03 Mustang gt 1131 & 1151-Fuel Air metering

[ndean52]

I have a 2003 gt, MAC Catback- Long Tube Headers- offroad H, accufab 75mm throttle body & plenum w/ steeda spacer, JLT Raim Air Intake, steeda underdrive pulleys, hypertech thermostat, .410 gears, and an sct flip chip w/ dial & 4 tunes.

I posted a thread a while back about my car sputtering, tried a fuel pump (the mechanics diagnosis) and didnt fix the issue. So i decided to get some spark plugs, which has helped. It didnt sputter for a while and now it does in rarely. I ran the codes and the same popped up as before, 1131 1152 - fuel air metering. Another mechanic has told me to replace the MAF.

Here my question/questions. I have read about the 90mm MAF that was used on the ford lightnings and really want to try this out along with some bigger injectors, both are stock currently on my stang. Would the 90mm be too much for my car and if not what size injectors should i get? Also, I heard you do not have to tune the 90mm MAF that was used on the lightnings? Is this correct, becuase i thought you had to tune them.

Any suggestions would be great about adding some HP!! Thanks guys.

[Blue)(Fusion]

Whenever you change the MAF or fuel injector size, you must get a tune otherwise the ECU is receiving false data from MAF and commanding injectors based on wrong fuel flow.

And from what I've read this does not mean the MAF is bad. It means that the ECU is unable to get the left and right banks within normal fuel/air ratio with the fuel trim.

This can be caused by a vacuum leak, bad HO2 sensors or a bad MAF sensor.

I'd start by looking for a vacuum leak. Listen for any hissing, inspect all the hoses as best you can visually and use propane or carb cleaner sprayed around the vacuum hoses to see if the engine changes RPM. If it does, there's a vacuum leak in that area and must be fixed.

If you have over 100k miles, change your HO2s anyway. They usually last 80-100k before they start getting lazy.

If you know anyone with the hardware and software to data log the ECU PIDs, you can monitor data from the HO2s, MAF, fuel trims, etc. and try to narrow it down. I bought pro software and a decent OBD-II device for around $200 and is well worth the money for situations like this in my opinion.

If interested, here is the device I have and I use the ScanXL Pro software witht he Ford enhancement add-on, although the free software that comes with it should work just fine: http://www.scantool.net/scan-tools/p...d/obdlink.html

[ndean52]

thanks bro, i dont have any O2 sensors on my car, so i bet thats the problem, i really appreciate your help. Nothing sucks more that not enjoying your car because of some bullcrap wrong with it and nobody can figure it out. Thanks again

[Blue)(Fusion]

Yeah you can do without the rear O2 sensors. They just tell the ECU whether the cats are working properly or not. It may not be legal in your state/county however to remove or disable these.

The HO2 sensors infront of the cats are very necessary as they control the fuel/air mixture. I'd go with OEM Motorcraft HO2 sensors since they seem to work the best with the 4.6 engines, especially with such an important sensor. Stay away especially from Bosch.