Progress Thread 2003 Mach stalls

Mach1Alfred said:

Hello all

I have a 2003 Mach 1 that stalls when AC is turned on when the car reaches its normal temperature. IAC, MAF & TB have been cleaned also checked for leaks and all clear. I have also changed the O2 sensors upstream. The Mach also stalls at times in stop/red lights AC off.

After the built the Mach would stall here and there while slowing down or complete stops obviously needing a tune. RPM’s at idle would be around 8-9 roughly, now just before the tune my brother swap the battery and connected it backwards for a good 2 seconds. Lighter and stereo fuse are the only fuses that blew but the Mach didn’t feel the same. At idle it would now be at 5-6, it would struggle more to stay on. I got the tune done but the stalling is still there I feel it stalls even more after the battery incident.


Modifications
Engine built .30 over
Camm work
MAF 90
42lbs injectors
CAI JLT
Off X pipe
Chipped and tuned

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Mach1Alfred said:

Hello all

I have a 2003 Mach 1 that stalls when AC is turned on when the car reaches its normal temperature. IAC, MAF & TB have been cleaned also checked for leaks and all clear. I have also changed the O2 sensors upstream. The Mach also stalls at times in stop/red lights AC off.

After the built the Mach would stall here and there while slowing down or complete stops obviously needing a tune. RPM’s at idle would be around 8-9 roughly, now just before the tune my brother swap the battery and connected it backwards for a good 2 seconds. Lighter and stereo fuse are the only fuses that blew but the Mach didn’t feel the same. At idle it would now be at 5-6, it would struggle more to stay on. I got the tune done but the stalling is still there I feel it stalls even more after the battery incident.


Modifications
Engine built .30 over
Camm work
MAF 90
42lbs injectors
CAI JLT
Off X pipe
Chipped and tuned

Click to expand...

wmburns said:

Seems to me that there's a real chance that the P0141 is not helping. With this outstanding DTC there's no way that the PCM is in closed loop mode.

Anytime the PCM calls out a circuit malfunction that means there's something sooooooooooo wrong with the circuit that the PCM is unable to perform any real trouble shooting.

If this were my car, I would first check fuse F2.2 and F2.8 to see if they are blown. Next I would check the wires to/from each of the O2 sensors to look for wiring harness damage. For example physical damage such as touching hot exhaust.

1999-2004 MY fuse panel schedule:

1999 Mustang GT with 2001 motor swap, wont fire. Please help

First off thank you for taking the time to read this, I hope that you will be able to help me out in some way to get a 4 month project off the ground and back onto the streets. I'm not a master mechanic but know just a little bit, enough to do your typical maintenance, overhauls, and swaps. I...

www.allfordmustangs.com

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wmburns said:

Am I good or what?

Given the fact that fuse F2.2 powers to IAC is it a surprise there's a problem with the idle? Plus none of the other 12 volts sensors are working either.

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wmburns said:

Soooooooooooooooooooo. Did you check to see IF the fuse blew again?

Do you KNOW WHY the fuse blew in the first place? I don't know about your car but I have owned cars for years without ever replacing a fuse.

Again, if the IAC is not working because of a blown fuse is it a surprise that the idle is unstable? I'm including some information about how to trouble shoot IAC issues. Since your car does continue to run with a blown F2.2 fuse (non functioning IAC), the only reasonable explanation is some has attempted to adjust the throttle body idle stop screw in an attempt to keep it running. The result will always be that the car will idle in the exact conditions that the stop was set but won't when the temperature changes are the motor load changes. Note the part about what should happen when the IAC is disconnected (motor should die outright or run very slowly).

Troubleshoot IAC idle problems 1996-2004

Troubleshoot IAC idle problems 1996-2004

Back to the basics. Check for blown fuses. Especially fuse F2.2 and F2.8 in the Central Junction Box (CJB 1999-2004 MY). Confirm key on power using a known good ground. 1999-2004 MY fuse panel schedule...

www.stangnet.com

Just wondering. Did you read the information in the "how to perform a voltage drop test"? How about the part where it says, "today's cars simply will not run right without a strong battery and charging system"? When a problem occurs when there's a large electrical step load change this screams there's a problem with the charging system. The system voltage is not stable for some reason. Do yourself a favor and find out WHY before doing anything else.

I personally would be very upset if someone attempted to tune a car that wasn't working well in the first place.

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Mach1Alfred said:

Awesome knowledge, thank you I wouldn’t of known about the fuse since the tester was indicating good. My car sat for a bit and my brother crossed the battery cables for a good 2 seconds, it blew the regular fuses radio cigar lighter and the F2.2 that I didn’t know about with this said yes I messed with the screw a bit but before I did I marked it. I will put it back in place.
FYI when I would disconnect the IAC it would die ASAP but that test was done with the fuse blown. I will try it again.

Yes it’s upsetting I seen other tuner’s on you tube they won’t do ANYTHING until the car is running correctly. Lack of knowledge my end.

I will read it again on the voltage drop test, mind you before the cables were crossed the Mach wouldn’t do what it does now.

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