280 running rough

[thelazyman]

I have a 78 280z that I just can't seem to get running right. The car will idle just fine albeit a little rough but when I get it out on the road it seems to sputter under load. Just cruising it seems to be OK not great just OK. But when starting from a dead stop the car will sort of studder. Not sure if that makes sense but it seems like it is choking or something. The engine is just not smooth. And for this reason I can't get it smogged and overall the car is just not realiable. Can anyone help. I am just getting so frustrated with this car. I have put in a new distributor, injectors, altenator, the engine has been completely rebulit. Valves are adjusted. New fuel filter.

I have set the timing to 10 degrees and when I do this I have to rotate the distributor all the way counter clockwise until it stops. I can't get any more than 10 - 12 degrees. This doesn't seem right and even with the timing set the idle is still not right. I give up I just can't figure this thing out. PLEASE HELP!!!

[thelazyman]

Just a followup. I have a fuel pressure gauge installed after the fuel filter and when idling I am seeing about 30 psi. When running under load I am seeing ~40 psi. Is this normal. I am wondering if what I am seeing is due to the engine running too rich. How would I even adjust that.

[thelazyman]

Further followup. Just tried to start the car again and now I am having a problem starting it. I have to pump the pedal to get it running and it will not idle now. I have to keep reving it to get it going. And when I do I am getting alot of black smoke. My fuel pressue is steady at about 30 - 35 psi. And I am getting spark on all cylinders.

[78 280zcar]

Check your dist cap for cracks and let us know if it is OK!

Also do you have any mods on the car such as a bigger throttle body any thing like that?

[Mat M]

Have you checked the mass air sensor? The gate may be stuck/sticking.

[BuDavid]

I guess many things ca cause same kind of $^!#, did u check for vaccume leaks? is your AFM original or from some other car?

I hope that you'll solve it soon..

sorry if the tip won't help..

[78 280zcar]

Dont discourage yourself from the car. Its only a car and you can figure it out, it just takes a little patience! (and lots of beer and cursing) and the ride will pay off for itself.

[DatsunZsRule]

First of all, how are you getting 35 PSI? "I am having a problem starting it. I have to pump the pedal to get it running and it will not idle now. I have to keep reving it to get it going."

You said you had about 30 @ idle before in your second response which is low. If your Z is Stock, it should be maintaining 36.3 @ idle. Do you smell gas at all? Sounds like you got a Fuel Leak somewhere. Check all your rubber fuel lines for any cracks or tired out fuel hose clamps that could be leaking under the hood and under the car where the fuel pump is. Another possible cause could be a vacuum leak somewhere in the system. The Fuel Injected Z's will not tollerate any vac. leaks. Something as simple as a loose oil cap will cause running problems so check for any possible vac. leaks as well. Check your A.F.M. Rubber boots for cracks when looking for vac. leaks. If the A.F.M. boots are cracked, Unmetered air enters which fouls air/fuel mixture because the E.C.U. is operating off of what it's receiving from the A.F.M. (How far the air is moving the flap) and the E.C.U. is unable to compute the extra unmetered air which is what fouls everything up. Hope I made sence. It's tough to explain

Best of luck and don't give up. Patience is the Key

[thelazyman]

Thanks for the feedback everyone. But just to go down the list:

No cracks in Dist cap. All vaccum hoses have been replaced so I don't think Ihave any leaks. All fuel lines have been replaced and I am not seeing any fuel leaks. New Distributor. New fuel filter. New injectors. Timing is set to 10 degrees. Car is all stock with the exception of almost everything being new or replaced.

AFM is original to car and the boots were replaced. So it could indeed be the AFM.

Here is what I know so far. I have spark on all cylinders. I have 30 to 40 psi of fuel pressure (30 at low idle 40 if I rev it). I have fuel and spark and alot of smoke which tells me I don't have enough air. Unfortunately there are so many things with this car that can cause this problem. AFM, ECU, Air regulator, TPS, Air Mixture screw on AFM, some odd loss connection...I guess I am just stuck going back over everything and trying to figure out what it could be. THe last resort will be to take a 20 lb sledge hammer and put it out of it misery.

I know in the end it will be some simple little thing that is causing all of this.

[daddz]

Another possibility which comes from the car sitting for extended periods of time and which may also be causing one of my 280Z's to act strangley is this:

in the fuel tank you may have a clogged pickup; there is a small screen at the end of the pickup and it may well have become clogged. You may end up having to punch through the screen to cure the problem but the gas tank needs to be removed which is sort of a big job.

In my case the 280Z in question is a '77 280Z that has been sitting since April of 2003. It has recently received new Nissan injectors, injector relays, exhaust and intake manifold studs and gasket. I have replaced all of the vacuum lines with silicone hoses from hose techniques. The spark plugs were replaced with NGK BPR6ES11's, new NGK spark plug wires, Nissan dist. cap and rotor and new Nissan air filter. While I was at it the fusible links and covers were replaced and the contacts cleaned while I was at it. I am about to install a new Nissan fuel filter and Nissan fuel pressure regulator as I did not have access to these parts prior to now.

The car would not start for about a week after the initial drive home from the shop. It had stalled on the way home and restarted just fine. Once changing the cap, rotor, wires, etc. it refused to start. After letting it sit for about a week it started and has been doing so for about two weeks. Like yours, mine would stumble on start up and smooth out once given a bit of gas. I will install the parts mentioned above and let you know how it goes. I really do not want to have to drop the gas tank if I can help it.

Good luck.

[78 280zcar]

daddz, do you really own all of those cars on the bottom of your post:surprised and good luck with your 77

[andrewg3300]

Hey, this prolly wont help but, My 73 240 was acting the same way yours is and i thought it was fuel too rich/too lean, but it turned out to be my pionts in the dist. they were burnt out bad. so i changed the pionts and it ran better but there wasnt something right because it would bog down and smoked when i hammered on it. finnaly, i fixed the prob by adjusting the timing back on the dist. it was set way to fast. hope it helps