misbehaving Sport at low speeds

[menostig]

My Sports used to be a real pleasure to drive slowly, but today it wouldn't behave. After a short blast I noticed I couldn't drive at a constant 30mph or 40mph through the limited bits. A steady throttle position resulted in a gradual decay of revs, and with slight extra pedal pressure it would suddenly pickup and of course kick the car faster than desired or expected.

Accelerating away fron stand-still revealed the same hesistancy to pull smoothly until 3000rpm. It would almost die if I tried pulling away in 2nd. It also wouldn't idle nicely.

It did make a lovely noise when engine braking though - with more pops than usual. Flicking between fuel tanks made no odds.

By the way this isn't a bad mannered 600 bhp chevy but a 355 bhp ZZ4 that is usually very smooth and strong at low revs whatever the gear.

Trouble-shooting usually means working out what's changed recently. Well the answer is nothing.. other than I let it sit idle for a month, but have driven it once since without this.

What's going on ?

cheers
Roger.

[gtr-gaz]

Pull the distributor cap off and see what it's like underneath. Mine was so corroded it's a wonder it worked at all!!

Other than that, it could be muck in the fuel filter?

Gary

[steve_D]

The popping on overrun would indicate a lean mix or ignition timing. look for an air leak on the inlet side or a vacuum hose off or split.

Steve

[tuxman]

hi are you running a carb or injection ?

[menostig]

It's a holley 750 carb setup.

All clear in the glass-bulb fuel filter.

Never yet looked in the distributor so something to learn.

cheers
Roger.

[bigmack]

steve_D said:

The popping on overrun would indicate a lean mix or ignition timing. look for an air leak on the inlet side or a vacuum hose off or split. Steve

Is that right Steve? Its been a while since I've had to do much trouble shooting, but I thought I remembered that popping out the exhaust was a rich condition and popping through the intake was a lean condition. I would have thought that the fuel overrun was just that. Too much fuel in the chamber when coming off WOT when decelerating. Maybe I'm wrong though. Eager to hear more about this. I'm fixing to head back to the track in a month with a data logger on the EFI and can study it a little more. Sorry to sidetrack your post menostig. Best of luck with the troubleshooting. I'd check your dizzy cap and plugs. How many miles do you have on the engine?
Cheers!
-Mack