BradlyB

So I have been having some issues with my 05 Mustang GT that both I, and the local Ford dealership, can't seem to figure out. The dealership has 'solved' the problem twice already, so I'm hoping to get some input before a third charge from them. I'll try to give a complete rundown of the situation from when it began, about 2 weeks ago.

Before I begin I should note that I do have some aftermarket parts. A 62mm MotoBlue TB, K&N CAI, Underdrive Pulley. Also aftermarket side exhaust from Cervini. And the car was tuned, when this all began, with a Diablosport performance tune.


It started, partly, when my battery died. It was the CD changer, or at least I believe it was (Ford says their CD changer doesn't drain the battery). I got in the car one morning and could hear the CD changer trying to change a CD before I even started it. I can only imagine it was trying to do this all night, and of course the battery was dead. Got the battery jumped without an issue, but when I did so I noticed quite a lot of corrosion on the positive terminal for the battery (some sort of green buildup, assuming from the copper used in the connection). So I unhook the battery to clean the corrosion, then hook it back up.

This is where the real problem starts. When I hook up the battery and start the car, I get an error code for the Throttle in Forced Idle. I believe it was 2104. The car moves, barely, but there is no response from the throttle at all.


The car is towed to the Ford dealership, they tell me my aftermarket throttle body is bad. No biggie, I have the stock one, so they put that one on and say the problem is solved. When I go to pick up the car it has error codes for Lean Air Mixture, 0174 and 0171. Ford tells me this is because the car was tuned for the TB, and when I flash it back to stock it should fix it. I do that, and the throttle forced idle error comes back.

So car goes back to Ford, this time they tell me the TB motor is bad. They replace that and give me the car back. Not instantly, but within a mile of driving the engine light comes on, error codes 0174/0171. I bring the car back to Ford. They tell me, again, that the issue is because of the aftermarket parts.

This doesn't make sense to me, to begin with. So they tell me when the car is tuned for higher air flow, that replacing the 62mm TB with the stock caused the lean code. Now when the car is factory tuned, they say the CAI is causing the error. How can it be Lean in both situations?

Additionally, I have never had this code before. I've had the TB/CAI on for over 5 years in various tunes, including the stock one, and never gotten a Lean code. And of course this is the error it gave me the first time they gave it back to me, and upon reflashing the tune it gave me the throttle error again. So I tell Ford to hold onto the car until they can tell me exactly why there is a Lean code, which is where it is now.



So I'm looking for suggestions for what might be the real cause of the problem. I've been doing some looking on my own, while Ford has had the car, to see what the issue could be.

I don't think it's the TB being dirty causing the forced idle code because it's done it on 2 TBs now.

The TB motor has been replaced, so it shouldn't be that.

It might be that Ford didn't reconnect the CAI back properly when they swapped out the TBs, which might give the Lean codes, but why would it revert to the throttle idle code when I reflashed it if that was the problem?

It could be the MAF for the Lean codes as well, but again why would it go to the throttle forced idle when I reflashed it if that was the problem?

Any advice would be greatly appreciated.