Help diagnose intermittent 2005 Mustang GT throttle problem.

[zanemoseley]

My wife has a 2005 Mustang GT with 125k miles. She's had occasional throttle problems over the last couple years. A couple years back she was having a low idle and stalling at stops, I fixed this by cleaning the TB and replacing the K&N with a standard air filter as I read the oil coating on the K&N drop in's can cause this issue. She has also had occasional sudden drops in power, this is solved by pulling over and turning off the car and restarting when resets the computers and sensors.

Yesterday she had one of the worst episodes yet. First thing in the morning she had 7 times in a row where the car stalled or completely lost power and went into "limp mode". It would reset and act normal for a brief period if she restarted the car. She said the "wrench light" was on which from what I've read indicates an issue with the TB. After the both of us reading some I felt confident enough it was the TB and went ahead and ordered a Ford Racing TB from American Muscle for $200. The car drove fine for the remainder of the day.

We swapped cars today and I drove the mustang as she has a lot more driving to do and didn't want to risk having problems. First thing I noticed when I got in the car was the check engine light was on (not the wrench light), she said this was not on yesterday. The car drove well the entire day and after work I went and got the codes read and it was as follows:

P0193: Fuel Rail Pressure Sensor had high voltage input for a predetermined period of time. It recommended replacing the Fuel Rail Pressure Sensor.

So now I'm confused a bit. Did the TB issues cause this code to be triggered? What I don't wanna do is install the new $200 TB only to have it be the Fuel Rail Pressure Sensor. My reading indicated that the wrench light is specific to TB issues.

So what do I do?

 

[master_shake_]

do you have access to a scan tool?

a frps voltage at idle and wot could help you out.

you can use a voltmeter as well.

just find the wire in the plug that has a lower voltage than 5 and a higher voltage that zero at idle.

there's only 3 wires.

 

[zanemoseley]

I don't have a scanner tool. Honestly you're over my head. Is the plug you speaking of the diagnostic plug under the steering wheel where they read the codes.

Sent from my VS985 4G using Tapatalk

 

[Quiksilver]

My wife has a 2005 Mustang GT with 125k miles. She's had occasional throttle problems over the last couple years. A couple years back she was having a low idle and stalling at stops, I fixed this by cleaning the TB and replacing the K&N with a standard air filter as I read the oil coating on the K&N drop in's can cause this issue. She has also had occasional sudden drops in power, this is solved by pulling over and turning off the car and restarting when resets the computers and sensors.

Yesterday she had one of the worst episodes yet. First thing in the morning she had 7 times in a row where the car stalled or completely lost power and went into "limp mode". It would reset and act normal for a brief period if she restarted the car. She said the "wrench light" was on which from what I've read indicates an issue with the TB. After the both of us reading some I felt confident enough it was the TB and went ahead and ordered a Ford Racing TB from American Muscle for $200. The car drove fine for the remainder of the day.

We swapped cars today and I drove the mustang as she has a lot more driving to do and didn't want to risk having problems. First thing I noticed when I got in the car was the check engine light was on (not the wrench light), she said this was not on yesterday. The car drove well the entire day and after work I went and got the codes read and it was as follows:

P0193: Fuel Rail Pressure Sensor had high voltage input for a predetermined period of time. It recommended replacing the Fuel Rail Pressure Sensor.

So now I'm confused a bit. Did the TB issues cause this code to be triggered? What I don't wanna do is install the new $200 TB only to have it be the Fuel Rail Pressure Sensor. My reading indicated that the wrench light is specific to TB issues.

So what do I do?

Have you tired cleaning the MAF sensor? I mean if doing all this throttle body work has helped you in the past, I'd be curious if the MAF sensor is functioning correctly.

I'm not familiar with your car but I'm curious if you car has flood clear mode too.

As your ETBC is controlled by a separate module than your fuel pressure sensor, the throttle body issue is highly unlikely the reason you have this code.

What that code means is that it detected a higher than normal voltage for a set period of time. So if Ford in this case had programmed it to say 5V is the maximum voltage threshold to be detected for a maximum of 2 seconds, and the ECU detects it was at 6V for 3 seconds it will throw that code.

Which case, I would located that sensor under the hood ( my guess its on the drivers side bank somewhere.) unplug it, double check to make sure there no build up in the connections and plug it back in making sure its secure before its assuming its bad.

I'd also say it could be possible all the constant restarting, and resetting from going into limp mode then back. I'd say the code could be from all that too. It would be hard to say without taking a scanner to it and looking at the data.

I don't have a scanner tool. Honestly you're over my head. Is the plug you speaking of the diagnostic plug under the steering wheel where they read the codes.

Sent from my VS985 4G using Tapatalk

No, he referring to the fuel pressure sensor under the hood. It has three wires, usually ground, 5V reference, and 12V power.

In all honestly, I feel you need to take this car to a reliable mechanic before you throw any more money at this vehicle. Combine that with the fact is you may have more codes than you realize as there are codes triggered that don't throw the money light and if you have multiples of those related to the same issue, it could indicate what is wrong but you'll never know about those without a scanner. No need to start swapping parts without knowing if that is the issue or not.

 

[master_shake_]

I don't have a scanner tool. Honestly you're over my head. Is the plug you speaking of the diagnostic plug under the steering wheel where they read the codes.

Sent from my VS985 4G using Tapatalk

i was talking about the plug on the fuel rail pressure sensor.

under the hood

 

[boomerang]

Have you tired cleaning the MAF sensor? I mean if doing all this throttle body work has helped you in the past, I'd be curious if the MAF sensor is functioning correctly.

This. Especially when using a K&N filter.

 

[Quiksilver]

Have you tired cleaning the MAF sensor? I mean if doing all this throttle body work has helped you in the past, I'd be curious if the MAF sensor is functioning correctly.

I wanted to quote myself here just to further elaborate.
The MAF or mass air flow sensors job is to detect/measure how much air flow is entering into the engine (more specific intake manifold) so the ECU can adjust fuel trims accordingly to maintain a balance between air/fuel delivery to achieve good combustion.

So what exactly happens when it becomes dirty or malfunctions? The fuel trims either become too rich or too lean and the result it often stalling (too lean) or poor fuel economy (too rich) for the amount of air actually being sucked into the engine. (not saying there aren't other symptoms but I feel these would be the most evident of an issue.)

Which would be why I am curious if the sensor if functioning correctly, I feel like your 'stang is on the lean side of things but not enough to cause fuel trim codes but just enough to cause problems,

 

[Raizinman]

I fixed this by cleaning the TB and replacing the K&N with a standard air filter as I read the oil coating on the K&N drop in's can cause this issue.

Well, the best thing you did was getting rid of the K&N air filter. They do not increase horsepower and do not give you better gas mileage. Heck, if they did, all the car manufacturers would be using them, but we see not even one manufacturer using them. Besides that, they allow too much dirt to pass through the filter. They also cause all sorts of long term problems especially with MAF sensors as you are now finding out. Same thing for CAI (Cold Air Intakes), yes, they look Kool and allow the driver to hear more engine noise, but again, no HP increase. It is just a gimmick that makes you think you have more HP because your ears hear more engine noise.

 

[drnickriviera]

Sounds similar to my 05' F-150. Driving along and then the pedal does nothing, engine went to idle and limp mode turned on.. Turned the engine off and on and it worked fine. It was the electronic throttle body. I had no other codes though.