[zeroziilch]

Hey there, I have a 1983 datsun 280zx non turbo with manual transmission.

So I brought my car into a shop to fix the input shaft bearing, we openned up the transmission, found the bad input shaft bearing, and found some broken/damaged gears in the gearbox, I decided to go with a rebuilt transmission, found a good price, shipped it out and had it done.

Now I get my car back and the thing is a total junk car, I don't think these mechanics know what their really doing. When I dropped off the car, the car was running crazy good, only thing was the sound from the input shaft bearing. I recently had some work done at a better shop and it was clean as a whistle, never was better so I'm sure it's something these new guys did and dropped the ball.

The new shop said it was running bad and needed a "tune up" after installing the transmission. I think they reconnected some stuff badly because now the engine is running rich with fuel, its misfiring, and theres black smoke out the tailpipe. The new spark plugs are completely black. The engine is also very shaky while running. This was neeever an issue before.

Previously I did have a vacuum leak issue that only would occur only on long road trips of 800 miles or more but once the car was running past 2nd gear it would go away. To combat this I would run extra fuel at idle so it never went to the bottom of the guage on the digital dash and the issue would stop after a short while.

Now the car cannot idle at all, everytime I hit the breaks and take the foot off the gas the engine dies and has to be restarted again.

I have a new AFM boot I'm going to try and replace and I have some new vacuum hoses I can try out hopefully to rule out any vacuum leak.

It seems the main concensus online I see is to check the o2 sensor, the thermotime sensor, the fuel pressure, and check for a vacuum leak.

My good mechanic whom I trust is also concerned about the firing order of the spark plugs since the new guys rewired that as well.

Any suggestions would be greatly appreciated.

 

[zeroziilch]

Additionally for the tune up they replaced the coil, and looks like new fuel injector hoses and new spark plugs.

I've had a new fuel pump and fuel injector hoses installed a few years back and should still be good. I had a new thermotimer sensor installed a few years ago. New rebuilt ECU not too long ago. I dunno if that helps at all.

 

[steve240Z73]

Well, firing order is easy. 1-5-3-6-2-4 CCW. The #1 plug should be just a little before 12 o'clock as 12 points toward the radiator.

Next, take all of the parts out of the parts cannon and fill the cannon with cement. No, don't take parts off your car. Just stop throwing parts at it. It's not working.

See if your good mechanic will use the factory service manual to diagnose. You can download it from here or here. If your good mechanic doesn't want to use it, find a mechanic who will use it to diagnose the car.

 

[bonfire79]

Okay.... all these guys that have been "handling" your Z sound like total clowns. (except for maybe your good mechanic) it's not that I think mechanics are clowns, its just that many mechanics now either won't work on your old car, don't know how to work on it, or simply don't want to work on it without trying to replace anything and everything to make $$$.
it's very sad. if you ever take it in to a shop and they can't figure out how to open the hood, get in your car and run!

you took it in for a transmission issue, and they start messing around with the engine instead. now it runs like crap. when they drop the transmission, there is absolutely no need to mess around with the engine or anything on it.
they just needed to drop the tranny and see what the problem was. and of course they then said the engine needed a tune-up... clowns.

if you want a shop to work on your car, its best to take it to a place that specializes in Nissans/Datsuns (not dealerships)
or a dedicated Z shop if you can find one. where are you located, btw?
there are several Z car clubs in most states that may be able to help you too, at least give you some guidance. and get the the FSM as Steve has mentioned^^^^^; it is your best friend in working on your car and doing troubleshooting. It tells you exactly how every single system works and how to troubleshoot those systems.

I'm sorry you have to go through this with these guys. that's a bummer. but if you look around, you can find a guy who is competent and willing to work on your car. and if you feel up to it, you can start learning how to work on it yourself.... starting with the Factory Service Manual.

