Need Help: CEL on when a iphone is connected during idle relearning?

[Figo]

The CEL on tonight.
I am worrying whether anyone had similar experience before.

Here is my setup
Scion FR-S 2013
- Vortech Supercharger ECUtek Dyno Tune
- JDL UEL Catless Header
- JDL 2.5 inch over pipe
- JDL 2.5 inch ultra-quiet front pipe (catted)
- ARK Grip Catback

To make long story short

I have a exhaust leak 3 weeks ago. The leak was bad. First time the front pipe was crack. After the crack was welded. I got a gasket leak issue(gasket between header and overpipe, overpipe and front pipe, front pipe and catback). And last week I fixed it. Now the exhaust is ok without any leak.

But the idle was not stable after I fixed the leak. The rpm dropped to 500 sometimes and the car shake, especially when I step on the clutch all the way down. it happended about every 5-10 mins. I think it might be because the exhaust is not leak now and I need to do a idle relearn.
I got unstable idle issue before and have done this idle relearn at that time.

I did a idle relearn tonight(disconnect the battery). I turned off AC and all electrical device on my car, waited for about 5 mins and the idle was stable. After 6 mins, the girlfriend got on my car and connect a iphone to the USB port to charge and to play music.
Then after about 2 mins, the idle dropped to 500 rpm twice and the car shake as it will die. Then the CEL was on.
I restart the car again, and the CEL was still on.
Then I disconnect the battery, and did the idle relearn again. The CEL was off. I wait for 10 mins and the idle was still stable. I turned off the car, then turn it on again, drive about 15 mins, everything is good.

Now the CEL is off, and everything seems ok. But as I said I only tested it for 15 mins.


My questions

1. Will a charging iphone draw the current from the car and lead to idle unstable and even CEL?

2. Can people read the CEL code now even if the light is already off?

3. I am not sure the last time I tuned the car (half a year ago) the exhaust was leak or not. Is that a possible cause? My guess is that the exhaust was leak at the time that the car was tuned, now the leak was fixed, and the tune is not suitable for this setup any more because it was for a “leak exhaust setup."

4. Is it a boost leak? I have a OBD reader. The boost was about -20 at stable idle and change when rpm was not stable.

5. Is it a misfire?


Anyone has any suggestions?

Thank you!
.

[steve99]

Could be a zillion things

I doubt plugging in the phone did anything , just co-incidence.


You should be able to read stored CEL codes even though the code is not active.

Look at you Long Term Fuel trims at idle and low rpm LTFT , if they are high like 10% plus then you likely have a leak in intake/exhaust or damaged 02 sensor ect.

Sometimes if your battery is on the way out you can get weird intermit problems and cel codes.

[Figo]

Originally Posted by steve99

Could be a zillion things

I doubt plugging in the phone did anything , just co-incidence.


You should be able to read stored CEL codes even though the code is not active.

Look at you Long Term Fuel trims at idle and low rpm LTFT , if they are high like 10% plus then you likely have a leak in intake/exhaust or damaged 02 sensor ect.

Sometimes if your battery is on the way out you can get weird intermit problems and cel codes.

Thank you.

The battery is good, I just change the stock one to optima yellow top two months ago.

I will bring the car to a tuner tomr to check the stored CEL code.

For the exhaust, I did not have the CEL issue even when the front pipe was crack. lol.