Idle drops and drops till it dies

[A John In NJ]

Hello all,

So I got the P0340 DTC, Cam sensor, and from what I read its because of the alternator. Ok So I changed the alternator to a PA alternator and the bigger gauge wire. I then returned the ecu back to stock and then reloaded the a strategy tune (Since I dont have a custom tune yet). The only adjustments I made are the axle ratio and neutral idle (870).

I turned the car over and it idles normally for about a min then it slowly drops under 750 with a weak semi rough idle and the car shakes a bit and the lights dim. It continues to drop very slowly till it eventually shuts off.

the only mod I have is the JLT 3, which I put in the strategy tune.

Any ideas?

 

[stkjock]

Check your grounds?

 

[BruceH]

Hello all,

So I got the P0340 DTC, Cam sensor, and from what I read its because of the alternator. Ok So I changed the alternator to a PA alternator and the bigger gauge wire. I then returned the ecu back to stock and then reloaded the a strategy tune (Since I dont have a custom tune yet). The only adjustments I made are the axle ratio and neutral idle (870).

I turned the car over and it idles normally for about a min then it slowly drops under 750 with a weak semi rough idle and the car shakes a bit and the lights dim. It continues to drop very slowly till it eventually shuts off.

the only mod I have is the JLT 3, which I put in the strategy tune.

Any ideas?

Did you plug the maf back in?

 

[A John In NJ]

Yup, All good there

I dont get how after a min the idle starts to slowly drop.

Will running the car without the cam sensor connector plugged in damage the cams or the engine itself? The car was on idle only while the plug was off

 

[A John In NJ]

Did you plug the maf back in?

Yes sir

 

[RocketcarX]

Almost sounds like it's running out of fuel. Is the fuel pump remaining on the entire time?

 

[BruceH]

Are all of the vacuum lines hooked back up?

 

[Speed+Clinic]

It's electrical because of the lights dimming. (unplugged MAF, lines, fuel wont cause the interior lights to dim if you are good on the battery.) You could have gotten a bad battery or alternator. Is the alternator connected properly? Did you check all leads? Start the car up and and remove the battery while its on. What does it do?

 

[RocketcarX]

Are the lights just dimming out or are they just dimming from super low RPMS and no alternator voltage? If they are dimming out and the car still restarts on it's own that is def an odd one. What is the voltage doing at the battery while this happens?

Are all of the vacuum lines hooked back up?

vacuum leak sounds pretty reasonable too

 

[joe_momma]

Sounds like a vacuum/air leak. Similar thing would happen to me when my CAI came loose.

 

[A John In NJ]

I will check all of these things when I get home today.

Are the lights just dimming out or are they just dimming from super low RPMS and no alternator voltage? If they are dimming out and the car still restarts on it's own that is def an odd one. What is the voltage doing at the battery while this happens?

As the cars idle drops so do the lights. As soon as I give it some throttle then the idle jumps back to 1K and after a min it begins to repeat the idle drop.

Could it be in the tune cause the JLT is the 3 series? I didnt see that in the "Strategy Tune" settings. They just have JLT ( Im assuming its the series 2, Smaller CAI)?

 

[01yellerCobra]

It's electrical because of the lights dimming. (unplugged MAF, lines, fuel wont cause the interior lights to dim if you are good on the battery.) You could have gotten a bad battery or alternator. Is the alternator connected properly? Did you check all leads? Start the car up and and remove the battery while its on. What does it do?

That's not advised anymore. The shock from disconnecting/reconnecting the battery can fry the ECU.

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[Department Of Boost]

Sounds like an alternator issue (yes, new alternators can be bad, especially 6G's) that is not being helped by a weak battery.

 

[A John In NJ]

I took the car out to see what would happen and the results are:

The CEL came out code P0174 ( System too lean) WTF!

After driving for a short period, When I stopped at the light the idle dropped to slightly under 500rpm and then it dies.... It happened at every stop sign and red light.

I checked all the hoses, MAF, Alternator and all lines.

Im lost... This poor car has gone through a lot

 

[A John In NJ]

Sounds like an alternator issue (yes, new alternators can be bad, especially 6G's) that is not being helped by a weak battery.

How can I know for sure its the alternator?

 

[Department Of Boost]

How can I know for sure its the alternator?

I said:

“Sounds like an alternator issue (yes, new alternators can be bad, especially 6G's) that is not being helped by a weak battery.”

I did not say it is.

Big difference.

And here is a fun fact for you. When the voltage in the system drops below a certain level the ECU starts freaking out and randomly throws codes. The Ford ECU’s are not the only ones that do this.

Do you have a volt meter? You have some testing to do.

 

[BruceH]

Do you have another cai you can put on? The JLT 3 is significantly larger than the 2 and if your canned tune is using the maf transfer function for the 2 (you weren't sure) it would give pretty much the same symptoms as a vacuum leak.

It starts and idles for awhile when cold, correct? That would be open loop which doesn't rely on the maf signal for proper fueling. If I'm understanding your symptoms correctly it's during closed loop that the problems start.

 

[A John In NJ]

Do you have another cai you can put on? The JLT 3 is significantly larger than the 2 and if your canned tune is using the maf transfer function for the 2 (you weren't sure) it would give pretty much the same symptoms as a vacuum leak.

It starts and idles for awhile when cold, correct? That would be open loop which doesn't rely on the maf signal for proper fueling. If I'm understanding your symptoms correctly it's during closed loop that the problems start.

You are 100% correct

 

[RocketcarX]

It's electrical because of the lights dimming. (unplugged MAF, lines, fuel wont cause the interior lights to dim if you are good on the battery.) You could have gotten a bad battery or alternator. Is the alternator connected properly? Did you check all leads? Start the car up and and remove the battery while its on. What does it do?

Modern cars do not run without a battery connected...for the most part. Def not good for the ECU.

FWIW still sounds like your running outta fuel to me. Could be like Bruce said, the tune is for the wrong intake causing it to run lean, and then lean out and die. If you are throwing lean codes I wouldn't push driving it tooooo much.

 

[A John In NJ]

Modern cars do not run without a battery connected...for the most part. Def not good for the ECU.

FWIW still sounds like your running outta fuel to me. Could be like Bruce said, the tune is for the wrong intake causing it to run lean, and then lean out and die. If you are throwing lean codes I wouldn't push driving it tooooo much.

Me thinks its the tune as well. Im gonna order an Email tune today and take it from there.

I'll leave the car parked in the meantime.

I shall report back after that