Im new to the forum sorry if anyone finds that fact annoying...
I need help with my Z thats driving me a little nuts.
My Z has this sneeze that wont go away,
Ive replaced my distributor rotor, spark plugs, plug wires, adjusted my spark timing and replaced my air flow meter. Nothing seems to make a difference BUT all parts were messed up in one way or another.
Ive been following specs from a haynes manual (spark gap, timing)

After driving the engine smells like charcoal and burning plastic.

My Idle is usually high (1200-1300rpm) when i adjust the throttle screw to idle around 900 and turn off the car, the next time i start it it will be at approx 400. Also during driving I will get Fluctuations of 800 to 1300.

Im at a point where i just feel like throwing parts at it blindly because they all need to be replaced anyways hahah. Does anyone know if these 3 problems could be related? Any Ideas?

Current plan is to replace the horribly old looking Air Regulator, Throttle position sensor and all vacuum lines.

 

Welcome to Zdriver!
Maybe your cat is clogged up causing higher exhaust temps.
I had the same idle problem with my "77. It turned out to be the fast idle for the AC cycleing on off. If I remember it is a blue wire going to the tb. I just disconnected it until I can get the AC working.
It is now time for you to download the Factory Service Manual from www.carfich.com. It's free but it's cool to make a donation.

 

thank you for your time.. I went to the site but its telling me its under construction.
I was forced to drive my Z to work today in the condition its in and found if I keep the RPMs really high when shifting and when starting in first then there is no back fire, smell is still there. Do you know if these problems are related?
Thanks again for your time and help.

 

I just tried it and it's up. btw Tna means temporarily not available. There are many things that can cause your problems. backfiring can be caused by to much fuel. With the fsm you will be able to check everything.

 

It's actually "CARFICHE"

http://carfiche.com/

You can also download the FSM from: www.xenons30.com/reference

I would check / adjust the TPS, and check the water temp sensor (white/yellow square two prong sensor on the thermostat housing).

 

thnx "nismopick" good stuff....
those are 2 things I have on order. In my frusteration yesturday I went to the dealership I used to work at and ordered everything my paycheck could handle, Its a stupid desperate approach, but thats what I did and it is what it is. Thankfully the TPS and water temp sens. were on that list hahah. Thanks for the direction guys.

 

Ouch... you paid dealer cost? I would have ordered them from a local parts store or grab several from a local junk yard....

 

i got them at dealer cost not dealer resale price... used to work there. example- Intake boot AFM to Throttle body EBAY- $50, Nissan- $27

 

Right....

Hopefully you got the TPS for less than $40 and the water temp sensor for less than $14 (parts store prices). Like I said... I would have obtained several from the junk yard for a very small fraction of the cost, since you are replacing them as the method of trouble-shooting. I don't like to spend on unnecessary costs, but that's just me.

 

hahaha yea i saw the same "cost" quotes after i posted it.
I got better deals than my parts store and new parts bring a little ease to my mind and wallet in the future. Thanks again for your help dude! seriously.

 

Ive replaced-
spark plugs (new)
plug wires (new)
distributor cap (new)
distributor rotor (new)
fuel filter (new)
air flow meter (used)
boot from air filter to afm (new)
boot from afm to throttle body (new)
throttle position sensor (new)
coolant temperature sensor (new)
air regulator (new)
fuel regulator (new)
pcv hose

all this crap was in bad condition and needed to be replaced BUT my idle is now not able to be adjusted with the screw, and the intake backfire is still there. Ive owned it for 3 months and havnt really had the pleasure of driving it yet. I dont know if anyone is going to read this, I dont want to post a new thread but I am out of ideas, I noticed someone did a horrible welding job on my exhaust. (they didnt use any sort of reducer to mate the backpipe and downpipe, its like all melted metal weld) I also read "Theramz" mentioning a plugged cat. Ill take it to get fixed and see what happens.

This car is starting to be a horrible buy, because the previous owner made a complete mess out of it.... but its mostly my fault for being the idiot who cant fix it right? lol.... poor pooor Z

 

The exhaust should be the same size as the downpipe all the way back. They may have eliminated the cat which is okay but a big gobby weld might be on the inside too, further choking it off. The blue wire I mentioned goes to that thing under the TB called the throttle chamber.
On the 280z cars the most important tools are your FSM and a multitester. If you read it carefully and step through it you will better understand how she works. Seems overwhelming at first so don't bother to much with the ECU maps for injectors. Just check all sensors.
New parts won't help if they aren't set right. Take your time and you will kill the gremlins.

 

I was just looking at the "throttle chamber" in the FSM. Maybe the sensor for that air system is bad. I remember hearing an audible click when it would idle up or down so I assumed it was AC cycle related. My car is waiting for paint so I can't check it now. I know that after I disconnected it she ran good with no idle changes.Let us know what you find out. Some people come hear, get what they want and go away.

 

thank you for your help man! yea I went through the FSM and kind of did get overwhelmed you are correct. I put the TPS on without any adjustments, might have a problem around that. also I just took a picture of the exhaust so you can get a laugh-
disgusting.jpg?t=1275934781

also got some pics of the engine bay shot from drivers side
messyengine2.jpg?t=1275934470

I cracked the top of the charcoal canister so I am missing one vacuum line, the line went from the canister to the top of the dashpot. I cracked it off yesturday before the picture was taken but the problems existed before that. Also! there are wires jumped together, I bought it with a missing fuel relay? I honestly dont know what belongs there next to the battery.

