Car dies after revving

[johnnyddn]

I have a 1978 FI 280z, the car starts fine but if I give it a quick rev and let go of the gas it stumbles and dies. If I rev it but don't let off the gas pedal entirely (like enough gas to keep it slightly above idle) it will keep running. Right now it is idling at about 800-900 rpm. I pulled the plugs right after it was running for about 20mins and they were dry and I don't see any smoke coming from the tail pipe. The exhuast smells like fuel pretty strong but I don't know if thats a normal Z thing because I've heard of people complaining about the exhaust fumes from Z's before.

[bigoak]

Could be a few things but most likely fuel starvation or timing is off.

1. Check your fuel filter to see if it is clogged. If so, replace it and you may need to clean out the gas tank if it is gunked up.

2. Check timing.

I'll let the FI guys chime in if issues specific to that may be a cause, but these are simple checks and common problems.

[johnnyddn]

Well I raised the Idle to just a hair below 1000 and that seems to have fixed the problem but I just might be covering it up.

[GreenZZZ]

My 240Z did that alot when the throttle shafts in the carb we're leaking sporadically. Before a real fix (aka Z-Therapy carbs), I did what you did and kicked up the idle. Check for vacuum leaks from the air mass sensor to the manifold including your power brake, distributer vacuum advance, etc, etc.

The thinking is the hard rev generates a large vacuum and a leak develops getting air into the cylinder that the air mass sensor isn't measuring and the FI leans out too much causing the stall. Keeping your foot on the throttle keeps enough measured air intake to compensate for the leak and the hard vacuum situation to go away for the leak to seal up.

Wonder if a bad Oxygen or temp sensor would do that as well, but the condition sounds similar to my carb leak.

[sblake01]

Could also be cracks in the boot between the throttle body and the air flow meter (not air mass sensor-these systems aren't that sophisticated). That would cause a vacuum leak that would appear worse on acceleration/deceleration or a quick rev. No oxegen sensor on a 78 but a bad temp sensor would cause a rich fuel mixture once the engiine was warm but you said the plugs were clean and there was no exhaust smoke so you can probably rule that out.