Engine 2001 Gt 4.6 Idle Rough And Will Not Stay Running

RlovellGT · Feb 15, 2015

Hi all,
As the title states, I have a 2001 Mustang GT, 4.6, just purchased (not running) and it looks mostly stock except some model of BBK Cold Air Intake and not sure what else.

Symptoms-at first it was very hard to start, and when it did , it would not stay running. If I keep pushing on the throttle it will run, but not clean. It sounds like it is trying to die. If I let off throttle it will sputter and die. I got it to run for about 2 seconds then die again
Possible solutions already tried-
Emptied fuel tank, brand new gas in it, replaced fuel filter. Transmission fluid down the cylinders to try to build compression.
cleaned IAC with carb cleaner, reset battery
Current status- After this is when I got it started fully finally, still had to pump the throttle but it was at least started. It is still dying after start, IF it does start.
It appears fuel is coming out of the throttle body/carburetor area, like its flooding itself out which appears to be causing it to die.

Can anyone recommend any troubleshooting things or what might be causing the car to flood, and fuel in the carburetor?

I tried to be as clear as possible. Any questions please message me or post and I'll be glad to talk.

Need some serious help to get this car to start right and stay running or idle right.
Thanks in advance.

vertigasen · Feb 16, 2015

Ok, this does not have a carburetor, it is fuel injected. The fuel is injected into the intake manifold where the intake runner meets the cylinder head. If there is fuel coming out of the throttle body, there is a HUGE problem because that is no where near where it is sprayed by the injectors. If there is fuel near the throttle body, you need to look and see if there is a fuel leak spraying fuel up there.

What codes are being thrown? What is the fuel pressure (actual rail pressure)? Have you cleaned the MAF?

RlovellGT · Feb 16, 2015

vertigasen said:
Ok, this does not have a carburetor, it is fuel injected. The fuel is injected into the intake manifold where the intake runner meets the cylinder head. If there is fuel coming out of the throttle body, there is a HUGE problem because that is no where near where it is sprayed by the injectors. If there is fuel near the throttle body, you need to look and see if there is a fuel leak spraying fuel up there.

What codes are being thrown? What is the fuel pressure (actual rail pressure)? Have you cleaned the MAF?

No codes are being thrown at all.
How can I dertermine what the fuel pressure is?
Next step is to clean the MAF
I will start trying to figure out where the fuel is coming from..

Thanks for help

squeak93 · Feb 16, 2015

Do a compression and leak down test before going any further.

RlovellGT · Feb 16, 2015

Do I have to have those done at the dealer? Or how can I accomplish those test?
Thanks!

madspeed · Feb 16, 2015

could be a bad or leaky fuel pressure reglator. Sounds as though you need someone with some mechanical ability to look at it, as you seem very green

RlovellGT · Feb 16, 2015

Well I am green, that's why I am here..

But I have a mechanic working with me, I just said the wrong thing..

Chill...

vertigasen · Feb 16, 2015

Dude, don't worry about it. We will help all we can......

1) You have a returnless fuel system, so you don't have a fuel pressure regulator. That is why I said check the fuel pressure, you could have a bad PPRV (positive pressure relief valve) in the fuel tank. It prevents pressure from backing off the fuel lines so that it is easier to start, and the system doesn't have to re-prime every time. The fuel pump could be having issues. You should have a Schrader valve on the front passenger side of your fuel rail (kinda looks like an air valve). You can get a basic fuel pressure gauge at any auto parts store, remove the shrader valve, and thread the gauge on. Just turning the key on, it should go to 45psi and hold. If it goes to 45, then drops off, that could be the PPRV. If it doesn't make it to 45, it could be the pump. You don't even have to try to start it to see this.

A compression test is easy to do. Most parts stores will have a compression test kit. To test, remove the spark plug and put the tester in the spark plug hole. I usually remove all the plugs and do them back to back. IMPORTANT, remove the plug from all the injectors so that they do not fire or it will blow fuel everywhere. Did that once...lol.

For a leakdown test, you need another tool (sometimes packaged with the compression tester to make life easier). This time, you use an air compressor to put compressed air into the cylinder. You make sure that the valve are in a closed position, and inset air.

Also, go get a Chiltons and/or Haynes guide. I have both, and refer to both. They say the same things, just in slightly different ways. They will show you how to do these tests.

What is odd is that it runs rough when it does start, but does not throw a Check Engine Light.

RlovellGT · Feb 16, 2015

vertigasen said:
Dude, don't worry about it. We will help all we can......

