OK so i am getting hesitation with no cel. I have vafc and aem cai. I pulled to plugs to see thier condition. They seemed clean. The tips where the spark happens was white. I cleaned them and gapped them. the middle part of the plugs where its all white had some brown burnt coloration. Do they need to be replaced? I tried tapping the map sensor with no avail. I have recently reset my ecu, could that be the cause? any suggestions?

George

 

With a VAFC, it could be anything. Is it tuned right? And can you be sure? Bad connection on one or more wires? White on the spark plug tips would indicate running a bit lean.

 

yeah i got the vafc tuned and i have a harness, so i dont think its the wiring...i guess i will take off the vafc and see if thats it...thanks for the suggestions...anymore/anyone else?

 

Doesn't white usually mean that the car is running lean?

 

Resetting your ECU will set your LTFT (long term fuel trim) and STFT (short term fuel trim) back to OEM settings. It will take your car a week or so to re-learn what it needs to function normally.

Utah

 

If your V-AFC was tuned for narrow AND wide throttle fuel corrections OR your throttle position settings are low, you will get hesitation and sputtering. You should consider setting all narrow throttle settings to 0, and raise your Lo / Hi throttle position settings much higher. I set my throttle settings at 80% / 81%, so the fuel corrections only effect WOT. This will also prevent the ECU from tuning out the V-AFC over time.

 

BTW, resetting the ECU every now and then is great for refreshing the power band, but will idle like crap for a few days after.

If you have the OEM plugs, I suggest going 1 step colder. I have been using IK24s for a year, and they run much more consistent.

 

My impression is that resetting the ECU screws up my low speed throttle response as well as my idle.. maybe just my car but any slight improvement in WOT is not worth the price to me. I don't do it anymore and reset any code with the OBD SW.

 

gernby,
The hesitation only happened at certain throttle (around 40% and at only 3-4krpms) and actually my car was tuned for low throttle so I zero'ed the settings for low and changed the l/h throttle settings from 40/50 to 70/71. So far so good (i also changed the plugs). Thanks for the advice...hope this works

 

If it still does it, you should reset the ECU, since your narrow throttle fuel corrections may have tainted your STFT and / or LTFT.