 

Okay, that jogged my memory. In the manual, EC section it mentions the BCDD valve. Inside the TB there is a hole about 10mm dia. Plug it from the inside. No more fast idle. The charcoal can doesn't matter as long as the line to the engine is not open. I fixed my canister by drilling out the broken one and inserting a short tube and epoxied it in place.
The 2 red wires coming out near the battery are + and - to the ECU. They hook up directly to the battery. Looks like the one to the green jumper is +.
I would stop throwing new parts until I corrected the **** thats for free.

 

the green wire is a horrendous kill switch going to the fuel pump, and you are correct it is + ... Im curious to know what the arched wires are about a foot in front of the battery (towards bumper) something belongs there and I dont know what it is.
Also the fast idle is no longer happening. It is now the opposite- idle starts high, first cold start of the morning, then all day and every run thereafter it is barely hanging on, around 400 -500 RPM Idle and the intake backfire thrives in that condition it occurs on low rpm to acceleration and the lower the rpm the more intense the backfire becomes and the idle adjusting screw will not allow higher rpm... loosening does nothing tightening will make it stall out.

Heres another thing, on lunch I went out to disconnect the wire under the throttle body like you told me, ran the car, still the same. after engine was warmed up I randomly put a drop of water on the exhaust manifold, so im playing with boiling water drops while thinking about complete other things and put a drop between the two injectors shown in the picture. no boil on that port which pulled my thinking in another direction. iinjectorsbadnothot.jpg?t=1275939890
so im not getting the same temperatures out of this port as I am every other one. Injector looks like its in pretty bad shape (the rail is a mess also)

I understand I should probably shut up and follow the charts on the FSM but i keep jumping to these other possibilities and become convinced it must be this or that hahah. Sorry if this is annoying.

p.s. distributor valve seems to be stuck also loll
distributorvalve.jpg?t=1275939890

 

Makes me wonder if your injectors or clogged/leaking...

 

E gad what a mess!. Get a 9 volt battery and some jumper leads. Check each injector including the cold start by pulling the plug and touching the terminals with the +and - from the 9 volt. You should hear them click on and off. No click = no good.
Remove the distributor and spray the guts with PB blaster or Sea Foam penetrant. You should be able to move the breaker plate with your fingers and it should return freely. If not it is probably junk. If OK then use a vacuum gun to test the diaphram, these usually go bad.
Disconnect the cold start valve to see if the backfiring stops, it could be staying or stuck on.
Backfiring in the exhaust means unburned fuel and or late timing.
2 crossed plug wires will run just a little rough but backfire ocasionally even at idle. Recheck your plug wires and firing order.
Check your Thermotime switch per the fsm ohm test.
Spend your money on tools not unnecessary parts.

 

beautiful. Thanks theramz! I will continue diagnostics tonight or tomorrow after work and keep you posted. Im sure this will be a useful lesson to another newbie one day. Although I did get frusterated and threw parts at the car, they were all definitely needed. And you are correct, I could use a timing light lol, all my tools are mostly suspension related.

 

update:
Unplugged cold start injector, seemed to help for a 5 mile drive but started its backfiring and dying out again. Just to clarify its backfire in the INTAKE not exhaust.
going through other forums i stumbled upon this picture


Its some guys float mechanism, my gas gauge does not work so im guessing mine looks similar. Im going to drop the tank and buy a timing light, as well as follow the FSM tune up procedures and first off all the suggestions given on this thread

I will update after all the inspections are done, the forums help has been greatttttly appreciated and i will keep u guys informed.

 

before i start dropping the tank-
I dont think datsun would manufacture a fuel rail and sell every z like this... mine is not normal right? it just seems like an unnecessary mess.. Also in the red and yellow box... what belongs there?


messyengine2-1.jpg?t=1276029481

 

Backfiring through the AFM is like fecebad. I think the dizzy not giving advance has been solved by advancing the timing to far. You really shouldn't drive it like that. Repair or replace the dizzy first. Check the cold start valve by removing it from the manifold and crank the engine (coil disconnected). It should squirt when you crank the engine. Next, do the same with it unplugged, it shouldn't squirt. The wires you have noted are fusible links. They should have plastic covers on them. Not that important. The fuel rail looks stock, it's just be tweaked around by a po/ gremlin.
Be patient and careful so you don't ruin something. We can get you through this, wax on, wax off.

 

I don't remember if you stated the year of your car but here is my '77 in progress. There are some slight differences. I'm guessing yours is a '76. You can make it better and dependable. The only thing new on mine is the thermosat, water temp sensor and thermotime sensor. The engine is a complete rebuilt so I had the advantage of it being on an engine stand.

 

out of money and out of work.

I checked the cold start injector it doesn't squirt at all

The car was built in april of 1977, its a 5 speed, I took a video of the engine bay and rpm gauge while it is running, Im trying to post it now.

 

here is a video of me trying to keep the car at 3000 RPM... I am uploading another video of the back fire which is going to take a while....
http://s756.photobucket.com/albums/x...=LazyZblah.mp4

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