ZCar Forum banner

Status
Not open for further replies.
1 - 15 of 15 Posts

·
Registered
Joined
·
107,695 Posts
Discussion Starter #1
I have an 81 280zxt, I just swapped the engine cause the turbo was shot, the engine starts and runs fine below 2000 rpm, if I try to rev above that, it immediatly drops 500 rpm down to 1500, then goes back up right away, and keeps on doing this. All of the vaccuum lines are connected and the only loose wire is the one beside the coil... the little capacitor, the wire pulled out from the bottom and I can't find it =). There is a new fuel filter on it. The car was sitting for about a year in an underground parking lot, could there be a problem with old fuel? I filled it half full with supreme gas, so there is very little old gas in it, please help, thanks
 

·
Registered
Joined
·
107,695 Posts
Discussion Starter #2
I know this might sound really basic, but...

..but mine did the same thing and then I noticed the alternator belt was loose. I guess it couldn't provide enough spark for the engine to rev high. You might want to have the airflow metre checked out too. Just a suggestion...
Best of luck.
Chris
 

·
Registered
Joined
·
107,695 Posts
Discussion Starter #3
Re: I know this might sound really basic, but...

> ..but mine did the same thing and then I
> noticed the alternator belt was loose. I
> guess it couldn't provide enough spark for
> the engine to rev high. You might want to
> have the airflow metre checked out too. Just
> a suggestion...
> Best of luck.
> Chris

Thanks, I tried it,
I don't know if this will work, but I hooked up the battery charger and put it on boost, which is about 14v I think, and rev'ed the car up, and it still does the same thing... Or do I need to do an actuall load test on the alternator?
 

·
Registered
Joined
·
81 Posts
Re: I know this might sound really basic, but...

> .......And i had the air fuel mixture sensore changed and it ran fine. Might have it checked. also look at the injector connectors they might be lose
 

·
Registered
Joined
·
107,695 Posts
Discussion Starter #5
Re: I know this might sound really basic, but...

I'm no expert at alternators, but the easiest way to check it is to look at your volt metre. Is it reading 14 when the car is running? what happens to the volt metre when you hit the gas? You said you changed the fuel filter. My friend's dad had the same problem with his audi. It turned out to be the fuel filter even though it was brand new. Apparantly, there was a lot of junk in the tank so it clogged it up right away. ANother problem might be the air filter or intake. Maybe its clogged. One final suggestion is that it might be the distributor. Perhaps it needs a new rotor. Of course, these are all just brainstorms, so I apologize if this is all old to you.
Best of luck
Chris
 

·
Registered
Joined
·
107,695 Posts
Discussion Starter #6
Re: I know this might sound really basic, but...

Today I'll do a load test on the alternator while it is accelerating, some other things that this car has: new k&n, tko 2000 injector cleaner in tank, new cap & rotor, new bosch plugs. Before I ran the engine I put a can on air intake cleaner through the intake. Maybe I'll try to drain the gas tank and see what kind of ugly stuff comes out.. Could it be the fuel pump? cause it gets louder when you start to accel, not really loud but that humming they make, and then when it gets to about a 1000 rpm it stays constant.. Should I check fuel presure? Thanks for your suggestions I will go right now and try it out.

> I'm no expert at alternators, but the
> easiest way to check it is to look at your
> volt metre. Is it reading 14 when the car is
> running? what happens to the volt metre when
> you hit the gas? You said you changed the
> fuel filter. My friend's dad had the same
> problem with his audi. It turned out to be
> the fuel filter even though it was brand
> new. Apparantly, there was a lot of junk in
> the tank so it clogged it up right away.
> ANother problem might be the air filter or
> intake. Maybe its clogged. One final
> suggestion is that it might be the
> distributor. Perhaps it needs a new rotor.
> Of course, these are all just brainstorms,
> so I apologize if this is all old to you.
> Best of luck
> Chris
 

·
Registered
Joined
·
107,695 Posts
Discussion Starter #7
Try this, too--it fixed mine

Had the same problem with my '81 n/a. Tried many of the same things that you have, then re-adjusted the throttle position sensor and presto! The procedure to adjust this sensor is in your Haynes manual, and is pretty simple (all you need is a screwdriver and voltmeter). Hope this helps!
 

·
Registered
Joined
·
107,695 Posts
Discussion Starter #8
I know I got an older Z but once EFI, always EFI so... sounds like the throttle pos switch on the throttle body, maybe adjustments needed or the connection is foul , had the same problem when I washed my engine came out to be water in the plug cleaned , and all is fine. Goodluck.
Stan
 

·
Registered
Joined
·
107,695 Posts
Discussion Starter #9
The car should run fine with the battery fully charged, even if the alternator isn't working. I would check throttle pos. sensor, and all of rhe connections related to the F/I. Also check fuel pressure.
 

