need some help here guys!!

D

driftinmikey

Forum User
ok..I just got my first Z. A 1983 Datsun 280ZX to be right.
But here is my question(s).
The car runs great sittin' still. When driving you can tell that the car is lacking power. It seems that it's missing but I don't think so. Was told that it was a lack of fuel pressure. But...:conf2:
Sometimes when the car wants to you can really get on it and feel the power but then it falls off just a quickly as it came. The car itself only has 179,684 miles on it...really young compared to some that i've seen. And the others really moved!!
I know that the miles on it is young...well maybe not THAT young but still...I really LOVE this car, the power is alomost UN-GODLY!! I mean, I'm used to rotory and four-bangers! So having this much power....:bow:

Also does ANYONE know what the compression supposed to be? was getting a reading of about 150-160 across the board. None was WAY off apart from each other, just about a few...2-4 psi apart.

Other than these the car is still in one piece...well alomost.needs body work but...you know how most people are with "sports cars". THEY JUST DON'T CARE!!

Please somebody help me!! I LOVE THIS CAR MORE THAN MY 1979 MAZDA RX7..and that car is SWWWWWWWWWWWWEEEEEEEEEETTTTTT!!!!
Any help would be great even if it just gets me going in the right direction!
 
Check:

1. Condition of fuel filter - is it clogged with old fuel crud? Nice clean air filter? No bird's nests in there?
2. Get fuel pressure checked and make sure that the regulator is responding to throttle demand - 30psi at idle, rising to 37psi the moment accelerator is pressed.
3. Make sure the ignition timing is correct - 10 degress before TDC for UK market car. Are the plugs, cap, rotor and ignition leads all good? Any loss of spark due to leads touching metal on the way to the plugs?
4. Is the cam to crank timing correct? Has the oil pump / distributor alignment been set correctly? If the head has been removed for any reason in the near past, then check this stuff back to basics - don't assume the person who did it knew how to set it all back up properly...
5. Is the air flow meter responding smoothly? Flap sticky?
6. Manifold air leaks?
7. Throttle flap not opening to full extent?
 
Just changed fitler to brand new one.
Set timing to correct spec and car runs "off", so set timing to what i know.
Got brand new cap, rotor, plugs, and wires.
Motor has never been apart.
But i didn't think about the rest..#2,5,6,and 7.
Thanks alot for the help...i've had no help from anybody here at shops. And well...you know how MOST shops are...
But again thanks!!!!
 
Also..when you metion manifold air leaks..You mean exhaust leak at manifold?
As for the rest,
Air filter been replaced with performance filter as with fuel filter.
Fuel pressure is great. I tried to block line with finger and can't.
I can't even pinch the line my with hand!

As with fuel regulator here is a real problem that I noticed.
99% of cars when you unplug the regulator the car should stop running.
Mine doesn't..it runs better. I replaced regulator with a new one. And still have same problem. When pluged up the car response is better at the lower end, but top end (2000-red-line) car stubbles badly. When unpluged bottom end is slow but car revs to the moon and back. Note this is all sittin' still. When driving, car acts almost the same with a little more stubbling. But only as so much to notice.

The mass air flow meter is working and flap not sticky, as with the throttle body. Not sticking..
But any help in the right direction would be greatful. Even if it's something I might of over looked. But again THANKS!!! :))
 
Set timing to correct spec and car runs "off", so set timing to what i know.
Click to expand...

This statement makes me suspect you should go back to basics on cam timing and oil pump / distributor installation despite believing motor has not been apart.

Have you had a fuel pressure gauge in line to actually check fuel pressure behaviour? Too much pressure could be as bad as too little... Your observation of behaviour when fuel vac line is unplugged is correct - this increases fuel pressure and is the same effect as opening the throttle which drops manifold vacuum to zero.

An inlet manifold air leak would make the motor run lean under load - more air being drawn in than required.
 
ok..I looked at the car today and went down the list you posted. I do believe that timing was a little off. But not much 2-3 degrees off. But just enough to make it run bad. But as for the intake manifold I don't believe that it leaks. But as for the exhaust..lol..on the 6th cylinder the back bolt(closest to the fire wall) it stripped on the head. the previous owner didn't know that it was an aluminum head.:unsure:
so...But I am in the process of fixing that. I think that it may have a profound affect on the car.

But as for fuel pressure. When you turn the key you can hear the fuel pump cut on and then shortly, hear it cut off when it builds pressure. So pressure "should" be fine, but will check tomm.

