Air/Fuel ratio is wrong

[jgibson3]

I own a 2002 Mustang GT and, along with other modifications, it is tuned with the predator. I recently upgraded my fuel injectors from the stock 19lb/hr injectors to ford racing 30lb/hr high flow injectors and now the fuel/air ratio is wrong. It's running rich- I can smell it, the check engine light soon is on (I disabled the oxygen sensors with the predator temporarily and the light went off and stayed off and when I turned the sensors back on the light came back on, so I believe this problem has to do with it running too rich as well), and it is having idle problems which I also believe to be the fault of the air/fuel ratio. I was wondering if purchasing the Mafia and installing it will allow me to fix this problem? I was reading the instructions online and if I understood them right the car needs to be running well in order to install/calibrate the Mafia properly. Is this correct? Can I install the Mafia on an engine that is running bad to begin with in order to fix it? One more question- if this will work and I do buy the Mafia I wanted to make sure it will work properly with a K&N cold air intake kit. I dont think it would be a problem, but I want to ask just to make sure since I'm not too familiar with the Mafia and how it installs.

If you need anymore info like you asked for in that master thread (predator model and software revision to be specific) just post back or email me telling me where to find that info. I looked briefly but I didnt think it really mattered for this question so I gave up quickly.

Thanks,
Jonathan

[14.63lightning]

The first question would be what else if anything have you done to modify you vehicle. Because your car might not have needed the extra fuel you are delivering with the larger injectors. I think you will need to have a custom tune to get your A/F ratio correct to match the higher flowing injectors. Your engine is getting more fuel now with the same amout of air it was recieving prior to the injector swap. You will need to take some fuel out with your predator but I would reccomend having it tuned by a professional at a dyno. Also the MAFia is designed to compensate for the mass air sensor when it gets pegged past 5 volts or 4.80 volts. The more air you pull in the air intake the higher the voltage on the mass air sensor. This voltage signal is sent to the computer so it can compensate by adding the correct amout of fuel for the signal it recieved. When you build your engine to the point that it pulls enough air through it to peg the mass air sensor it can no longer add the fuel needed when you exceed 4.80-5 volts on the sensor. That is when you would need the MAFia. You would most likely be running lean when you need the MAFia. So no you do not need the MAFia. I hope I have answered some of your questiones. Good Luck Jonathan!

[jgibson3]

Thanks for the quick response and all the great info! Im impressed- I didnt expect anything until tomorrow at the earliest. Here is a list of all the mods I have on my car. I read that the 19lb injectors are only good to feed up to 300 hp and although ive never put my car on a dyno because it is so expensive I'm pretty sure im over 300 or at least pretty close.

Predator tune
Ford racing 3.73 Differential gears
Dual Flowmaster 40 series
K&N cold air intake
MAC underdrive pulleys
Maxspeed performance springs
Ford Racing High Flow 30lb/hr injectors
MSD Ignition coil packs

I also just replaced all the sparkplugs with champion iridium plugs so I know thats not the source of any problems

How much will it cost me to have a tune written? It sounds expensive- especially if Im going to have to retune it after most modifications. I dont even have the PC interface for the predator in order to send my current tune to you.

Thanks again
Jonathan

[LightningMike03]

The way I understand the MAFia is that on all but one of the settings it is basically leaning out the A/F ratio. Extending the 0-5volt range allows more air for the same amount of fuel.

Your real problem is that you have no idea of what you’re A/F ratio is doing. I agree that it is rich but without some idea of how rich, you are really shooting in the dark. The MAfia would probably help but you have no method to gage the adjustments. A Butt dyno is only going to get you in trouble.

You haven’t told us why you need the larger injectors but obviously they are larger than needed at this point. You should go back to maybe a 24LB injector and tune for that. Then as the need for more fuel comes along move up to the 30LB.

OK I see your list of mods: Don't get the wrong idea but what you've done will not change the HP more then maybe 25 at the wheels. The Predator tune is going to have the greatest effect of all the things youv'e done and it will compensate for itself. So I still don't see the need for larger injectors for a while.

[mikel]

I would suggest reinstalling the stock injectors.
Your MAF is calibrated for use with the stock injectors, and going to the larger injectors will cause fueling issues.

Thanks

[jgibson3]

Alright thanks for the info. It sounds like I'll just take those high flow injectors back out and save them for later. I dont remember where I got my horsepower figure from but I guess I was a little off.

Thanks again!

[Griffon327]

Is there a specific reason why people are telling him to remove a new set of injectors he just spent good money installing? Agreed looking over the list of mods he does not need to run 30 lb injectors at this point but since injectors are not cheap and the only reason they are not running properly is that the MAF has not been calibrated for the 30 lb injectors then why not simply calibrate the MAF and be done with it? otherwise the money spent on the injectors will be a waste.
Also cannot a custom tune of the PCM calibrate for the size of the injectors so that the need to calibrate the MAF is no longer needed? I am thinking SCT and others can do this so why can't the predator do this? and if it can then why is someone telling him to remove the injectors when there is a possibility a set of ported heads and camshafts might be installed shortly thereafter?