jjohart

Hi, I've been talking with the "gurus" on Hybrid Z about an issue I've had with my 83 280ZXT for the past year/since it was I/C'D/CAI/3 inch exhausted.
Basically, in summer, on warm restarts, the car would stumble, near stall and backfire. I used HybridZ's advice, and wired my stock injector fan to a ground post, so that it would ALWAYS run after the car was shut off, rather than just selectively. This seemed to really work, up until this winter, when I noticed a very obnoxious tendency which set in like clockwork at EXACTLY A MINUTE after the car was started from cold, which was/is a completely wimped out throttle (decreaase in power for amount accel. pedal depressed), and then, I SWEAR, ONE MINUTE LATER, the power sapping disappeared/s, as if a hand was squeezing the fuel supply, and then let go.
This condition has definitely worsened, and it seems almost ironically like the summer condition, except that engine fan isn't doing the trick! THE MORE I DRIVE THE CAR, and then leave it off, for even just a minute or two, when I come back, the same wimpy power sapped lean conditions above occur, unless (and in all cases) I even out the fuel supply by revving substantially (in the 2-3000 RPMS range), until I hear the misfire go away at lower revs.
I am wondering if I am going to have to make due with my flippin right foot revving the bejesus out of this car every time it's restarted...obviously it is more of an annoyance than anything that makes the car unable to be driven-at least not yet. There are no decent Z mechanics willing to work on this car other than the local shop who've run AFM, leak, wiring, fuel pressure and all else to try and point this condition to a cause. They replaced the stock regulator with an adjustable FPR and set it to 8psi over stock, but I don't notice any difference, apart from a little more stink in the exhaust.
I should mention that I sometimes heard this detonation noise at high boost, but maybe the higher pressures got rid of that. At any rate, I'm not convinced the next step is to put on lean/rich and/or fuel pressure gauges, and then have them play around with the AFM. I am not into or knowledgeable on working on cars, so technical answers don't help me..what would be great is a good Z mechanic on the East coast, but there aren't any, AFAICT.
In the meantime, is there any kind of fuel assist device I could switch on to provide additional enrichment when the car is doing this, like a "rich" switch on the dash? Is there any fuel management computer that might help, that I can selectively SWITCH ON AND OFF?
This car has had everything brought to new, including plugs/cap/rotor/wires, tune up, swapped ECU, etc, and when it doesn't run like this sputterbucket, it feels like it could go to California and back no sweat. My wife says it's just like me, Dr. Jeckyll/Hyde-like....I do admit that this problem has appeared post intercooler/CAI install, and there are no leaks, but I have heard that other folks have run into poor running post customs like this. Any help appreciated, but again, almost everything has been tested, at great expense to me, and I AM NOT a bloody mechanic, just trying to keep this a tolerable daily driver (it has only 58K miles!)...maybe I'm a bit of a brat figuring I wouldn't have to push the throttle to warm up the freaking fuel supply, like getting a 65 year old to run a marathon before they walk a block in the morning, but I don't understand what's heating up/going lean, etc, just from shutting it off and restarting after its warmed!!
Thanks anyways, in advance!
John-Natick, MA

DoTheDrew888

Just some thoughts...

1. Have you recently replaced the fuel filter?

2. It could be your fuel pump on its last legs.

3. Maybe you have a crappy battery and its starting to give out.

4. Possibly the alternator... maybe.

assimilated420

i would check fuel pump, replace fuel filter...if no change.. then i would goto the alternator..cuz even if the battery begins to crap out the battery serves no purpose but to provide power while engine is off and to start the car...alternator runs evrthing else when running.. and a bad alternator is going to cause numerous problems

lww

I agree with the above. Fuel pump or alternator.

An alternator check should be a relatively cheap test.

The bad or failing alternator can make your electrical system do some pretty funky things both to the computer as well as affecting the injector pulse.

Fuel pump can be had relatively cheap as well with easy replacement as it's mounted on the passenger side outside the gas tank.

