1986 300zx N/A Misfire help

[FocoZ]

Hey there,

I just picked up a 1986 300zx for $500 and I'm really excited about it. The body is really solid as is the interior. The engine is my only real worry as it runs very rough and is definitely missing. I have very limited mechanical experience, I just started a 2 year ASE program so hopefully down the line diagnosing and fixing something like this will not be a problem at all. I am not prepared to wait that long however, and so here i am asking you guys for some help.

The woman i bought it from said it had been running fine and then she let it sit for about a year before she decided to sell it.

I did a full tuneup, new plate, rotor, cap, wires and plugs, no change to how it is running. The plugs i pulled out looked as if it had been running rich.
i pulled the codes off the ecu and got TPS, EFT and MAF.
When i tested the TPS it wasn't variable resistance at all, just open and closed, is this how it should be?
The Engine Fuel Temp sensor's connector is very corroded, i haven't cleaned it yet, but could this be making it miss? Also the vacuum hose to the FPR is cracked and needs to be replaced.
I haven't done anything with the MAF yet.

I called Nissan and i was informed that there were no open service campaigns for the VIN of so I think that the fuel injectors were done.

I am trying to wrap my head around everything but i feel like i am just running in circles and tying myself it knots, any help or insight you can offer is much appreciated.
Thanks in advance!

[evildky]

Sounds like you're off to a good start. Yes the tps is on off, it's an evolution of the bosch L jetronic system they copied in the 70's. The tps does very little in a metered air system other than regulating the flow of air. The first step is to identify the cylinder (s) misfiring. you can then verify spark at that particular cylinder then verify that injector is firing, if you have spark and fuel that means the problem is a little deeper. Time to test the compression, if that cylinder is low, add a squirt of fresh engine oil and retest, if the numbers come up you have a ring issue, if the numbers do not come up you have a head, or head gasket issue. Does it miss at idle and clear up with rpm? I had a Z32TT that had a stumble at idle that drove me nuts turned out to be a cracked valve seat.

[FocoZ]

Thanks for the info about the TPS Evil! Now i can clean off the contacts and not worry about it.

What is the best way to determine which cylinder(s) are misfiring?

It seems like it picks up another cylinder at around 3k or so, but is still really rough.

I may be able to pick up a compression test gauge, but I think a cylinder leak down test is out of my range at the moment.

Thanks again, any and all ideas are appreciated.

[evildky]

Just unplug one injector at a time while idling, if the rpm drops or the car dies that cylinder works, if not then you found a dead cylinder.