OK: THis project has been a real bitch, but now it runs and sounds real good, except for a little fart now and then at idle, and it seems like all the way thru the rpms. I have three new injectors, 3 original ones, and a cold start valve of dubious origin. NO vacuum leaks, but the other thing is, a while back I had the fuel rail out, coil wire disconnected, and was cranking the engine to make sure all the injectors fired, and they did, but they all fired at the same time! WTF? I thought we were batch fire! Oh, is it 3 batches of 2, or 2 of 3? Am I one of the few unlucky bastards who actually needs a new ECU? or could it be the dropping resistor? J or one of the other FI gurus, this is seriously pissing me off. I just replaced intake gasket, ported/polished intake, pacesetter header that I made fit after hours upon hours of grinding, filing, measuring, welding. even got the EGR hooked up properly. Its always had a little fart-miss at idle, but now there is no excuse!

 

Have you replaced your injector connectors? One of your connectors may be faulty which would could cause an intermittent break in the circuit to that injector. This would cause the problem your experiencing. If you haven't replaced you injector connectors yet then this might be the right time to do so. If you did already replaced them check to make sure a solder joint or butt connector isn't coming apart (I've had this happen to me).

If the miss is constant and never goes away then its possible you've got a valve thats stuck open.

 

I think this is a common 280zx issue. I had that on the NA and turbo but only at idle. No hessitation at high rpm.

its very subtile though. you can hear the stumble but the rpm needle stays steady.

 

I have replaced all the injector connectors, wiggled them all while running, no change. What about all the injectors firing at once? they arent supposed to, right? the miss is like every second or so, its just weird.

 

280zx injectors are BATCH FIRE. Have you hooked up an air/fuel ratio gauge to see what the status be when it misses?

 

like nismopick said, check the air fuel ratio, and also what is your timing, it should be about 10 degrees for that car, and idle at 800 rpm. it sounds to me as if it is running rich. and check your thermotime switch, it controls the computers inrichment cycle, if it thinks its cold all the time, it will run a little rich.

 

If the day ever comes that my car idles completely smooth... I'll sell the S.O.B. cuz that will mean it's gonna die any minute!!!!!!!!!!!!!!!!!!!

I have heard tales of smooth idling S130 cars, but I rank them right up there with Bigfoot, the Loch Ness Monster and a good Janet Jackson song... Sure, it could happen, but nobody can document proof!


Rod.

 

Mine runs pretty smooth, once he is warmed up. Pretty steady idle, much better than my '81 ever was.

 

It's not just an idle problem though. He said it goes all the way through the rev range. And it's happens "every now and then", so it's not a constant problem.

correct me if I misunderstood jmmorriso

 

"It's Miss Jackson, if your nasty"



bob

 

its just an occasional fart, not a pop or backfire, just a little flatspot in the exhaust note, especiallt noticeable with an uncapped header(no im not driving it like that) waiting on a new cat. Hey, if my shops racecars can idle smooth with Holleys and lumpy cams and 13:1 compression, theres no reason for a FI zx with stock cam and no vacuum leaks not to idle smooth. Engines are stupid, and they dont know what cars they are in, you can tell your l28 its a ferrari v-12, and it should believe you. Im gonna go have a chat with my car.

 

Oh, I almost forgot, are all six injectors supposed to fire at once or not?

 

I'm thinkin' you have a spark issue.

In order of least expensive to most expensive:

1. Re-gap your plugs
2. Verify your timing
3. replace your cap and rotor with Nissan OEM
4. Get new NGK BP6ES spark plugs
5. Get a set of Magnecor KV85 spark plug wires
6. Get a Nissan OEM '84 to '89 300ZX Turbo coil

Don't do these all at once, but start at the top, make each change and see if it improves.

Good luck.

 

they do fire 3 at a time i believe, thats what makes them batch, its a good system, it just is very outdated. and my car idles smooth, you just gotta have luck, that all, just dumb luck. timing and air fuel mixture at idle play a large role in that, now if a sensor is screwed, well then you get a crappy idle.

 

If they were all firing at once that might just be for start up. Once the car is started it should go into a batch of 3 cylinders at a time.

 

My 2+2 used to idling perfectly. It was soooo smooth. With no missing or anthing, but that didn't end well when I samshed it up... SEE LET THIS BE PROOF! People aren't allowed to have a perfectly idling S130. If it idles perfectly you better find someway to make it idle not so perfect or like Rod says, sell it instantly!

 

I know the ignition is cherry, Ive got Accel wires, new autolite plugs Kem, or Airtex cap and rotor with no tracking or anything on it. I think its a Crane flamethrower coil, Im running a ballast resistor on it, but I dont think its necessary. What would happen if its supposed to have one and I remove it, blow the coil? Whats so special about a 300zxt coil and oem cap/ rotor? I put the cheapo plugs in it because the NGKs had too much piston speckles on them from overheating. The autolites are a lot colder (not platinum).

 

what do you think about wiring an LED onto each injector to find out? It would look uh, interesting at night

 

Blasphemy!!! Use NGK's... That is what Nissan advises to use. You can get them from Napa for about $1/piece. Autolites are about as crappy as you can get.

 

Those do already exist... they are called injector noids...

http://www.midwayautosupply.com/deta...iption.asp?831

 

$1 ? No damn way! I'll check it out tomorrow.

 

http://www.partsamerica.com/ProductD...pe=960&ptset=A

 

I have noid lights, i was talking about wiring leds inline so I can watch them all fire with the engine running. I didnt think there was such a thing as a $1 spark plug any more, thanks L-dub

 

my car also idled perfect way back in the day... back when it had the original injectors and under 150K miles. Then I started swapping on headers, throttle body, K&N, and I had to replace the injectors. Its never been the same since.

Both my NA and turbo engine have that ever so slight miss at idle.