XDR

I finished my swap about 2 months ago and have about 200-300 miles on it while working out little bugs. I have a code P0507 and so far have used carb cleaner to look for vacuum leaks (none found) swaped TB with sensors from my 01 LQ4 and replaced the PCV valve. I also plugged the PCV port on the intake and TB and code still registered. Jeep side of vacuum system holds vacuum with my hand pump. Checked torque of all intake manifold bolts and they were fine. EGR is blocked off with freeze plug and there was no sign of leak with carb cleaner.

For fuel system I'm running a return-less fuel rail from a newer 5.3 and have a vented fuel cap to vent fuel tank (code still came up with stock non-vented cap).

Idle is approx 625 (around 900-1000 when cold then it drops after 20-30 seconds). Driving wise there is no high or abnormal idle speed noticed.

Since installing the new intake there is a whistle when slight throttle is applied but wasn't there with stock intake and had code both ways.

VSS is not hooked up to GM ECU as I'm running a Jeep VSS directly to AutoMeter Speedo. Could it be detecting that its higher idle while I'm coasting in gear?

Where do you suggest I look or check next?

gagliano7

I had the same problem. I have a standalone harness with a 1999 5.3 pcm auto trans in a 1992 chevy pickup 5 speed manual. I did a smoke test and fixed my vacuum leaks intake manifold gaskets but I still got that code. Hooked up my vss to my pcm and haven't had the code since. I think since the pcm wasn't seeing speed that it was setting the code thinking car wasn't moving.

XDR

Ok, good info.. that was my thinking on it. Are you using a GM VSS? I know mine operates at a different pulse and different type of pulse.