86 Idle Issues

[Jerichowalker]

I just went with a friend to pick up an 86 N/A 300zx with an Auto trans and it on par with buying a 20+ year old vehicle as soon as she gets it home it begins to express its issues The major issue it seems is with the transmission. When in Park or Neutral it idles high at about 1500 rpms, but as soon as you put in drive the rpm drop significantly to a regular idle around 800 rpm. Is it possible that the PO just raised the idle to keep it from stalling out while under load? Could it be the torque converter or similar slushbox black magic or is it an isssue with vacuum/timing? Btw this occurs when the engine is both hot and cold. Its amazing how these things never reveal themselves until after the test drive.

[BunnySlippers]

Its amazing how these things never reveal themselves until after the test drive.

 

Hahaha, yeah, that seems to be the way of it.

 

Check the trans fluid level.

Make sure the timing is set properly.

Bring down the idle while its in neutral to a respectable RPM.

Then see what happens when you put it in gear.

 

Also see if there is anything catching the throttle cable. On 2 of my old Z31's the plastic sleeve around the throttle cable, right at the throttle body, broke apart and caused issues. And make sure that it's not adjusted too tight (pulling the throttle open while the pedal is up)

 

 

And my final thoughts on it, swap a manual in there!

[Jerichowalker]

Yea I'm definately pushing hard for the manual swap. Even though it isnt my car it will save me a lot of work in the long run. Thanks for the response I'll try that out and see if it helps out. I've heard of the throttle cable issue on many of the z31s so Theres a good bet thats making the throttle stick.