Bleach

this is a long shot, but funky electrical can be caused by funky relays. That little black box (front right corner of engine compartment) has some relays in there. They are $50 each from Nissan, but maybe $5 each from a junk yard. Replace those or swap some around and see if the problem goes away.

jjohart

Hi..I spent $50 USD on the fuel filter and no improvement. My contacts are cleaned (past mo.), but IF anyone has a cheap AFM for an 83 280ZXT, please let me know..other than that, I'm prob. going to replace my fuel pump with a Bosch hi-p. pump I've had for a year...if anyone knows of higher powered injectors/fuel rail to do that up...so I get a perf. gain even if I'm wrong about the pump...again, let me know!!!
Thanks
John

RodMoyes

This is the exact same problem being discussed in another post right now... A problem that is happening on cars that are'nt heavily modified, but are mostly stock. I'm having the same deal on my car (1980 n/a). and I absolutly can't figure it out. I have done all I can do to no avail. Not only have I been in the business for 17 years, but a shop full of very qualified techs are at a loss on this one as well. So far... I WILL FIGURE IT OUT.

Rod.

jjohart

Hi Rod, and I appreciate your being aware of the issue...so I don't feel I'm just being picky with a 22 year old car!!! I do however think (which=guess) that the clicking I hear when it's sputtering/bucking, must be the afm door slapping something..but my mechanics took it apart, checked resistance, and said it was ok, but that maybe I should try finding another....it can get very expensive replacing parts as a guess target...but at least I can do the afm myself, weather permitting.
Thanks
John
P.S., which post is similar to my issue?

RodMoyes

See the "won't idle while hot" thread further down in this section...

I'm starting to think this a common 280zx problem, but so far, nobody seems to know the cure. AFM is not it... I switched mine to rule that out. I have a spare fuel pump I'm gonna try and swap that next just to see. I just replaced the Cold start valve hoping that was it, but still it did not change. I know a tiny pinhole leak anywhere between the filter and injectors can cause a post shut-off pressure loss that can cause this, so that's the next thing. I will keep you posted.

Rod.

CWHammer

This started on my '83 AFTER having the fuel pump replaced. It initially started idling irratically but seemed to "go away" after awhile. I assumed it was some cavetation with the new pump. However, it came back, slowly getting worse. Now it sputters when started, I hit the gas once and it smoothes right out until the engine warms up. Then all hell breaks loose. The car actually dies when I stop. I can run the turnpike at 80 and watch the tach jump up 200 to 800 RPM with no audible changes or surges. I was wondering if anyone has tried the throttle position sensor? I have injectors on order and I noticed the hoses are dry rotted. They look original.

CWHammer

Now I'm really confused. The car stalled while waiting to turn into the parking lot at work tonight but idled perfectly when I pulled into a parking space. Any suggestions for an intermittant idle problem?

The pump was replaced at the Nissan dealer supposedly with an OE pump and filter. Since the last post I've changed the plugs, Ign. Con. Mod., wires, injectors with onlty a slight improvement with the injectors. I know the dizzy needs work which I can get a reman for $189. This starting to get expensive!! I'm off for the next three days and I hope to find something to help everyone out.

Hey Rod, anything from your end yet?

Heat Rave R

What kind of pump did you replace it with?

jjohart

Hi
for the fellows who are looking at a problem with the car dying underway, a local garage trying to convince me they can cure the problem made mention of a TS bulletin on such a mid throttle stall condition.
My car ALWAYS starts fine...nice new battery...but I just can't understand what goes on at first start of the day...it almost seems like something suddenly kicks in with a hell of a damping/sputter/stall effect, then it goes away, almost exactly a min later.
I swapped ECU, to no effect. I may do the fuel pump replacement with a Bosch high pressure unit. There was also a helpful fellolw who told me my thermo time sensor could be messing up the ECU...my mechanic said that wouldn't have any effect (I tied the injector fan wire to ground to ease up on summer "heat soak" condition, which worked til this winter!). The fellow says even his normal thermo time switch is wired back to the ECU...my mechanic disagrees.
Finally, what I don't understand is whether there's anything that can control this...as it is now, it's a handfull on every restart, and no one else but me is used to it enough to drive it safely...I can literally drive off and have the sputters, unless I do a full WOT REV!
How does a mechanic check fuel leaks/vac leaks?
THanks
JOhn