Stumped!
 

I have a 82' 280zx Turbo Automatic.
It revs up fine in N but when it's under load it will only rev up to about 2,000 RPMS and then it will die off. I checked the fuel pump/filter and I checked some electrical but I'm not sure what else would do it. I've been told to check the turbo itself and the compression. The problems started recently when I put in new spark plugs but I'm not sure that's the problem... any ideas?

is it the CHTS on these things if it goes bad it wont rev past 2000?

No it's not bad... at least it shouldn't be. I checked it.

most likely your AFM or TPS.

Well when I "floor" it that's when the car wants to die...

its either too much fuel or not enough, check to make sure your TPS is only contacting the WOT contact at WOT, if thats all good, test your AFM.

Does it try to build boost at all when under load before it starts cutting out? If so maybe the spark gap is a little bit to wide causing the spark to get blown out under boost. Just thinking it might be a possibility since you said it started after you changed the plugs, and that it seemed ok when in neutral (no boost condition).

CHECK timing, AFM, CHTS, TPS, all sensor connections, ecu connections, grounds, check spark plug tips, etc etc etc... all the usual things you do to diagnose a prob. :D

It tries to but then dies off right before it can..

Have you checked these things?

I have checked all of those and replaced the CHTS and TPS and I have cleaned all of the ecu connections and everything else... and I checked all of the spark plugs... nothing seems to be wrong there..

What is the timing set at? What color are the spark plug tips?

Uhh... the timing is set as factory I would guess... and the spark plug tips are once again black.... most of it is black anyways.

time to try a working AFM or do the MAF swap...

so... when I asked if you've checked timing, you really haven't?

It's not the timing, the timing is fine. I just put a new fuel pump in and now it wont even turn over... I hooked a multimeter up to it and everything is hooked up fine, I'm not sure WHAT is wrong with this thing. I tore the dash apart thinking that is was something electrical before this whole fuel pump thing and it looks like someone went and tried to rewire it, everything looked to be okay in that though. I was also thinking that maybe the guy that I bought the spark plugs from may have given me the wrong ones, so I looked that up but that was fine. I re-gaped the spark plugs a little lower than before... sitting at 40 instead of 44... but that also didn't change anything. A friend of mine keeps telling me that if the Turbo is going out or if something is stuck in there then it would cause this problem to happen. The car will rev up just PERFECT in N but whenever it's under load, it doesn't want to go past 2,000. I was going to get a compression test but now I can't even start the car. I was thinking it was something do to with the wires to the fuel pump or maybe something was jammed in the tank itself. I'm really running out of ideas.

Have you checked all your vacuum lines? Make sure your ECU grounds in the engine bay are clean and grounded well, make sure the cables at your battery clips are not loose at the clip or anything.

From what I'm getting is you don't know if the timing is good or not, you're just assuming. Chances are timing is off, and you may be looking at a dead or dieing ignition module. Pull the coil wire from the distributor cap and ground it on the engine and have someone watch it to see if you get spark while cranking. Have you checked your fuel filter?

To do a compression test you don't need the car to turn over.

I know it's not the timing, trust me on that one... and to do a compression test, I would need to take the car to a shop that has a compression tester and without the car being able to move or even start for that fact, I can't do that..... therefore the car WOULD need to be able to start to do a compression check... in my situation anyways. I bought a brand new fuel filter... it's not that. I checked all of my vacuum lines when I first bought the car and bought new ones for the ones that were old/cracked.... the rest of them were fine. The car DID run fine when reved up in N but just not under load... so doesn't the knock out the fact that it could be anything to do with the ECU (just from what I've been told)???

#1... you keep saying it's not the timing, yet you have no idea what the timing is set to... hum, good start.

#2... most parts stores loan out compression testers... unless you can't walk or take another car to your local parts store, there's no reason not to check it.

#3... you've pulled the spark plugs, DO ALL THE TIPS LOOK EXACTLY THE SAME?

#4... AGAIN, (and hopefully the last time I'll have to say this) HAVE YOU CHECKED THE CHTS & AFM??? Just looking at them ISN'T checking them. Check the connections. You can also take off the AFM cover and adjust it.

The CHTS & AFM are the main sensors and are the most likely cause of your prob.

You don't need the car to run to do a compression test... just need to turn over... so yes you can do a compression test... don't think that will help... but you might get lucky... are the new plugs black??? If so, that's to much fuel... BTW... did you check thi timing... ie, the wires??? If you didn't put 2-3 wires on the right plugs... thennnnnn, ... ??? Okay, did the Z start and run good after you put in the new plugs??? If not, just go and get new ones... NGK or ND oooooooooorrrrr... put in the old ones and see... If that doesn't work, then you know it not the plugs, move to step 2)...

my car was doing this, it sits on its face when you floor it. drives pretty normal other wise. i narrowed it down to my AFM / ECU connections. go over ALL of your EFI harness connections, not just checking them, but cleaning them both the plug and the sensor connection points with electrical cleaner and a scraping device, then let them dry, then re-bend all the connectors connection points so you know its all making good contact, and make sure no wires are loose, if so, they could be getting pushed away when you try to plug them in also resulting in a pretty weak connection. also, check your timing, and i would replace your cap rotor plugs and wires if you havent already.

Well if you don't have one I hope you've ordered a Haynes guide, but anyway go here and download the full FSM: http://carfiche.com/

It's not always available, so you'll have to check back every hour or so as the downloads rotate, but eventually it will be. Do that and follow the procedure for checking your car.

dude you may frustrated, but you gotta take a step back, go in one direction, and test the stuff these guys are saying. we all suggest this stuff simply because we have all done it many times b4 with the same problems. there are tons of old threads with exactly the same answers on them here. its usually something simple on these cars. you will win, just knock any chip on the shoulder off, and start over.

The timing is set to 20 degrees. All of the tips look exactly the same, black. The CHTS is new and the AFM is fine, why would the AFM cause this problem only under load? I don't understand how an AFM would cause problems under load normally the AFM would cause problems from IDLE all the way up no matter if it's in gear or not. I pulled each spark plug one by one and the loom separators are all in order and not touched plus this would cause a problem while not under load as well. The car ran fine with the old spark plugs, it started all of this after the new ones were put in. The wires were all checked and everything there is fine. I checked NGK part numbers and I double checked the gap and the wires, everything's fine there. I have started to download the manual so I will go over that and try to get most of my questions answered there. Yes it is a little frustrating but I knew that this would happen... after all a project car is going to be a big project right? I simply LOVE my car, just want to get it back on the road. Thanks for all of your help!

When it dies, does it sputter, buck, make popping sounds through the intake, or does it try to keep going through the rpm band while misfiring? Reseat the ecu connectors a few times, and check for vacuum leaks, the boot from the AFM to the turbo can have cracks. I doubt it's the turbo going bad, or else you'd have a lot of smoke and a lot of odd noises coming from the turbo itself. What's your fuel pressure at?