It sounds like either the AFM or TPS to me sense it sounds to be running pretty smoothly.

 

it doesn't idle smoothly at all... im trying to get the other video uploaded its being difficult.. It has a horrible low idle and intake backfire... once i get it past the low rpm acceleration it seems to run fine. the only way i have been able to drive it (the small amount i have) is by keeping the rpms high at the take off and revving it up in between shifts.. watch the new video when i finally get it up here.. I already replaced both tps and afm when i got frustrated a couple weeks ago and just started throwing parts at it. Thanks! ill get it posted soon



... By the way- It WILL rev past 2,800 and this is not a video of the idle. I have just found that if i try to hold around 2,800 i get this strange fluctuation. I want to fix this as well as all the other problems but am hoping it is related to the intake backfire/rough idle and will kick start somebody's memory or whatever. thank you!

 

here is video of the engine idle and a quick over view of the engine.
it starts by showing the horrible exhaust weld, which is probably plugged, then it goes over the engine.
at 00:28 it shows a hose that has a plug in it.
at 00:43 it shows random wiring that goes no where.
00:55 stupid kill switch someone put on the car (positive to fuel pump)
01:20 you can hear the sneeze
01:38 " " "
01:42 I adjust the idle screw and nothing happens


http://s756.photobucket.com/albums/x...kebackfire.mp4

 

It's definitly not firing on all 6. The timing is way to far advanced, firing when the an intake valve is open. That screw is for air mixture not rpm. You could have a dead cyclinder. Pull all the plugs and do a compression test. Use your thumb over the spark plug hole and have someone crank it over. You should have a healty pfft on each one. Those wires go to something behind that plate, probably a bypassed relay.

 

The hose in this pic^^ used to go to the AC

 

compression test was normal, i unplugged the injectorrs and they all clicked with a 9 volt except the cold start... i need to buy a timing light and have someone re-weld that exhaust to get rid of any back pressure, pull the distributor and possibly replace it, WD40 did not fix anything and it seems to be moving freely.

 

the wires under the dash are all a mess also.

 

Another budget test is to rotate the dizzy plate clockwise and hold you finger over the vacuum inlet it should hold position until you let go. If not it's ng.

 

Or just suck on the hose and if you get air its no good as well. Either or lol

 

Hey Friend,
Sounds like you are running on about 4 cylinders (maybe less!). Thanks for the video, that is so helpful! The exhaust weld is doing very little to cause all of this, if you really wonder, remove the muffler and the back flow problem should be about right. The rest of the work and new parts are probably not helping fix this problem, but they are not a bad investment at all. Don't loose any sleep over buying a few hundred dollars worth of important parts. In today's terms we are only talking about a single car payment on a newer Altima!

I have spent hours as of the last few months on my two Z's and had some very similar problems! It had a very simple solution too! You have checked the injectors with a battery, but they need power from the car to work. As with mine, I am guessing that the fuel injector harnesses are shot. On my car they could be cleaned and bent and made to work, but they had to be wiggled and jiggled to get them to contact. I bought a new set of them off of Ebay for about $15 shipped and the car is running well again. I bought an extra one and replaced the harness on the Head Temp Sensor as well. Before you do this, a simple test is just listening with a screwdriver on your ear and then placed on each injector while the car is running. Tick, tick, tick, check until you hear a different sound from one of them and start there.

The injectors may all be working. But you still have "dead" cylinders. Check the wires, check the plugs for cracks, check the distributor cap for cracks/dead spots. If all of that is ok and you still have a problem... If a cylinder is locked up, sometimes pulling the plug wire on and off a couple times while idling will get her back in action. You have checked compression and that is good, so you really don't have much to worry about there. Maybe you should pull of the valve cover and adjust the valves (or at least check them). Any manual will give you instructions or you can find them online. It is really easy, and satisfying when you get them done and correct.