Cheers,

Bon

 

[kickstand80]

I kind of had the same thing happen to my 81. I replaced the rear trans mount and afterward the car ran like absolute poo. The boot between the AFM and the throttle body came off when the engine tilted and the plug for the Coolant Head Temperature Sensor (CHTS) came off. Your 280 is 50 years old. All of the engine connectors will be corroded and probably broken and dont lock correctly. They will need to be replace with the new style Bosch EV1 quick disconnect style. Many places to get these in a kit do do the entire engine. This will make your relationship better with your Z so much better.
So......Make sure the electrical connection and boot for the AFM and the plug for the CHTS are still connected. The CHTS is on the passenger side screwed into the head between plug 5 & 6 (cylinders are numbered from front to back 1-6). The CHTS is THE most important sensor on your engine. Also make sure that the electrical connectors are clean and free of corrosion.
Most "good" mechanics these days rely on the ability to hook up their diagnostic scan tool to tell them what the issue is. Guess what, no OBD on your car. Your mechanic needs to be an "old school" mechanic to work on these cars.
When I purchased my 1983, it was a non-runner that had been in 2 shops for 13 months. Previous Owner spent over 8000.00 and never got the car to run correct. After I purchased the car I spent weeks of checking and re-checking using the FSM Diagnostic Procedure, it came down to the ECU, just like the procedure says. Lesson is that if you don't have the FSM you will get nowhere and spend lotsa $$$$$$$$$$$$$$$$$$$.
Get the FSM free here Factory Service Manual Free Download.

 

[bonfire79]

Kickstand, you're right about those engine plug connectors being more friendly. the stock nissan ones are always such a pain trying to get those stupid metal clips off lol

and also the CHTS, being the most important sensor, that when gone bad, makes things run so crappy.... but thankfully the designers put it where you can access it with supreme ease
unlike my two Z31's that I used to have.... the sensor is brilliantly installed behind the front timing belt cover, and you have to remove all that crap just to get to the stupid thing.

we got it so much easier on the 280zx

Bon

 

[mydooris4]

I agree 100%, all the symptoms sound like a CHTS and it's really easy to disconnect accidentally. Especially if the metal clip is broken off like on my fuel injectors. The plastic gets brittle and the edge the clip grabs breaks off

 

[zeroziilch]

I live in the San Francisco bay area, know of any around here? Seems like a semi popular enthusiast car, I've seen a few around including my make and model

Thanks for all the input eveyone!

 

[steve240Z73]

You could reach out to Z Car Garage in San Jose. Rob Fuller knows his way around Z cars.

 

[zeroziilch]

Looks like a fuel pressure regulator needs to be replaced but cant find any oem parts online, or can I just use a universal one?

 

[steve240Z73]

Looks like a fuel pressure regulator needs to be replaced but cant find any oem parts online, or can I just use a universal one?

280zx fuel pressure regulator replacement
Most universal FPRs would have to be modified to work on your fuel rail.
On the other hand, why do you think you need a new FPR?

 

[zeroziilch]

They replaced the 02 sensor and fixed the idle issue but both mechanics are insisting the fuel pressure regulator needs to be replaced. You think thats a mistake? I told them to check the CHTS

 

[zeroziilch]

Would anyone know what the fuel pressure specifications are for the 1983 non turbo datsun 280zx 2+2? I'm looking in the FSM but can't find it. Is it 30psi idle and 37psi at full throttle?

 

[steve240Z73]

EF & EC-51

 

[zeroziilch]

Wasn't the fuel regulator anyways, I heard those issues go away if you rev the engine. Turned out to be the AFM needs to be replaced.

Lucked out and a lady with the same car and model year came into the shop and we swapped some parts and figured it out.

Now the real question is, why would the AFM go out if they were working on the transmission?? Bad luck on their part or malpractice you think?

 

[bonfire79]

Wasn't the fuel regulator anyways, I heard those issues go away if you rev the engine. Turned out to be the AFM needs to be replaced.

Lucked out and a lady with the same car and model year came into the shop and we swapped some parts and figured it out.

Now the real question is, why would the AFM go out if they were working on the transmission?? Bad luck on their part or malpractice you think?

it wouldn't. AFM and gear transmission have absolutely nothing to do with each other. they don't connect or work together in any way... tranny's job is transfer power back to the rear wheels in a process of changing gears at certain speeds. AFM simply allows measured air to enter the engine to begin the combustion process.

it's simple really. mechanics who aren't familiar with working on an old Z car with a Bosch L-jetronic fuel management system which includes the air intake system (Air flow meter). unless they removed it and accidently dropped it on the floor and somehow damaged the pentiometer board, or not installing it correctly by not having the air boots secured.

its also possible that these guys knew what they were doing and were also aware that the air flow meters for these cars are still available from Nissan for $400+ and that is something they can always add on to the bill and would probably be happy to do so $$$

they only way to really know if the AFM is bad is by properly troubleshooting it via the factory service manual.

Bon

 

[pilgrim]

they only way to really know if the AFM is bad is by properly troubleshooting it via the factory service manual.

Bon

And that is what you need to know.