Engine 2003 Gt Problem And Obdii Code Question

[93-331-29psi]

So my oldest son has become a second generation Mustang enthusiast, but recently he has been having issues with it and is about to give up. I have searched but couldn't find an exact answer to the question. Car is a 2003 auto with CAI and otherwise stock. This car is worse than a woman. It has good days and bad days since we bought it about a year ago. Recently we've discovered the P0340 code and I plan to replace the alternator as the forums have all suggested.

Transmission codes are popping up (don't recall which one), car idle is erratic, had numerous coils fail (replaced all), have an evaporated canister code. If we're getting a P0340 on bank 1 code and also getting other "Bank 1" codes such as o2 sensors. Could the cause of the first be the cause of the others? In my mind I would think that they could all be related but I don't know from experience. I suspect there is a bad alternator which is causing all sorts of "electrical" type issues throughout the system.

Also having an issue pumping gas into this think. It'll take $.25 and kick off. Irritating and it takes about 30 minutes to fill the tank.

 

[wmburns]

I can help you with the slow gas filling problem. It's caused by a clogged charcoal canister. To prove it's the problem try blowing through the charcoal canister. If you can't, diagnosis confirmed. I have direct experience with this same issue and can say from first hand experience about the fix.

But before replacing the charcoal canister double check that the CV vent solenoid isn't clogged. Sometime dirt or insects will make their home in it. Further having an EVAP DTC code could also be caused by a clogged canister. A chance to fix two problems with one repair.

Regarding the P0340 DTC you are very smart to check the alternator before replacing any sensors. Here's some more information regarding DIY alternator testing and trouble shooting.

Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-fo...perform-charging-system-voltage-drop-test.56/

Here's some information on how to trouble shoot idle/IAC issues. Again much of this assumes the car is in basic good working order. Take care of any "serious" DTC's first.

Troubleshoot IAC idle problems 1996-2004
https://www.stangnet.com/mustang-forums/resources/troubleshoot-iac-idle-problems-1996-2004.13/

 

[93-331-29psi]

Alternator was confirmed bad (failed bench test) and has been replaced. Engine codes were gone and the car ran great for about 5 miles then I randomly started getting cylinder misfires and power loss under acceleration. Coils and injectors are new so I don’t suspect them to be the cause. I say that only because misfires seems to be random. 1,5,6 one run and 2,7,3 next time etc. Nothing that points to one particular cylinder as the culprit.

I’m suspicious of two thing. First being the computer only because that seems to be a common denominator plus a snap-on scan tool doesn’t recognize it (odd ???). I also suspect there may be a bad ground somewhere but I have no idea where to start looking. I thought maybe the fuel pump wasn’t putting out enough pressure but the dropping of cylinders kinda rules that out.

Fuel issue isn’t he evap canister. I’ve pulled that (disconnected hoses) and same issue. I suspect its the valve/vent thing on the top of the tank.

Ideas?? Please help

 

[wmburns]

I also suspect there may be a bad ground somewhere but I have no idea where to start looking.

Finding a bad ground is the same concept given in the "How to perform charging system voltage drop test". Another method is to perform a resistance measurement using a Volt-Ohm Meter (VOM) back to battery negative. As a remember that an accurate reading requires an inactive circuit.

First being the computer only because that seems to be a common denominator plus a snap-on scan tool doesn’t recognize it (odd ???). I also suspect there may be a bad ground somewhere but I have no idea where to start looking.

Perhaps there's a common cause. The ODB2 connector itself has power at pin #16 (LG/RD)-Fuse F2-31. Grounds at pin #4(BK)-G204 and #5(BK/YE)-G104

Fuel issue isn’t he evap canister. I’ve pulled that (disconnected hoses) and same issue. I suspect its the valve/vent thing on the top of the tank.

Does that mean the Evap DTC code remained or the slow gas tank re-filling problem remained?

As a reminder that if anything in the EVAP system is disconnected it would be expected to still have codes. Further it does take drive cycles after a 8 hour cold soak before the PCM will run an EVAP purge.