matthious

ok, i'm running out of things to check/do. i have a 78 280z, fuel injection. it purrs like a kitten at idle, no throttle response. i can slightly blip the throttle to bring the rev's up to move the car in and out of the garage, but that's about it. the only difference changing the timing does is affect the idle. the engine still bogs, and backfires into the induction system when you open the throttle in a normal fashion. once the revs are off idle, there is weak throttle response, but only if you move the accelerator Slowly. it feels/sounds like there is no timing advance, but i don't know what else it could be except the afm. and i don't know how to check if it's good without spending cash i don't have for a new one and putting it in and crossing my fingers.

i've read almost every post on this site about the afm, (there are Lots of them) and still haven't been able to find out two things:
1, when you move the little weight inside the afm while the engine is running, what response is 'i'm working just fine, leave me alone' and what is ' i'm FUBAR, fix or replace me dear Liza'.
2, how do you test, adjust the throttle position switch? it is the little black box on the open end of the intake, correct? is this adjustable on the N/A or just the turbo? I'm N/A.

here's what i've done/checked so far.

drained the 6 yr old gas, replaced the filter, added new gas.
replaced all plugs, wires, rotor, cap, vacuum advance. (old plugs all looked good, no excessive carbon, burning, oil etc)
replaced any vacuum hoses that were dried out/cracked.
checked that check valves in vacuum lines were the right way, (previous owner had replaced a few hoses with blue ones, i guess he wanted them 'pretty'. i just want them leak free)
cleaned every electical connection i could find. lots and lots of corrosion, and cleaning those little harnesses is a pain in the a$$)
cleaned afm, moved wiper track according to the link posted on this site.
seafoam

when i put the afm back in the car, the first time i forgot to plug in the harness, and it wouldn't even start or idle. plugged it in, and it idles, so i think it at least partly works. but how do i know it is functioning correctly throught it's travel? also, it had a zap-strap, cable-tie, tie-wrap, whatever you want to call it where you're from on it, so it had been opened at some time in it's life.

when i unplug the tps, i get no change in idle or throttle response.

when i unplug the injectors one by one, the engine idles rough. i can feel them firing with my fingers, i can also hear ticking, so i'm thinking they are at least firing, but don't know if they are dirty. seafoam is in the tank, from searching this site, thank you.

I have a multi-meter, and will start going through the service manual i downloaded to see if there is anything i can check with that, but at this point i don't know what i'll be looking for. again, from a link posted to one of my previous threads, i think from nismopick. thank you! that is a Huge help!

so, yes i've searched this site,
yes i have read and seen that there are over 300 posts with 'afm' in them,
yes, i've learned more about the afm than i knew before i bought a z,
yes, i've heard to check the afm, throttle position switch,
but no, i don't know how to tell if it's good or bad.
and no, i don't know what else to do.

i would love to get this car drivable, and even more so since i'm faced with a very real possibility that i've burned a valve on my bike, my only mode of transportation.

anything you can post, opinions, links, suggestions, will be read with an open mind and appreciated with all due respect! i do almost all my own work, and will try to fix it before i tow it to a shop.

'if the women don't find you handsome, they should at least find you handy.'-Red Green.

m

hoov100

i would grab a spare working TPS and try it out, if that doesnt solve your problem i would start looking at a new AFM or converting to a z31/MAF setup. one other thing you could inspect is the wiring harness for the AFM, i had a problem once that wouldnt allow me anything past 1/8'th throttle and would backfire and sputter anything above that. i would start checking the actual wire as well.

NismoPick

#1: With the motor running, push the weight lightly clockwise & then counter clockwise. If the rpms increase, or the engine sounds better in one direction or the other, you can adjust the spring that direction.
#2: The TPS indeed is the black rectangular sensor on the throttle body. You adjust it w/ an Ohm meter (should be info in the Haynes / FSM).

Classic sign that someone messed w/ it & prolly screwed it up.

x2 on what Hoov said. Try another TPS.

matthious

Awesome!! thanks for the advice guys! i'll dig into it and let you know what i find.

m

theramz

The fsm has a complete test procedure for the afm and tps. It's easy with the book if you have a multi-testor, impossible without them.

matthious

Matthew is one happy guy!!!

It Runs, with Throttle response!!!!!

so for those of you who may have similar problems, here's what i did after the suggestions from this thread.

i researched and learned everything i could comprehend about the fuel injection system on this car from every source i could get.

i then wrote down the diagnostic/test procedure from the manual for what was similar to what my problem was. i also wrote down how to test the afm/tps since that was the common suggestion. my car is not where my 'puter is, also no printer so i had to make complete notes, and then make sure i could actually read them.

off to the car on my sick sportbike. (not a great start to my day)

pulled the afm, tested according to my notes, test good.

tested the tps, same deal.

scratched my head for a while, stared at the engine.

pulled the harness for the computer, plugged in the afm/tps, started to test the system according to the chart in the manual.(the one i drew in pencil). all tested ok at this point. more head scratching.

tested for continuity in the system. oooopsss!!!! that was supposed to be first, it was on a different page. no continuity in the tps circuit. to the tps.

pulled the harness, again. found a hole in the rotten rubber boot, saw a glimpse of familiar green, tore the boot off, hello broken wire!! broken off about 3/4 inch from the harness.

connected the wire, plugged everything all up, fired up the car. throttle response, just running like sh$t. played with the timing, car has a little lag right off idle, then off she goes. woo-hoooooo!!!!!

back to the afm. someone had played with it. adjusted the wheel in the direction where it ran best when i moved the little weight. a little adjustment here and there, found happy ground, car runs ok. not great, but ok. good for now.

z00000000000mmm!!! off for a drive i go. NICE! except for a slight bog, jumping out of second gear on deceleration, and a tach that doesn't work. I'll take it! For now.

sooooo, next few days it's body work, then emissions, and so-on.

Thank you So Much for your input!!! I'm happy to have a running Z, and to be able to use the 300 bucks i almost put into a new afm for other things the car needs.

m