Now I may have not noted but the car sitting still. Will rev fine. Take off is ok till upper rpm, 2500-4000, 1st to 2nd gear. then car will studder then pick up again then studder. But most of the time she'll just pick up and haul ass.:D She'll go fine at 50-55 mph in 5th. But came up to a hill...you guessed it..2nd to 3rd gear. :mad:
So i'm guessin that it is a bunch of small things that are causing ONE BIG PROBLEM!

But again.. thanks..I'm kinda new to the Z-sport so any help is greatful.
 
Had a similar problem on mine a few years back, mine had a very simple solution tho, A new set of sparkplugs cured the power loss
 
Thats what I thought..So out came the money.
Plugs, wires, cap, rotor button, and upgrade gas to mid grade(like I always use). Even tried new coil. Still no improvement.:mad:
The car, for some odd reason, will run great..sittin' still..Under load car seems to skip and studder, then pick up..(note-all this is with the pressure regulator UNPLUGED)... Plugged up car has problem running. At idle seems normal, give it gas and it stubbles. Now I do believe that I have a vac. leak somewhere on the intake. But I've checked every hose and no luck. I even went as so far as to unplug PVC valve from throttle tube (before the throttle body) and car will idle badly, then die. Almost like normal car would do.
When I unplugged the carcoal purge canister on the car, ran ok ,as long as the regulator was hooked up. So I got to have a vac. problem. :conf2:

Every shop here in USA want to charge me just to look at it. NOT FIX! :mad:

So I am almost at a loss here. I thought that I got a great car for only $500. But seems like a little problem is just making me have second thoughts. I don't want to get rid of it. But...if this problem continues.. may have too.
 
You'll get to the bottom of it, you're making progress eliminating potential problems already! Get that manifold leak sealed and then continue on, it'll be worth it, you seem very happy when it works :)
 
Alright guys..may have came across some of the problem(s). It's a vac leak some where...just where is the question. I really want to thank you all for the help in the right direction. I plan on checking the computer on the car to see if that says ANYTHING. But I hope to fix it real soon.

So far the car will accerate VERY quickly.:D ...never a dull moment till the car spits or studders. But I plan on keeping it for a bit longer. I just found out that Datsun/Nissan don't make the inline 6 anymore ..soo...I got one of the last before they moved on to the 300z. Gotta keep a classic!!!

Again thanks guys...if I have any more problems about this car ..THIS IS THE PLACE THAT I'LL COME TO!!!
 
Thanks...!!! Really look forward to fixin' this car...
So far this car (when it wants to) will just "kick in" and go. I've never drove a car like this before and I must say...WOW:bow: ...

As I said before though, I think that the fuel injectors or something around that is the problem. But thats for a day that it isn't raining..
 
If its yer injecters might have a new set that might interest you,it will probably turn out to be something right stupid,it normally is,best of luck
 
You have a set of injectors? If so, how much for them?...what kind, proformance, OEM?
I have to wait for it to quit raining here so I can check them...But as soon as it stops, I just got the wiring diagram printed off so I can check EVERYTHING. Also, I got the injector troubleshooting guide from a guy here...MUCH thanks to him. As I am sure to find the problem is the injectors.
 
Oh, almost forgot. I did have vac. leak. Fixed it and car still stubbles little bit. Can def. tell that injectors are clogged really bad. Car sometimes picks up and then suddenly falls off again. Took it on a drive yesterday, and car will go real good above 3000 rpm..But as soon as it drops below that it takes a min to pick up again. But then it goes better after a min of driving like that and seems like it cuts out and feels like no fuel is there then it screams again.. So I think that injectors have bad connection and clogged. The car sat for about 2 years before I found it. Guys never worked on it when they got it...So I got a little bit of trail and error time on my hands.
 
Dont know if its been mentioned but is your petrol clean,i know that injecters wear over time so it could be them i will have to check if they r suitable for your zx as they were intended for my throttle bodies,brought 2 sets by mistake,but let me know if it is them
 
I'm pretty sure that it is them..The car will run great for a moment then cut out..But soon as you let up off the gas for a sec the car will pick up and run. So I do beleive that its' them...
 
ive tried injecter cleaner before in one of my cars,waste of time,turned out to be something else but still worth a go rather than keep spending money on trying to eliminate things
 
status said:
ive tried injecter cleaner before in one of my cars,waste of time,turned out to be something else but still worth a go rather than keep spending money on trying to eliminate things
Click to expand...

It's ever likely to be a waste of time if it turned out to be something else:D but I've had good results on a number of cars especially when getting thro the MOT emissions test.
 
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