Reynaldo, thanks for the help

Question

I did as you suggested. Pulled the vac line off the fuel pressure reg, no leak of fuel while running. I did replace all plug wires today. Still has low idle and will stall. Added some injector cleaner to the tank. Any suggestions as to what to look for/at next?

Answer 1

P0300 Random misifre

P0446 Evaporative emission control system vent control circuit malfunction

Exhaust back presssure, would would have to be ruled out, a partial block exhaust would set a low RPM with a random misfire, There are a variety of way of finding exhaust back pressure a vacuum gauge connected to a intake manifold vacuum source, at idle the guage would read 18 to 20 vacuum.. and at a steady 1500 -2000 rpm the vacuum should show 18 - 20 vacuum.. if it less than 18 you would have exhaust back pressure. Another way be to loosen the exhaust flange bolts enough to have a exhuast leak and if engine performance improves , exhaust back pressure would be suspected..such as the catalytic convertor. Another way is to remove the 02 sensor both front upstream before the catalytic , if this way is preffered, you need to have the 02 sensor harness connected and 02 secured, having a disconnected 02 sensor would set a P0300 and rough idle.

 The best way to test for exhaust back pressure is loosen the exhaust flange bolts enough to have a exhaust leak , and test drive for improved perfromance.