fuel injection 1976 280z Stuttering

[SeanT]

Hello I just bought a 1976 280z, My first z but i have done a lot of research on them. It will start up easily and run cold well at around 800rpm. But once it warms up (the temp gauge is about in the middle.)

It will drop down to 500rpm and stutter. If I give it barley any throttle to bring it to 800 rpm it is fine but if I go up to 1000-1200rpm it will back fire through the intake and exhaust. The plugs are back but not fouled. If I manually control the AFM it will run fine. I also unplugged the connector to the cold start injector but it did not seem to change anything. I am thinking the temperature sensor is the problem. also there might be some vacuum issues because of any dry rot (I plan to re-do all of the vacuum lines).   I do not a lot about how the efi works on these cars except for the basics, and I would like to know how everything works. 

           -Thank you    

[EuroDat]

Hi Sean,

Welcome to the club and congrats on your recent purchase. We all go through some kind of efi problem on these cars, so why should yours be any different. I think its part of the fun of owning these cars. These cars are not that complicated to work on, but you do need to learn some basics about them and ask questions.

The biggest issue for us is we don't have any figures to go on. You manually controlled the AFM. I take it you removed the black plastic cover and pushed it open. If so, that would suggest it is not getting enough fuel. Because you falsly told the ecu it was getting more air. it supplied more fuel. A lot of small things can cause these problems. It could be as simple as bad, corroded connections, but it could also be a sensor.

I would start by downloading the 1980 EFI supplement from the downloads section on this site and go through all the tests in it. You will need a multi meter and some basic knowledge on using it. Don't forget the note the values and avoid giving info like "I did the tests and they were ok" . It should be 210 to 280 and I measured 225.

Check out this site for how to clean efi connections.

http://atlanticz.ca/zclub/techtips/electricalconnections/index.html

[Zed Head]

Someone had a similar problem recently and it was a giant vacuum leak.  I'd find the thread and post a link but I can barely do anything on the site recently, it's very slow.  Good luck.

[Zed Head]

Here it is 

 

[Chickenman]

I think the Internet had a major brain fart. Lots of sites were down last night and this morning. Seems to be fine now...

[gwri8]

23 minutes ago, Chickenman said:

I think the Internet had a major brain fart. Lots of sites were down last night and this morning. Seems to be fine now...

RUSSIA! 

[siteunseen]

32 minutes ago, gwri8 said:

RUSSIA! 

They tied it up with the election in France, which Poot-in lost. Fargin cork soaker.  

[gwri8]

Welcome! You've come to the right place for your S30.

Without knowing any history of your car, hint hint, I'm assuming it has sat for long long time before you got it.  If that is true, the first thing to do is change all your fluids, including any old fuel in the tank.  With the EFI I would go ahead and replace every vacuum hose. They will probably be cracked or rotten. Those are pretty easy.  Do a complete tune up, cap, rotor, plugs and fuel filter. Get all the basic stuff done so you can zero in on whatever ailment is happening.

Also, download the FSM for your 76 here  http://www.classiczcars.com/files/  and get the EFI Bible also.  Very valuable tools that will help you understand the Z.  The great folks here that are going to help you are going to refer to these often and I suggest  you at least be familiar.  The more accurate your description of the problem, The more accurate the replies will be.

Good Luck!

[wheee!]

What production date is your 76? Look in the driver door jamb for the stamped date. The models changed significantly during the production run half way through the year.

[SeanT]

Hey everyone an update on the car. It was last tagged in 2014 so it has not been sitting for to long. The plate in the door jam is missing. I will try to ask the seller if he might have it but I do not think he would have it. I flushed the old gas out and added sea foam to premium which it has been running better the more it runs as well as puttering a new fuel filler in. The fuel pressure was around 38lb is believe. The rotor, cap, and leads all look pretty fresh but the car came with new ones. I have new plugs as well but the ones in the car look pretty new. I already planed on changing all the fluids but have not changed any yet. I tested the AFS by hooking a multi meter to it well it has power and the voltage increased the more it moved counter clock wise. I also want to check the timing on it. I did notice that when I lift the dip stick up that nothing changes in the idle (not when it was surging). I still have not changed the vacuum lines yet, Every thing seems to be not be checked most of the bad line is after the vacuum canister bottle (which is bypassed) and the heater/A.C. controls. Amazon has some regular stuff that around $15 for 50 feet, would that be fine it has a four and a half star rating or should I go a head a buy the silicone stuff for $2 per foot. I also noticed that there was a hose from the radiator to a thing on the intake under the air regulator that looked kinked. I do not know what this is but it might be the problem or part of it cents it seams to happen after the engine heats up.   

[SeanT]

Up date I found that the hose under the intake going into the crank case was deteriorated and cracked on the inside. I replaced it and it is running a lot better i know this thread is dead but anyone who sees this that was the problem. I wound still like to know if what i talked about in the post above will have an influence.

Thank you for every ones help.

[Chickenman]

The kinked hose in the picture above is for water heating of the Auxiliary Air Control valve. Basically your fast idle valve. The kinked hose will not have any effect on the problems you were experiencing. 

 

Not liking those gear type hose clamps on the fuel injection hose though. Those can tear the rubber. Get proper fuel injection clamps that are fully banded and protect the hose.