Texas Twin T

as of today I have replaced the spark plugs with NGKs, ran seafoam in the gas(8 gallons of gas),cleaned MAF sensor, replaced S2B2 O2 sensor and still have the problem and I am not getting any CELs. My gas mileage is about 27mpg and runs smooth down the highway. I STF and found something about temp sensor or EGT sensors that may cause problems and not give any CELs. HELP!!!

MarkFank

A bad EGT will not always throw a CEL. You need to check fault codes with a VAG tool.

S4_4MY30'S

First thing you should've replaced is the "UPDATED GREEN COOLANT TEMP SENSOR".

ErikS4

I had the same sumptoms - problem was my temp sensor. The low-temp sensor.

pitchS4

2nd. have you run vag yet?

Texas Twin T

Yes, no fail codes

pitchS4

Sometimes a loose TBB can cause rough idle too.

Texas Twin T

The sensor at the end of the lower radiator hose?

Texas Twin T

I let it set for 5 mins after upgrading my ECU. Had the same problem before changing to the APR chip.

pitchS4

The RPMs didn't jump around much and I wasn't throwing any codes so I didn't worry about it. Since I did the Timing Belt/Water Pump in December it has been smooth as butter. Note that I did my spark plugs in Dec too, so the T-Belt wasn't the sole factor to eliminating my rough idle.