Sputters At Low RPMs When Car is Cold, Dies While Driving.

brentwoodboy said:

Hi, I've been driving a 99' GT with 120K on it for about a week, and when it is cold it sputters under load. In first, I have to let the clutch out at high RPMs so it doesn't sputter. When I am coasting with the clutch in, the RPMs slowly fall down under 500 then die. I am a 5.0 kinda guy so I have no clue what this could be. Plugs? IAC? Fuel filter? Dirty MAF?

Click to expand...

Have the plugs been changed and if so when? Clean the MAF since that is very cheap to do and when was the fuel filter changed? If you don't know, then replace it anyways to be safe. Seems to me like plugs or fuel filter because i dont think a bad IAC causes sputtering, it mainly causes the rpm's to flucuate alot. BUt a new one is 45 bucks, so at 120k you might as well get one

Could also maybe be a crankshaft position sensor (although I'd think this would throw a code) ... Just be careful cleaning the MAF.

ever get this problem worked out? I got a problem just like it

sounds like bad load of gas , change the filter first if you have a tester hook with the bleeder hose hook it to the shrader valve then with the key on not running bleed off some gas into a clean jar , if it comes up muddy you have your problem , theres lots of gas stations with filthy gas tanks under the ground , one bad load & you get problems like you described , I bought a gas tester about a year ago its a great tool paid $45 make sure it has the bleed feature .....

My money is on the plugs or IAC.

But you need to check tons of things: plugs, IAC, COP boots, MAF, TPS, PCV/grommet, fuel filter, injectors..the possibilites are endless

It would be great if you could data log your car and check the voltage going to the MAF and IAC....

TSB
01-1-9 DRIVEABILITY - HESITATION WHEN COLD - WITH NO DIAGNOSTIC TROUBLE CODES (DTC) PRESENT - VEHICLES EQUIPPED WITH 4.6L ENGINE AND MANUAL TRANSMISSION

Publication Date: JANUARY 11, 2001

FORD: 1999-2000 MUSTANG


ISSUE:
Some vehicles may exhibit a hesitation and in some cases engine backfiring through the induction system on cold starts (27°C/80°F and colder) with no diagnostic trouble codes (DTC) present. The hesitation is exhibited on a low speed, high load condition. This may be caused by the calibration of the Powertrain Control Module (PCM).

ACTION:
If condition is verified and normal diagnosis cannot pinpoint condition, reprogram the PCM to the latest level calibration. Refer to the following PCM Calibration Information Chart. Refer to the appropriate year Mustang Workshop Manual for reprogramming procedures.


PCM CALIBRATION INFORMATION
Application Old Part Number (-12A650-) Tear Tag New Part Number (-12A650-) Old Calibration New Calibration NGS/WDS Qualifier
1999 - 4.6L 2V T-45, Fed., 16 inch tires XR3F-ZD FTL3 XU7Z-AAA 9VXM-AAC 9VXM-AAC N/A use WDS
1999 - 4.6L 2V T-45, Fed., 17 inch tires XR3F-AAD GTG3 XU7Z-ABA 9VXM-ABC 9VXM-ABC N/A use WDS
1999 - 4.6L 2V T-45, Calif., 16 inch tires XR3F-ABE HJX4 XU7Z-ACA 9VMM-BAD 9VMM-BAD N/A use WDS
1999 - 4.6L 2V T-45, Calif., 17 inch tires XR3F-ACE JKU4 XU7Z-ADA 9VXM-BBD 9VXM-BBD N/A use WDS
2000 - 4.6L 2V T-45, Calif., 16 inch tires YR3F-DA KPL0 YU7Z-CMA 0ZE2GB0B00 0ZE2GB0B00 N/A use WDS
2000 - 4.6L 2V T-45, Calif., 17 inch tires YR3F-EA JRX0 YU7Z-CNA 0ZE2GAB0B0 0ZE2GA0B00 N/A use WDS