Took my car to a dyno tune shop, because it knocks sometimes when I get into it. They ran a diagnostics and my A/F was a 16, then went up to 17 and 18 in the midrange RPM then back down to a 16 in the upper RPM's. They told me to take it easy on it until I get it straightened out. They tried making adjustments with my SCT X2 programmer, but it won't let you actually get into the tune. Pisses me off, because with my Diablosport Predator it would let you do all that. I'm going to have to fax my results to JDM so they can give me another tune. I don't know what else to do.

 

Yikes!

While you are waiting - look for air-leaks in the intake... Just had that happen to my wife's car when the bozi at the repair shop mis-seated the intake tube on the throttle body...

This was not a mustang, but the same theory of "un-metered" air applies...

Look for anything in the intake path after the MAF sensor that could be letting in air:

lose/mis-seated intake
PCV not all the way on
broken PCV hose
cracked intake hose

It may be that the tune, your O2 sensors or MAF are malfunctioning as well - JDM can help you with that...

 

Yeah it does seem funny that it never did it before, then one day it started with the knocking.

 

Those #'s are high enough that unless someone snuck up and re-flashed your tune in the middle of the night something is either lose or a sensor has failed...

 

+1 to cekim. you should be in the mid 12s for your a/f ratio. 16 is way high! definitely examine the intake path after the maf. look for leaks because thats what it sounds like you have.

 

I will look. Thanx guys. This is frustrating, because if I don't find anything do I take it to my dealer?

 

In theory an reputable repair shop should be able to deal with this, there are a limited number of things that can cause it and basic A/F debug is pretty straight forward regardless of the car:
Check MAF readings/voltage/wires, check for vacuum leaks, check intake path for leaks, check O2 readings, check computer...

Ideally, you would take it to a shop that has dealt with the Saleen's before so that they know what to expect when it comes to the re-wired MAF and so on...

So, if you had a "good" dealer and/or one in the area that does Saleen installs then yes.

If not, I'd call around and see if I could find a shop that deals with supercharger installs before going to the dealer. Many service departments have degraded to thepoint that if the computer does not tell them the car is on fire, they will hand you the keys and send you on your way in your flaming car witha smile (and a diag bill).

 

I'm surprised I don't throw a code or an idiot light telling me I'm running to lean.

 

Well, non FI engines can take 16-17 without exploding...

That doesn't completely excuse it, but A/F jumps around a lot at various points during the accel/decel process, so I suspect they just made the range wide enough that it did not catch momentary fluctations...

It might eventually throw a light when the "long term" trim tables get screwed up...

This would be why many FI people suggest aftermarket A/F guages - the idiot light often won't come on until the clunk in the engine has already told you what happened...

 

By the way, sometimes it knocks at WOT and sometimes it don't. If that helps with a diagnosis. I'm going to put on a new MAF sensor I have and see if that helps.