Quote:

The gas cap will set an evap system leak code indicating that the ecm detected a drop in vacuum within the fuel /vapor system system during it's periodic drive cycle test. Rob's initial post indicated that his check engine was flashing which can only be caused by a hard misfire. I'll bet by flashing he means it comes on stays on until he turns the ignition off, then comes back on when his malfunction(po420) resets the malfunction indicator lamp again. This can happen on older cars unlike newer cars which hold the code until manual reset.
PO420 is a catalyst efficiency code set when the upstream(front)o2 sensor and the downstream(rear of cat)o2 sensor show identical readings indicating no catalyst activity. Rob's complaint of pinging (and,I'm guessing,a lack of power) could be attributed to a partially clogged cat. We don't even know if Rob's vehicle has the 4.6L or the horrendous V-sucks. Rob, if you're out there PM me and we'll talk,you're only a state away.



I understand Paul was just saying the 2 crappy Kia Sportages my friend had,if the cap was too tight or too loose the check engine light would come on and stay on until I reset it in the computer. I have CAN OBD II reader among other tools I need in my trade. Just saying on some cars the stupid gas cap will in fact trigger it.

I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!