Hey folks - I've recently revived my 280Z and am working to get it back on the road.

I've drained and replaced the old fuel - there was some sediment present, but I was surprised at how little.

The car turns over and starts easily, and idles like a champ, hovering around 850-900 RPM (it's an automatic, just fyi). However, when throttle is applied, power drops, the car will rev to 1500-3000 RPM or thereabouts and then pop, stutter and basically drop dead back to idle. The car never dies during this time.

The existing fuel pump wails like a banshee. I'm not sure if it's an OEM pump or an aftermarket junker. I do have an aftermarket pump on-hand for temporary use, as I don't have the cash for an OEM pump at this time. But trust me, I'm aware of the opinions on the aftermarket units...

Obviously, it's not drivable in this state, but it's enough that I can putt it around the driveway and garage while I work on it. It's easier to see in the sun, after all.

I'm compiling a list of tests and options. My tool selection is limited and I no longer have my vac or fuel pressure gauges, so I'll need to replace those at the least. Here's what I'm looking at so far:

Replace fuel filter (needs to be done anyway)

Perform vac test, possibly yogurt-cup option

Perform fuel pressure test

Some people have mentioned that the throttle valve switch has been the cause of stumbling like this. The FSM states that it can be continuity tested but you have to judge degrees of movement and it all sounds complicated. Is there a simple way to test this switch, like running the car with the harness disconnected?

When the car stumbles, it voices its displeasure, and sounds like it's backfiring under the hood - I'm pretty confident than my downpipe is rusted out, and that equal parts of the exhaust end up under the hood as that shoot out the back.

I've tried to capture this in a couple of videos that I'll compress and upload tonight when I'm home. They are fairly poor quality, but might be better than nothing.

Sticking a camera under there would give you a look at the filter while the pump is running.

Oooo, that's a thought I hadn't considered. I've got a couple of small cams that would probably work just fine.

I didn't mess with the car last night - got some irritating letters in the mail from Fidelity. A few years ago, when I moved, I took an early retirement withdrawal, and worked out that I'd be ok with the tax hit and the loss of some interest earnings in the short term. I upped my contribution amounts and have already made up the difference, and I'm still quite a long ways off from retirement.

Anyway, long story short, Fidelity processed my withdrawal using sources they shouldn't have (roth money, mostly) and now demand immediate repayment. So I'll be fighting with them quite a bit in the near future, I suspect.

But my plug wires showed up....

OK, success..mostly.

We pulled the in-line filter to pump hose and I sucked a faceful of gas, but we got the filter loaded up with fuel. I put some gas in a squirt bottle and used it to prime the pump itself while it was still on the car. Boom, starts and runs like a champ. It was popping and acting lean again for a few minutes but it leveled off, possibly pushing air out of the lines? I will still have to play around with the AFM to see if I can hit that sweet spot.

New problem though - it doesn't want to shift out of first gear. It's an automatic, and regardless of what I stick it into (D, 2, 1) it won't shift, and there's nothing to make me think that it's starting off in 2 when I put it in 2. The fluid is full and clean red and not burnt smelling. Haven't had much luck searching here or at zcar for anything automatic related - almost everything that comes back in a search is in regards to swapping it for a manual.

Kelly,

How long has it been sitting? Has it shifted since you have started working on it again?

Charles

We pulled the in-line filter to pump hose and I sucked a faceful of gas, but we got the filter loaded up with fuel. I put some gas in a squirt bottle and used it to prime the pump itself while it was still on the car. Boom, starts and runs like a champ. It was popping and acting lean again for a few minutes but it leveled off, possibly pushing air out of the lines? I will still have to play around with the AFM to see if I can hit that sweet spot.

New problem though - it doesn't want to shift out of first gear.

So, on the fuel, it sounds like the filter was blocking gravity flow of fuel to the pump, and the pump was so dry it's rotors were just spinning in air. Interesting fix. You should still check pressure before messing with the AFM. Fuel pressure is the basis of fuel injection. You can waste tons of time if your fuel pressure is not right.