·
Registered
Joined
·
107,695 Posts
Discussion Starter #10
> The car should run fine with the battery
> fully charged, even if the alternator isn't
> working. I would check throttle pos. sensor,
> and all of rhe connections related to the
> F/I. Also check fuel pressure.
I Had Same Problem As Stan Washed Motor And Got TPS Wet So It IS Most Likely That Good Luck
 

·
Registered
Joined
·
107,695 Posts
Discussion Starter #11
clean computer pins

Unplug and clean your computer contacts real good with some contact spray. Be careful not to bend the pins. I had a similar problem with one of my Z's, after the shop had it a month they figured it out. Quick test would be to remove the kick panel so you can get to the computer, then try driving it or revving it up in neutral, when it starts to bog down wiggle the wires on the computer with your foot or hand and see if it clears up.

Just a guess
David
 

·
Registered
Joined
·
107,695 Posts
Discussion Starter #12
> The car should run fine with the battery
> fully charged, even if the alternator isn't
> working. I would check throttle pos. sensor,
> and all of rhe connections related to the
> F/I. Also check fuel pressure.

I had the same problem with my '83 Turbo, but only after I washed the engine. Turns out there was a crack in the throttle position sensor boot, an since the connector faces up, it just filled with water. Unplugged it, soaked up water, hit it with the heat gun and good as new. I then taped the crack in the boot, no problems since. Good luck
 

·
Registered
Joined
·
107,695 Posts
Discussion Starter #13
> I have an 81 280zxt, I just swapped the
> engine cause the turbo was shot, the engine
> starts and runs fine below 2000 rpm, if I
> try to rev above that, it immediatly drops
> 500 rpm down to 1500, then goes back up
> right away, and keeps on doing this. All of
> the vaccuum lines are connected and the only

I had an 83 turbo that did the exact same thing. Check the fuel pressure
Pinch the fuel return line after the injectors. Be careful not to cut it, but
pinch it closed. If this helps your problem then it is the fuel pump, filter, or fuel
pressure regulator...

Eric
 

·
Registered
Joined
·
107,695 Posts
Discussion Starter #14
Fixed!

Well I've tried most of your sugestions and I found the throttle pos sensor wasn't showing any continuity, so it took one off my old engine and now I can rev it up, the only prob is that the hanes manual isn't very clear on exactly how to position the sensor. Now I have another problem.... As soon as I start to crank the engine, as soon as there is any load on the starter, eg: a cylinder comes up on compression, the pinion retracts and spins free, so I can't get the engine cranking long enough to get it started, eventually it hooks up long enough to start the thing, but it takes quite a while. I know that the solonoid isn't the problem cause it has a brand new one on it.
Could it be a problem with the actual starter motor? I am almost tempted to put a new starter in it. Hopefully this will be the last hurdle to get over, besides needing a new timing chain, to get this thing on the road. And thanks again to everyone for your help!
 

·
Registered
Joined
·
107,695 Posts
Discussion Starter #15
AIRFLOW Meter

> Well I've tried most of your sugestions and
> I found the throttle pos sensor wasn't
> showing any continuity, so it took one off
> my old engine and now I can rev it up, the
> only prob is that the hanes manual isn't
> very clear on exactly how to position the
> sensor. Now I have another problem.... As
> soon as I start to crank the engine, as soon
> as there is any load on the starter, eg: a
> cylinder comes up on compression, the pinion
> retracts and spins free, so I can't get the
> engine cranking long enough to get it
> started, eventually it hooks up long enough
> to start the thing, but it takes quite a
> while. I know that the solonoid isn't the
> problem cause it has a brand new one on it.
> Could it be a problem with the actual
> starter motor? I am almost tempted to put a
> new starter in it. Hopefully this will be
> the last hurdle to get over, besides needing
> a new timing chain, to get this thing on the
> road. And thanks again to everyone for your
> help!

Hi,

If your problem is fixed, that is fine. I just want to share my problem wiht you all. I have this kind of problem last time, nomatter how hard I step on the accelerator, my rev just went to 2000 and then go back down and up again.
I bring my 83zx to a nearest workshop (I can't go fast - rev must be below 2000) and the problem was with the AIRFLOW meter. So the mechanic open the airflow meter and clean it and it working back again.
 
1 - 15 of 15 Posts
Status
Not open for further replies.
Top