I'm am to witts end, and don't even know where to start, but here it goes.

1995, Z28 Convertible with 58,000 miles. Seems that car has gotten harder to start as it has got colder, however could be coincidental. When I turn it over cold it backfires through the intake and makes the air filter smell burnt also diesels for a brief period and a small amount of white smoke comes out exhast. It has been doing this for a while When the weather was warmer it would start but had to hold the pedal to the floor to clear and crank approx 20 seconds. Once it was warm could drive it around all day and it would start fine and drive perfectly.

I have replaced the fuel pump, fuel pressure regulator, checked injectors for leaks, replaced the temp sending unit (the one in the water pump), replaced fuel filter, new map sensor, cleaned the egr valve, new plugs, wires, opti spark II, and new coil. Before and after I replaced the fuel pump and pressure regulator. I perfomed a fuel pressure test, with key on but not running. I got 48 psi however with both pumps the pressure drops off to 20 psi within 3 seconds. Is this normal?

 

Did you scan for codes? Fuel pressure should slowly drop, not instantly. What pumps are you using?

Sent from my LG-LS860 using Tapatalk