Car stalling out. Help?

[Gray_Ghost]

Baseline: '03 Mustang GT auto. 110k miles. Engine mods: UPR Fenderwell intake, PP 75 mm throttle body & intake plenum, NGK TR55 plugs, and a SCT Tuner setup for the 87 octane canned tune. Both yesterday & today the car died when coming to a stop after approximately 40-45 minutes of driving. Average temp out side mid 80s. AC on. No check engine light, gauges reading normal until it dies. 3/4-1/2 tank of gas. I'm wondering if it might be bad gas, but the car is running fine while driving. Also, it looks like on the last down shift when slowing down that the RPMs are dropping too low and it just stalls. Any thoughts or suggestions? I'm going to put the stock tune back in before I leave out tomorrow to see if that might be the cause.

 

[jymboslice]

Check the IAC valve or check your vacuum lines

 

[Riddla]

Also check your cops.
Mine did the same thing and i replaced the iac and still did it. Ended up being a bad cops. Drove fine but when you were coasting to come to a stop and pushed in the clutch the car would stall. Fired right back on.

 

[Gray_Ghost]

Thanks guys. I'll start with the IAC, then try the COPs.

 

[Gray_Ghost]

Update: I changed the IAC and it didn't help. So I bought all new COPs. That seemed to fix the issue. Until today coming home. I got on it on the freeway on ramp and when I went to exit off the idle wouldn't go below 1200 rpms. Pulled over, cut the car off. It started fine back at a "normal" idle. Then I got on it again and it did the same thing with high idle for a second before dropping back to normal. What. The. ****!

 

[Adiabatik]

When was the last time the fuel filter was changed?

 

[HRTBRKR]

Check vacuum lines exiting pcv @ valve cover to plenum. The lines are known to collapse together and cause this problem.

 

[BawseOG]

when I installed an o/r x pipe on my gt, i didn't put the cone insert on the passanger side, it acts like a gasket between header and x pipe, my car would stall out on me when coming to a stop, i think the o2 sensor were reading extra air coming in thru the gasketless pipe and that caused the stalling.... installed cone/gasket and it hasn't stalled since.

 

[Stryker27]

fuel filter ...just my guess.