codes

I not shore If this will help. But here's the manual for my decoder. http://www.actron.com/publish/2004/06/23/pdf_english_16153.pdf

The engine running codes are different from the engine off codes. The 4 code you got was probably the computer identifer, and 4 means it's a V8.

If you didn't get a 41 when you did the key on, engine off test then the O2 sensors did not set a code.

The goose test is known as the cylinder balance test. It does not necessarily test for lean mixture.

Cylinder balance test:
Warm the car's engine up to normal operating temperature. Use a jumper wire or paper clip to put the computer into test mode. Start the engine and let it go through the normal diagnostic tests, then quickly press the throttle to the floor. The engine RPM should exceed 2500 RPM's for a brief second. The engine RPM's will increase to about 1450-1600 RPM and hold steady. The engine will shut off power to each injector, one at a time. When it has sequenced through all 8 injectors, it will flash 99 for everything OK, or the number of the failing cylinder such as 22 for cylinder #2. Quickly pressing the throttle again up to 2500 RPM’s will cause the test to re-run with smaller qualifying figures. Do it a third time, and if the same cylinder shows up, the cylinder is weak and isn’t putting out power like it should. See the Chilton’s Shop manual for the complete test procedure