Rough starting - spits, sputters, backfires, but then runs great

[Healeyalt]

I'm having troubles with initial start-ups. This is on a stock 76 FI Z. I crank it for ~ 5 secs and it doesn't fire. After doing this 2 or 3 times, it fires, but sputters and even backfires a little. Then by about the 5th or 6th try, I can keep it going and after a couple of minutes it runs great - very responsive, lots of power, smooth idle, no smoke from the tail pipe, etc. Its' just that initial start-up I'm having trouble with.

Over the Summer I did put quite a few new parts in which did help so that as I mentioned, after initial start-up it runs great; new plugs/wires, distribitor cap/rotor. ignition coil, fuel injectors, fuel filter, and the timimg is on, the AFM checked out OK, and I checked/adjusted the valve lash.

Even though the temperature is still in the 60s around here, could this maybe be my cold start valve, or one of the temperature sensors such as the thermotime or water temp switch, etc?

I appreciate any suggestions regarding what to check and possible replace next.

Thanks

Gary

[madkaw]

Not a FI guy, but sure sounds like the cold start valve, especially if the engine does better when warm. Of course that is probably all tied into the other switches you mentioned. Google EFI BIBLE, might be helpful. Should be some simple OHM tests for testing those switches also- check your FSM

[EuroDat]

The EFI FSM Has a great trouble shooting section. That should help you find the problem.

You can download it on http://www.xenons30.com/files/280zfuelinjectionbook.pdf

oK Injectors has a webpage with step by step instruction to test the bosch Ljetronic injection system

http://www.hiperformancestore.com/Ljetronic.htm

Goodluck

Edited September 28, 2012 by EuroDat