There's a whole chapter specific to the automatic transmission in the FSM. It's the only chapter with color in the diagrams. Also has a very large trouble-shooting chart (not a good sign!) with "failure to shift 1st to 2nd" as one "trouble".

Edited July 14, 201311 yr by Zed Head

Charles - It hasn't shifted since the last time I actually drove it, which was probably 2 years ago. The last time I moved it, I just had it towed to the new house to make things easier.

I agree. I'm just waiting for another paycheck to roll in so I can pick up my own FP tester, rather than waiting for the local Advance to get the one loaner back in stock.

That seems to be exactly what was happening. Without having primed the pump before installing it, the rotor spun air, which wouldn't create a vacuum, since it's not an air-tight seal. Once I filled the filter (and my mouth - I will say it's the one time I have regretted having a beard) and primed the pump with a little squirt bottle, it was off to the races.

I will say that I haven't heard or felt the engine rev as freely or pull as hard since I've owned it. And although I only drove the car around for about half an hour, the little in-line filter is crystal clear with no sign of crud. I know the tank is mostly full and I'll keep an eye on it as it runs lower.

Since it's the first time I've been able to rev freely, I wasn't aware of any transmission problems until yesterday. The first shift point doesn't occur until something like 35MPH, if I remember what the FSM says. Since I couldn't rev past 3k, getting it to 35 was a serious chore.

Still - one problem / solution at a time. I'll get to put my pretty new plug wires on now, and I'll test the fuel pressure and then worry about the stupid transmission. Getting this far has been all thanks to you folks, it has to be said.

Not gonna lie...the AT section of the FSM hurts my brain.

Kelly, congrats on the fuel issue! Making progress!

I don't really know ATs very well, never having owned one except briefly, but I believe they up-shift when the engine vacuum climbs to a certain value. I believe this is done by a "modulator." If your engine isn't running efficiently (probably because of mixture or timing issues), the vacuum might not easily reach that threshold level for up-shifting. That would be my guess. I think you will know a lot more about your engine if you can hook up a cheap vacuum gauge.

I would guess two things about your engine:

1. Running lean (common issue with '78 Z)

2. Stuck/sticking breaker plate in your distributor (i.e. messed up timing). This is a common issue with all Z's.

The vacuum modulator diaphragm seems to be a potential trouble spot on the ATs. I was able to find one helpful post over at zcar (imagine that) stating that a damaged modulator will seep transmission fluid into the vacuum hose connected with it (punctured/torn diaphragm). They seem to be common failure points over time, but my casual searching last night at MSA, Arizona Z and courtesy didn't produce a replacement. I was just wondering about the cost should I find mine to be bad.

The FSM also doesn't indicate where the vacuum line that runs from the transmission modulator leads to on the manifold. I'll be playing around with a flashlight and seeing what I can find.

I should have kept my little vac gauge...when I had so many issues with my F150, I ended up just mounting a little autometer vac gauge in the dash. It would be nice to have now.

EDIT: I just ordered a new vac gauge and a fuel pressure gauge that can handle EFI pressures. I tend to have to accumulate parts and tools rather slowly...

Edited July 16, 201311 yr by Virto

These are essential tools! I'm glad you have them on order.

FAIW, I have a fuel pressure gauge permanently installed in my engine compartment. I picked up a very cheap pressure gauge from the hardware store, screwed it into a T-fitting with a couple of barbs, and installed it inline between the fuel filter and fuel rail. Total cost was something like $10. It's perhaps not dead-on accurate, but it's not bad, and it's always there if I ever find myself stuck on the side of the road.

I agree. I didn't like the idea of leaving one in place, just because I have bad luck, and it's a potential point of (unlikely) failure. I'm re-buying some tools that I've had in the past that have been lost in moves or otherwise misplaced/stolen.

What's the best place to check manifold vac on these motors? Can I just pull the line off the FPR or should I look elsewhere?

I use the brake booster hose bung, it's bigger and easy to get to.