Why am I running lean???

[instangator]

On a hot day with the stock tune and 93 octane my car has some pinging. I received my mail order SCT Tuner today and after installing the tune the detonation obviously got worse. JMS Chip seems to think something is wrong with my car to make it run lean.

I checked the MAF voltage and it is at .79 volts at idle. I checked for vacuum leaks using brake cleaner but couldn't find any. I tightened all clamps and hoses and cleaned the MAF, but the detonation is still there. The CEL isn't on and no codes are thrown. Why would my car be running so lean?

 

[Go HoTO!]

Man, that's a tough one. Sounds like you are doing all the right things. Please keep us posted.

 

[CTGrey02]

Too much timing? Back it down a degree or two until your figure it out. How are your spark plugs? Check em.. especially if you havent already. Try switching to a different brand of fuel as well. Try cleaning your fuel system. Check your air filter. Oil change if you havent already.. basically due a tune up. Rule out the little stuff before moving onto the big stuff.

 

[KaPPaBaLL]

where did you get your SCT tune from? do you have a C&L maf?

 

[instangator]

This is with stock timing. I haven't checked the plugs but they only have 15000 mi. on them. Air filter is good as well as the oil.

The tune is from JMS Chip and I don't have a C&L MAF.

 

[KaPPaBaLL]

could it be the oil on the K&N filter being too excessive?

 

[instangator]

I thought that might have been it as well. So, I cleaned the maf, but it didn't help.

I changed the fuel filter and used a 3 step fuel system cleaner and the detonation isn't as bad. But, it is overcast and not nearlyas hot today, so that may be why its not as bad.

 

[instangator]

UPDATE!
After fighting with the detonation all day, I decided to put everything that involves air or fuel back to stock. So I put on the stock plenum & throttle body and stock inlet tube with paper filter and snorkel. Finally, the detonation is gone even with the aggressive tune and 93 octane!

Now the only problem is the car feels much slower without all the intake stuff. I was really surprised by the difference I felt. So now I am going to start putting everything back on one at a time to try and find the problem causer. At least now I have it narrowed down to the K&N filter and Pro-M conical filter adapter, C&L Inlet Tube, or the C&L Plenum and Accufab 75mm TB. All I know is it is going to be a long night,