1st off I have a canned 91 race tune from Diablo. But lately my car has been sputtering sometimes from a low rpm. It feels like it loses power for a second then kicks back in. It only does it sometimes it doesn't make any crazy sounds but it hesitates for a second but only at a low rpm range. I've had this tune for a few months now so I don't know if its the tune or what. It just started doing this last week. BTW my car feels slower also since this started.

 

also i've been running 93 octane in my car since I had the tuner but it has a 91 canned octane tune on it. Don't know if this could be the reason? Just don't know what it could be please help.

 

sounds like a coil breaking down to me

 

Always start with the basics: clean the TB, clean the MAF, replace the fuel filter, clean the air filter, fill the tank with fuel from a different station, run some Techron or SeaFoam. Then begin looking at hardware or sensor issues.

 

^ yes, also the vacuum hose, try checking that out

 

thanks so much guys. have any of you ever experience something like this before?

 

Mine was hesitating and cutting out thought it was the tune.. ended up being the fuel filter went with a high flow steeda unit hasnt done it since.

 

I had some coils drop in a 5.4L and it sounds like what you are talking about. No engine light either

 

Maybe this will help:
http://iihs.net/fsm/?dir=9&viewfile=Step 2- No Diagnostic Trouble Codes (DTCs) Present Symptom Chart Index.pdf

(not sure why the hyperlink is messed up)