rhettman360

Hey y'all. So I just bought a 88 300zx 2+2 na with an automatic transmission and I've since replaced the alternator. Ever since I've gotten it I've had a rough idle and extremely poor performance in first and second gear. It feels like I lose all power around 2k rpm. Also, I'm getting terrible mileage for what my route is. I'm more used to working on Chevy motors from the 70s so this is kinda out of my comfort zone. So I'm reaching out to the community for some help. Thanks!

zxguy1986

Welcome to ZDriver!

Maybe it will surprise you that the previous owner didn't do the regular maintenance that was required before he sold you that Z. Maybe it won't. But, guess what. You have some catching up to do on regular maintenance. Not to worry. That Z is a real find when you finally get her running right. She will return your work on her in spades and then some. Just a great ride, unique, special. There's nothing like a Z31. ANd you obviously like cars - so you should be cool with this stuff.

Check out XenonZ31 Reference and download a freebie factory service manual (FSM) and other cool docs which may help you. Your FSM has a bunch of inspection and troubleshooting pages which are easy to follow. See if you can locate your symptoms and what the FSM suggests by way of troubleshooting. Take your time and get familiar with that Z. Up close and personal is the route.

Your Z31 has a number of sensors which should be checked for correct operation and replaced if failed. Especially check out cylinder head temp sensor (CHTS), O2 sensor, crank angle sensor (CAS) and throttle position sensor (TPS), just to get going. Also check your fuel pressure at the injectors - and the two solenoids on your air regulator. Use your FSM to locate them via the diagrams - and a multimeter will come in handy for checking out all the above. And check plug wires for jumping spark and for solid connections at your plugs.

Your new alternator and battery system should be putting out 14+ volts - and no less - all the time. Check that out. Z31's electronics don't run right with lower voltage from the charging system. Check your cables and connections for clean and solid.

There is a procedure in your FSM for running a diagnostic at your ECU/ECCS. It's an early computer (very) which kinda points you in the direction of a problem rather than pinpointing the exact issue - but it may be throwing out a code or two that you can check out. The codes are like good hints. Check out FSM Sec EF&EC-61 to get started with that.

Report back with what you find for your first round results. Our Z31 pros here will have other input for you, sooner or later. Let's get that great Z back on the road and running great.

Thanks and welcome again Post some pics for us when you get a chance.

86tcoupe

Was it running good before the alternator swap?
It is hard to know by your description but a fuel problem comes to mind
bad/ old gas , weak pressure backfiring ?, or a dead/ weak cly ,
really rich out the exhaust ?
I agree with zxguy's post but I like to Try the simple solutions 1st
By weak in 1st and 2nd you mean it does okay in 3rd / Drive?
hows it rev in P ?
Sure it is the right alt ? same pins wiring ?
these OBD 1 cars were not fun to diagnose MFI ,most are gone in the scrap yard but the Z's to good for that . it is hard to find a pro tech that wants to waste hours of time to do what he can in minutes with a very good scan tool w/ live data.

rhettman360

Thank you for your replies. I will go ahead and diagnose the sensors and get back to you.
I'll try to describe it a bit better. If feels like the car just goes limp at 3000 in first and second. Sorta like the clutch partially engages. I have acceleration up until that point but when I hit 3000 all it does is rev and the acceleration lessens. I've never owned or been in a 300zx before so I don't know if that's typical of the automatics. I assume that I should be getting more acceleration out of an 80s sports car. Once it shifts into third I have no problem getting up to speed. But usually it takes me around 5-7 seconds of babying the throttle to get it up to 25-30 (my speed sensor is off). At this point it shifts into third. Put its almost embarrassing climbing the hills around where I live. It takes me around 10 seconds to get into third.
I'm pretty sure its the right alternator. That and I had the problem before anyways. It doesn't run rich, at least as far as I can smell/see. No backfire, and the gas is premium from a recent refill.
It also revs fine in P.
Again thanks guys!

rhettman360

And once it is light again I will post some pics.

rhettman360

Alright I decided to take a quick look at my engine bay before the sun disappeared. I took pictures with my crappy phone camera. I'm missing a few hoses, and there are quite a few wires not plugged into anything. Looks like I inherited some ghetto wiring... :P

Link to pics here

86tcoupe

I'd say you have some burnt/ worn clutches by the descriptions . not a engine problem or mostly a trans. maybe it was towed improperly
hows the trans fluid , black-ish and smells burnt ? fluid level ?
torque converters will drain halfway over a long period and could have air bubbles

zxguy1986

And take your time. Give yourself the time to figure it all out. When that Z is running right, you will be impressed and happy with it. But give yourself the space you need to do it right. No hurry.

To post photos right here, sign in, click Post Reply, write your reply, click on the little paper clip to the right of the smiley face just above the text box, locate (browse) your photos, click on them, they list, click Upload, click Close This Window, click Submit. Easy enough!

Thanks!

rhettman360

Alright I finally got around to taking a look. I checked my tranny fluid level and It's way overfilled. However the fluid itself looks to be in pretty decent shape.

zxguy1986

I have an extra plenum cover available if you are interested. Nissan 300ZX '84-'89 Plenum Cover
Can give you free shipping.