A/F ratio

[96stangn]

I got the PI headswap done on my 96' GT. The check engine light came on and the error code was that the air-to-fuel ratio was too lean. After driving it for a day, the check engine light went off and everything seemed to be fine. However, the check engine light is back on with the same code, but there is definite detonation when the car is under load and the rpm is the 1200-2000 range. I was wondering if resetting the EEC-IV would fix the problem. I am a little new to this, so I am not even sure how to go about resetting it. Would I have to go into the EEC-IV harness and detatch it and put it back or is there an easier way?
I was also planning on bringing my car in to get dyno tuned chip installed to correct the a/f ratio once and for all. Should I think about getting bigger injectors? Any ideas would be great.

 

[JoeySperz]

If you are running too lean you should look into a new fuel pump and injectors. I would strongly suggest getting a proper tune, because if you run too lean you can throw a rod through your oil pan. I would suggest getting this taken care of asap unless you want to chance having to rebuild your block.

 

[96stangn]

What size injectors and fuel pump should I get to correct the problem? Would that fix the problem? I really want to get my car tuned, but the shop where I can get it done will not be able to do it for another 2-3 weeks.

 

[JoeySperz]

When i put in my supercharger, i am going to do 42# injectors. I'm not too sure about the pum i am going to do yet, but i have heard a lot of good things about the 2003 Cobra pump. That should be enough for your engine, but i just wouldnt beat on it until you got a proper tune.

 

[ph4926]

I don't think it could be your injectors I also dont think it could be your fuel pump you would get a different code.
It would make more sense that you have a sensor problem eather causing your ecu to lean it out or just getting a bad signal. I would take it to a dyno and just pay for one pull to see if the A/F is realy off. By far some of the best info I have ever got came from my tuner.

 

[Noble Steed]

When was the last time you replaced the fuel filter?

 

[Blk03GT]

What kind of air filter are you running?

My Expedition came with a stupid K&N charger system and I got that very same code. I only bring it up cause it also has the 4.6.

 

[Blown99]

Your injectors and fuel pump are fine for your application. You probably have an O2 sensor that is out of range. When was the last time you changed them? Check your fuel pressure and flow. Check for vaccumme leaks!!