1) You have a returnless fuel system, so you don't have a fuel pressure regulator. That is why I said check the fuel pressure, you could have a bad PPRV (positive pressure relief valve) in the fuel tank. It prevents pressure from backing off the fuel lines so that it is easier to start, and the system doesn't have to re-prime every time. The fuel pump could be having issues. You should have a Schrader valve on the front passenger side of your fuel rail (kinda looks like an air valve). You can get a basic fuel pressure gauge at any auto parts store, remove the shrader valve, and thread the gauge on. Just turning the key on, it should go to 45psi and hold. If it goes to 45, then drops off, that could be the PPRV. If it doesn't make it to 45, it could be the pump. You don't even have to try to start it to see this.

A compression test is easy to do. Most parts stores will have a compression test kit. To test, remove the spark plug and put the tester in the spark plug hole. I usually remove all the plugs and do them back to back. IMPORTANT, remove the plug from all the injectors so that they do not fire or it will blow fuel everywhere. Did that once...lol.

For a leakdown test, you need another tool (sometimes packaged with the compression tester to make life easier). This time, you use an air compressor to put compressed air into the cylinder. You make sure that the valve are in a closed position, and inset air.

Also, go get a Chiltons and/or Haynes guide. I have both, and refer to both. They say the same things, just in slightly different ways. They will show you how to do these tests.

What is odd is that it runs rough when it does start, but does not throw a Check Engine Light.

Thanks! We are iced in, in Arkansas so as soon as it thaws I will be renting a compression tool and fuel pressure test tool as well.

I have chiltons book I purchased as well. Thanks for the info I will report back once tests are performed.

vertigasen · Feb 16, 2015

Good luck! We were all "green" at one point, but we had to learn somewhere.

RlovellGT · Feb 17, 2015

Yeah I am trying my best, I am not a mechanic..obviously..

Got a battery test-good
Alternator-bad going to replace

Got a quick question though, on the schrader valve, if I push in the pin, shouldn't fuel be coming out? If so, it's not..

I have the compression test kit, and fuel pressure kit we are going to try I was just curious if any fuel should be coming out of the valve before we test it..

RlovellGT · Feb 17, 2015

RlovellGT said:
Yeah I am trying my best, I am not a mechanic..obviously..

Got a battery test-good
Alternator-bad going to replace

Got a quick question though, on the schrader valve, if I push in the pin, shouldn't fuel be coming out? If so, it's not..

I have the compression test kit, and fuel pressure kit we are going to try I was just curious if any fuel should be coming out of the valve before we test it..

UPDATE-when putting the fuel pressure kit on the schrader valve we are getting ZERO PSI output.

What does that point towards and what might be next to try?

vertigasen · Feb 17, 2015

Check the roll over switch in the trunk, the fuses for the fuel pump related items (F1.14, F2.32, and F1.26), and the power to the FPDM.

Any of those could be the issue. If those check out, and you are getting power past the FPDM, then you need to check the pump. Drop the tank, and add power directly through the harness to see if it turns on.

good luck!

RlovellGT · Feb 17, 2015

Yessir just read about the switch shortly after I posted, was going to check that tomorrow. Will check fuses and pump and see what happens and report back. Thanks again..I'll let you know!

JLB3 · Feb 17, 2015

My v6 triggered the switch one day randomly too. Hope that's all it is for you.

RlovellGT · Feb 18, 2015

Everything checked out it seemed all the way to the fuel pump.

Checked fuel pump and at first key turn we had under 10 lbs pressure, everytime after that it built more pressure all the way to between 40-50 psi.

Although after we turned ignition off the pressure dropped continuously down to 35 in 30-45 seconds.

Is this normal? Does that sound Ike a fuel pump? Any other suggestions? What I don't get is why does it seem like it's flooding out, almost seems like too much fuel?

Also gas still coming out of here: attached picture..

RlovellGT · Feb 18, 2015

Also this clip appears to not be attachIng properly see zip ties, what is this and what would I need to replace? The entire harness or is that part of the fuel pump?

vertigasen · Feb 18, 2015

The pressure building up with the ignition on is good. The pressure will drop off some , but it shouldn't just drop quickly to 0. If you try to start it, the pressure will probably go up a little more, until it starts. The PPRV in the fuel tank will keep some of the pressure on, so that when you turn on the ignition, it doesn't have to re-prime. So that is fine.

Gas coming out of the throttle body is BAD. I have actually never seen that before.

You are trying to start it with the intake on right? The air going into the engine must be metered by the MAF. If not, it is just like having a vacuum leak, unmetered air is entering the engine and the ecu is not adding enough, or adding too much fuel.

jetmech807 · Feb 18, 2015

This sounds like a massive vacuum leak. My BBK cold air kit has a hole with a plug in it to insert a Nitrous nozzle. Check yours and make sure that hole is plugged. If you need a pic let me know.

RlovellGT · Feb 18, 2015

Ok I'll check those last time we had the CAI on it wouldn't start..
Should I take the MAF sensor off and clean it to test?
One thing that is throwing me is why is there no fuel at the schrader valve? Shouldn't there be?

Engine 2001 Gt 4.6 Idle Rough And Will Not Stay Running

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