobz347 · Jun 18, 2019

RandyBobandy said:
Are these cars picky on what brand of fuel pump I get? Would the delphi pump from rock auto work or should I go with oem?

If the pump fixes it this will be my third vehicle with an uncommon fuel pump failure

I would get an OEM pump unless you know the manufacturer is the same.

As far as seeing this uncommon failure often well... It happens to people who buy and ride used cars. LoL

I had a Taurus SHO once that made for some great stories. I bought it from a member here many years ago and it continually tried to kill me until I sold it.

RandyBobandy · Jun 18, 2019

Do you know what brand name the oem pump is? Is it motorcraft?

RandyBobandy · Jun 18, 2019

Ok I just did a pressure test, got 20 psi on a cold start, 900rpm idle. Pretty much no change when I revved it up to 2500 rpm, then it stumbled and died, and restarted fine

If you confirm this is abnormal pressure I’ll go ahead and order the pump and update after that

RandyBobandy · Jun 21, 2019

Just wanted to update, I got a new fuel pump in and it fixed my issue. The filters on the old pump were extremely dirty

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