S4 Running Bad Until Warm

[cpo3619]

My 2001 Stage 3 S4 has been running bad after it sits overnight, only for about 1 minute or so until it warms up a bit. After I drive it for a few minutes, it idles and runs good all day on startup. I have tried new plugs and coolant temperature sensor. Today I unplugged the MAF and it started great and even seemed more responsive. I have the 034 Motorsport 85mm Billet MAF Housing with a bosch maf element. Could the MAF just be bad? The only codes im getting are bank 1 and 2 running rich. But I have a wideband and its nothing too abnormal. AFR's are still close to where they should be. Thanks for the help

[Peter1.8t]

Unplug MAF and see if that helps.

[cpo3619]

Unplug MAF and see if that helps.

If you read my post it says I unplugged the MAF and it runs good

[getslideways]

Just out of curiousity, what are your long term multiplicative and additive fuel trims showing?

http://wiki.ross-tech.com/wiki/index.php/Fuel_Trim_Info

"Add" means additive trim, which is addressing an imbalance at idle. When the ECU is using additive trim, it is telling the injectors to stay open a fixed amount longer or shorter. The malfunction (e.g. vacuum leak) becomes less significant as RPM increase. For additive adaptation values, the injection timing is changed by a fixed amount. This value is not dependent on the basic injection timing.

"Mult" mean multiplicative trim, which is addressing an imbalance at all engine speeds. The malfunction (e.g. clogged injector) becomes more severe at increased RPM. For multiplicative adaptation values, there is a percentage change in injection timing. This change is dependent on the basic injection timing.

You can check your current state of trim by using VAG-COM or equivalent to look in Group 032 (in many modern ECU's, consult your Factory Repair Manual for the specific group for your particular vehicle) in your engine measuring blocks. The first two fields will have percentages. The first field tells the fuel trim at idle (Additive). The second field tells the fuel trim at elevated engine speeds (Multiplicative). Negative values indicate that the engine is running too rich and oxygen sensor control is therefore making it more lean by reducing the amount of time that the injectors are open. Positive values indicate that the engine is running too lean and oxygen sensor control is therefore making it richer by increasing the amount of time that the injectors are open.

It is totally normal for both the first and second fields to be something other than zero. In fact, zeros IN BOTH FIELDS indicates that either you just cleared codes (which will reset fuel trim values) or something isn't working properly. If values get too far away from zero, it will cause a DTC (fault code) and can set off the MIL (commonly referred to as the Check Engine Light, or CEL). Specifications for normal operation are usually somewhere near +/- 10%.

In general, an out-of-spec value in the first field (Additive) indicates a vacuum leak since it is mostly present at idle, when vacuum is highest. An out-of-spec value in the second field (Multiplicative) indicates a fault at higher RPM, and may point to a faulty MAF.

[cpo3619]

Thanks, I will have to try that. I had to order a new VAG scanner because mine took a shit. I am guessing its either the MAF or a vaccum leak because of the fact that it runs great with the MAF unplugged. I boost leak tested the car and didn't hear anything so I'm leaning towards the MAF. I don't believe it would be a dirty injector. Again the only codes I am getting once this problem arrived are bank 1 and 2 rich.