[dabadee]

while driving, my car dies when i push in the clutch. it started when i changed from 93 to 87 octane gas. have the sct x3 and changed the tune when i switched gas. idles kind of rough at startup but dies when the rpms slam down from a shift point or when stopping. any advice would be helpful. im 800 miles from home on vacation. im at my destination for a bout a week so i have a little time to work on it.

 

[dabadee]

also throw trouble code 1290

 

[stlwagon]

Sounds like you have a failing cylinder head temp sensor.

 

[dabadee]

would this cause the rough idle and stalling

 

[stlwagon]

would this cause the rough idle and stalling

You bet... If the car isn't sensing it's reached operating temperature, it's probably not coming out of open loop and dumping too much gas into the engine. Do you smell a very strong exhaust lately?

 

[dabadee]

no but this has started today. never had this kind of issue till now. also got good gas mileage and still makes good power just when the rpms go from traveling speed to idle does it die

 

[dabadee]

also worse when the ac is on. dont know if this makes a difference

 

[stlwagon]

I'd reintall the other tune and see what happens.

 

[dabadee]

done that does it with both tunes. tried raising the neutral idle rpm that seems to help with the rough idle will have to take it for a spin to see if it helps with the comming to a stop problem

 

[stlwagon]

Sounds like that sensor is going to need to be replaced.

 

[dabadee]

any idea where it is located

 

[stlwagon]

any idea where it is located

It's under the intake plenum on the passenger side of the engine.

 

[stlwagon]

Here's a picture.

 

[chp2150]

Yeah, that's convenient to get to while on vacation! "Honey, I'll be in the parking lot of the hotel field stripping the Mustang, go ahead and take the kids to the pool".

Sorry it picked this trip to crap out on you.:frustrated:

 

[travelers]

done that does it with both tunes. tried raising the neutral idle rpm that seems to help with the rough idle will have to take it for a spin to see if it helps with the comming to a stop problem

Neutral idle if for autos not sticks.

 

[ski]

For reference, the PCM normally has to re-learn the idle strategy after a tune is either replaced or reinstalled, or the battery is either disconnected or replaced, all of which can cause idle problems. There is a procedure in the battery section of the owner's manual that is supposed to help the PCM re-learn the idle strategy quicker.
However, in your case it appears that the cyl. head temp sensor trouble code is pointing to the cause of your car's idle problem, as stated by others.

 

[stlwagon]

Neutral idle if for autos not sticks.

No, idle neutral is only for stick. Idle drive is for autos only.

 

[dabadee]

raised idle rpm. went into failsafe mode about 1/4 mile down the road. needless to say turned right around. is this a dealer item or something i can pick up from autozone

 

[stlwagon]

raised idle rpm. went into failsafe mode about 1/4 mile down the road. needless to say turned right around. is this a dealer item or something i can pick up from autozone

That is a dealer part. There are two possible part numbers depending on where your engine was built.
Romeo Tag# 5S690, 5S691 -- 4L3Z12A648AB
Windsor Tag# 5S836, 5S837 -- F5AZ12A648AB

 

[stlwagon]

Disregard... That's for the coolant temp sensor. The engine temp (cyl head) sensor is p/n 3L7Z6G004BA