Cold idle problem

[schienbeinj]

I have a 2002 996 3.6l Carrera and when cold, it idles, but giving it any gas makes it bog down and the revs drop, similar to a carbed engine with the wrong choke setting. Once the engine reaches normal operating temperature it runs fine. I'm guessing a temp sensor is faulty and the fuel mixture the engine is getting is incorrect for its temp. Has anyone else experianced this and how can I diagnose the problem, I have an OBD 2 reader but it isn't showing any codes. I have cleaned the throttle body and MAF and no improvement.

[logray]

Using your code reader, have you monitored the following from a cold start?

O2 sensor pre-cat voltage

Coolant temp

Air mass

LTFT (or FRA)

STFT (or RKAT or TRA)

[schienbeinj]

From cold, intake air temp 46F: Air flow 1.455 lb/min, LTFT B1 was -4.2, B2 was -14, STFT B1 was 0, O2 B1S1 was 0.8257v

at ECT 98F: Air flow was 0.760, LTFT B1 was -0.7 B2 was -9.3, STFT B1 varied 1.5 to 5, B2 varied 4.56 to 9.3

at ECT 108: Air flow was 0.735, LTFT B1 was 0, B2 was -7.8, STFT B1 varied 0.7 to 3.9, B2 varied 3.1 to 5.4, O2 varied 0.105 to 0.660

at ECT 123: Air flow was 0.694, LTFT B1 was 0.7, B2 was -6.2, STFT B1 varied 0 to 3.9, B2 varied 0.7 to 4.6, O2 varied 0.1 to 0.675

at ECT 140: Air flow was 0.661, LTFT B1 was 1.5, B2 was -6.2, STFT B1 varied -2.3 to 1.5 B2 varied -1.5 to -0.7 and O2 0.150 to0.7

At 140 degs the hesitation was gone.

[1schoir]

Have you checked your air filter for clogging or your air filter box for leaves, debris, etc.? It could be as simple as that.

Try starting the engine from cold with the air filter removed (and the air filter box clean). If it changes the idle behavior, replace the air filter.

Regards, Maurice.

[bustingear]

I have the same problem and have replaced MAF, all coils, all spark plugs, AOS

What else could it be?

[bustingear]

Also the air filter is new !

[bustingear]

Clean the idle air control valve on the left side of the throttle body. It's possible like many things are possible

Sounds like an intake leak. Check all clamps listen for leak. Assembly quality after aos?