Vacuum leak detector...works well

[weq92f]

.

So, been chasing a cold start idle and overall idle quality problem for a while now. I tried replacing and calibrating the IAC valve, adding a 1" spacer, mucking with physical blade adjustments and software parameter adjustment (AFR, idle target) to no avail.

Continuing this effort, I employed a pressurized smoke machine to look for vacuum leaks and disassembled my throttle body for inspection and cleaning. The cleaning didn't seem to do anything that I could make out as the unit is not too crusty but went through the steps anyway.

With the smoke tool, I found massive leaks on both sides at the rear of the mounting flange. Also noted smoke seeping from the very front of the flange. After some research, determined that my intake...Edelbrock 2161, is known to leak when using a square bore carb (my tbi is square bore). Edelbrock came out with a carb adapter plate (20 bucks) that makes this go away. I picked up the plate, installed it and now have no leaks.

The first cold start after this was 50% less bad and subsequent warm starts also seemed to be better. Overall idle quality is much improved. My suspicion is that with the vacuum leaks, the system was dumping more fuel and learned to continue doing so (fuel maps were richened up driving with the leaks). Now that the leaks are gone, I'm running rich. This should self adjust going forward and so I expect things to continue to improve.

Need to complete about 4 more cold starts and do some stop and go driving with more warm starts in order for it to adjust.

-Kevin