ok, heres the deal...its a 76 280 F/I, with the a/c off and the car in neutral, if i step on the gas to bump my rpm's the engine will bog down for a second two ever so slightly....with the a/c on, the engine bogs down to about 3-400rpm's and catches itself before it dies and jumps back up to idol normal again. it does the same thing when im driving and put the clutch in...no biggie cuz i get it in the next gear before it hits 800 rpm's, until i hafta come to a stop. its got new injectors, fuel pump, and airflow meter.... and it doesnt matter if its hot or cold...it does it all the frickin time!!! any ideas would be greatly appreciated...

thankyou

hrm..... ecu?

if u find find the answer to that let me know, my 280's doing the same thing, however i havent replaced what you have. im thinking i may have a vaccum leak somewhere

It's bogging down all the time, moreso with the A/C.

The A/C draws power from the engine, so it makes sense that bogging would be less without it in operation.

I'm not so sure that this is ECU related, I think it's fuel system related.

You've replaced the injectors, fuel pump, and AFM.

What about the fuel filter? (could be all fouled up with crud).

What is the condition of your gas tank? (your sending unit could be clogged with rust).

FWIW.

I don't know about the 280s, but my 260Z has a 'fast idle actuator' that increases the engine revs when the A/C is on. A vacuum hose goes to a relay on the right hand side of the engine bay, the relay opens up a valve when the A/C is on that lets the vacuum through to the actuator. The actuator is just a vacuum driven puller that pulls on the throttle linkage. It is adjustable. I had to fix some vac hoses and adjust the actuator when I got my A/C running again recently.

The 280s might be a bit smarter than the 260s and do things differently.

If this helps, good,

if not, good luck

Eric

True, it's a good idea to look for the common sence things first like a clogged fuel line, filter, bad FPR ect. but Jason isn't off mentioning the E.C.U. as a possibility. Since the Electronic Control Unit is basically the brains of the whole system and computes the info it receives from the AFM and then sends out the signals to the other EFI components to maintain the correct air/fuel mixture, correct length of time the injectors are to stay open ect. so I'd TEST the E.C.U. first before you assume it's OK and rule it out because it very well could be a possible suspect if all the basic things check out good.

Good luck,

ive changed the fuel filter too, sorry, forgot to add that.. and yes, it has one of those vacumm lines attached to the intake maniforld.. but i cant hear any vaccum leaks or anything... will tinker with it tomarrow when its light outside and keep ya posted..

Seafoam time. Sounds to me like you just need to clean out the throttlebody and the intake. Cleaning the intake and valves is easy with Seafoam. To clean the throttle body though, pull it completely remove the rubber that you can and dip it in a can of parts cleaner for 15-20 minutes then scrub with a tooth brush and blow clean with compressed air.

im still tinkerin with this darn thing... will let ya know more tonight

Try this out. Do a little trouble shooting using this EFI Bible. It has helped me more than once. http://www.atlanticz.ca/zclub/techtips/efisystem/280zfuelinjectionbook.pdf

ok...i finally got off my arss and pulled apart the throttle body and gave it a thorough cleaning..and oh lord it was the nastiest thing i have ever seen. sooo, that seems to have cured the problem..however, now i cant get it to idle any lower than about 1000 rpms...oh well, could be worse...thankyou very much to all who gave suggestions...

You should be able to adjust your 1,000 RPM idle with the thumbscrew at this point, or maybe after the car fully warms up, she'll drop out of fast idle mode.

Anyway, congrats for getting another small project done, now onto the next one...