I also put some Seafoam in the oil to clean the valves, you may want to do the same. Finally, the car will need the plugs pulled and cleaned almost every time you work on the EFI. They gum up or get fuel fouled. Sometimes you will have everything else correct and it still will be "off" and you will start pulling more wires, etc. and it will just be fouled plugs from the last time you tried.

I'm not a betting man, but I would put money on the injectors or harnesses being the problem. Give it a go and let me know. I have some more ideas, but lets start there for now.

 

the Z has been parked since my last post..
I've been both frustrated and busy looking for work since i hooked the injectors to the 9 volt. to the injectors.
I just ran the car a second ago. (It fired up better than it has ever started before) I listened to all the injectors with a screwdriver and the one new injector (previous owner installed) is the only one which does not make a clicking noise. All of the harnesses look pretty new for every injector, but at least im getting this narrowed down.
I have not yet done any valve adjusting. Im just writing this small update because this forum is very important to me and if im not writing i feel guilty.
Once again thank you so much for the help. I am planning some tear down time and electrical testing hopefully this weekend!

 

the wiring to injector that made no noise tested out okay. I pulled the injector and cranked the engine with the distributor disconnected and no fuel came out. I noticed the 1st injector is leaking bad, PO had the hose clamped and when I took it off I found the hose is badly cracked. the 2nd and 3rd are seeping and the 4th is silent when I listen to it...
to sum it up I do not approve of the visual condition of any of the injectors.
Does any one know where I can get a set of well rebuilt injectors? I want to just replace all of them. The more new parts I have on the engine the happier I am, Im also afraid of replacing one and watching another go out and then another and so on.
Thanks for the help!

 

inj1.jpg?t=1279084032

injector #1 above


inj3.jpg?t=1279083789

injector #3 above


inj4.jpg?t=1279083793

injector #4 above. This is the new injector that makes no noise when the car is running

NOTE: I have the metal clips off in the pictures they are normally on the car when it was running funny.

 

Here is the best deal I've seen yet. Go to ebay and search "datsun 280z fuel injectors" This guy also has all the hardware so maybe you can make a deal with him. After you start breating again maybe you want to take your 9 volt and search the junkyard.

 

pulled the injectors today.
Here is a picture of the new one I have been talking about that the P.O had installed, pictured next to the older cracked one...

The newest one that was installed is about 1/4" shorter this is not a problem right?


<a href="http://s756.photobucket.com/albums/xx209/BenZ513/?action=view&current=injectordifference.jpg" target="_blank"><img src="http://i756.photobucket.com/albums/xx209/BenZ513/injectordifference.jpg" border="0" alt="Photobucket"></a>

 

The black pintel cap is missing, the reach is short and the shape tells me it' s from a different car. The injectors are color coded for volumn. I think yours are supposed to be green.

 

man i need to do some more research... you are saving my @$$ "theramz".
the 2 new ones i bought are green, (picture came out a little blue) im going to let it sit till i can afford all 6, take off the rest of the rail, and replace every hose and seal. should be all paid for in about 3 weeks?

<a href="http://s756.photobucket.com/albums/xx209/BenZ513/?action=view&current=newinj.jpg" target="_blank"><img src="http://i756.photobucket.com/albums/xx209/BenZ513/newinj.jpg" border="0" alt="Photobucket"></a>

 

Lazy Z have you tried to check the timing chain on it? I'm having similar problems and have done a whole bunch of changes to it but the motor stumbles. Im thinking about checking the timing chain? Think is a good idea?

 

I have much this same problem. How do you know which plug to put on what fuel injector? They are not marked in any way.

 

Does anybody know how to identify which plug goes to what fuel injector/ They are not marked.

 

How do you know which plug goes where on the fuel injectors of an 85 300ZX?

 

Order a new thermotime switch from Nissan. It is located in the thermosrat housing and it's brown in color. That controls the cold start valve. If it's not functioning correctly it will send a signal even when the car is already warmed up and the cold start valve will dribble excess fuel and cause some of the problems you're having. Good luck with it.